Research Article
Received: 27 January 2023 Revised: 27 May 2023 Accepted article published: 13 July 2023 Published online in Wiley Online Library:
(wileyonlinelibrary.com) DOI 10.1002/jsfa.12835
Food quality profile of pounded yam and
implications for yam breeding
Bolanle Otegbayo,a* Oroniran Oluyinka,a Abiola R. Tanimola,a
Fawehinmi Bisi,a Alamu Ayomide,a Bolaji Tomilola,a Tessy Madu,b
Benjamin Okoye,b Ugo Chijioke,b Miriam Ofoeze,b
Emmanuel Oladeji Alamu,c Michael Adesokan,c Oluwatoyin Ayetigbo,d
Alexandre Bouniol,d Imayath DJibril-Mousa,e Laurent Adinsi,e,f
Noël Akissoe,e Denis Cornet,d* Parterne Agre,c Asfaw Asrat Amele,c
Jude Obidiegwub and Busie Maziya-Dixonc
Abstract
BACKGROUND: Assessment of the key preferred quality traits in pounded yam, a popularly consumed yam food product in West
Africa, is often done through sensory evaluation. Such assessment is time-consuming and results may be biased. Therefore, there
is a need to develop objective, high-throughputmethods to predict the quality of consumer-preferred traits in pounded yam. This
study focused on how key quality traits in pounded yam proposed to yam breeders were determined, measured by biophysical
and biochemical methods, in order to shorten the breeding selection cycle through adoption of these methods by breeders.
RESULTS: Consumer tests and sensoryquantitativedescriptive analysis (QDA) validated thatpreferredpriorityquality traits inpounded
yamwere related to textural quality (smooth, stretchable,moldable, slightly stickyandmoderatelyhard) andcolor (white, creamor light
yellow). There were significant correlations between sensory textural quality attributes cohesiveness/moldability, hardness, and adhe-
siveness/stickiness, with textural quality measurements from instrumental texture profile analysis (TPA). Color measurement parame-
ters (L*, a*, and b*) with chromameter agreed with that of sensory evaluation and can replace the sensory panel approach. The
smoothness (R2 = 1.00), stickiness (R2 = 1.00), stretchability (R2 = 1.00), hardness (R2 = 0.99), and moldability (R2 = 0.53) of pounded
yam samples can be predicted by the starch, amylose, and protein contents of yam tubers estimated by near-infrared spectroscopy.
CONCLUSION: TPA and Hunter colorimeter can be used as medium-high throughput methods to evaluate the textural quality
and color of pounded yam in place of the sensory panelists.
© 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of
Chemical Industry.
Supporting information may be found in the online version of this article.
Keywords: pounded yam; color; textural quality; texture profile analysis; chromameter; consumer preferences
INTRODUCTION * Correspondence to: D Cornet, CIRAD, UMR QUALISUD, F-34398 Montpellier,
Yam, Dioscorea (spp.) is one of the most important non-cereal France, E-mail: denis.cornet@cirad.fr; or B Otegbayo, Food Science and Technology
staple foods in West Africa.1 There are many species widely culti- Program, Bowen University, Iwo, Nigeria, E-mail: bolanle.otegbayo@bowen.edu.ng
vated in Central and West Africa, especially the yam zone of West a Food Science and Technology Program, Bowen University, Iwo, Nigeria
Africa, which includes Nigeria, Ghana, Togo, Côte d'Ivoire and the
Republic of Benin.2-4 In Nigeria, it is an integral component of food b National Root Crops Research Institute, Umuahia, Nigeria
consumption and agricultural sales.5
c International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria
Yam is consumed in various forms, such as roasted, boiled,
pounded, chips, flour and fried in the yam zone of West Africa, d CIRAD, UMR QUALISUD, Montpellier, France
but pounded yam is the predominant traditional way of consum-
ing it in the region. Pounded yam is made traditionally by peeling e Faculté des Sciences Agronomiques, Université d'Abomey-Calavi, Cotonou, Benin
the yam tubers, cutting them into small pieces, and boiling, fol- f Ecole des Sciences et Techniques de Conservation et de Transformation des Pro-
lowed by pounding into a glutinous dough with mortar and duits Agricoles, Université Nationale d'Agriculture, Sakété, Benin
© 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any
medium, provided the original work is properly cited.
1
www.soci.org B Otegbayo et al.
pestle.6-8 The quality of raw yam tubers is vital for the acceptabil- samples that were used for consumer testing were prepared from
ity of yam food products by farmers, processors and consumers.4 the four landraces – D. rotundata: Lasinrin, Awana, Gbongi-Kamilu
A consumer of pounded yam will usually examine the product for and D. alata: Ewura. In southeast Nigeria – D. rotundata:
palatability by assessing the hand feel and color before consider- TDr11/0010 TDr1100497 and D. alata: TDa1100477, TDa1100203
ing the taste or aroma of the product. Any defect in these attri- were used and in the Republic of Benin six D. rotundata varieties
butes may negatively impact the acceptability of the product by (Laboko, Kratchi, Kodjèwé, Wété, Dodo, Irindou) and one D. alata
the consumer.7,9-11 variety (Aga) were used.
A study12 identified textural quality and color as the critical user-
preferred quality traits for pounded yam acceptability by the Methods
stakeholders, including farmers, processors, and consumers. Key Pounded yam sample preparation
textural quality attributes identified were hardness cohesiveness, Pounded yam samples were prepared as reported in RTBfoods
adhesiveness, stretchability, and smoothness.12 These attributes standard operating procedure.14
can provide potential selection metrics in breeding programs for
yam varieties targeting consumers' expectations for good pound- Yam flour sample preparation
ing quality.
The yam flour samples for biochemical analyses were prepared by
Assessment of food quality of pounded yam in the past, to feed
the method of Otegbayo et al.15 Tubers were peeled, washed and
back to breeders, has relied mainly on evaluation by sensory pan-
cut into longitudinal sections. These was diced into very small
elists. Sensory evaluation, though subjective, has been the most
cubes and dried at 60 °C for 72 h in a hot air oven (Memmert
critical aspect of varietal development after all the essential agro-
oven). The samples were then milled to pass through a 20 mesh
nomic features have been established.13 Sensory evaluation is a
screen. They were then used for chemical analyses.
significant determinant of consumers' acceptability and subse-
quent adoption of new yam varieties; however, apart from being
somewhat subjective it is time-consuming and expensive. Hence Consumer studies
there is a need to develop high-throughput methods to charac- This study aimed to understand the way consumers assess the
terize the quality indicators in yam tubers that can reliably predict quality characteristics of yam food products and the quality
the quality traits of preferred pounded yam. attributes associated with the consumers' preferred and non-
In this study, we present the perception of consumers on key preferred pounded yam. The consumer preference study was car-
preferred quality traits in pounded yam from Nigeria and the ried out on pounded yam samples as described by Forsythe
Republic of Benin and link them to laboratory methods that can et al.16 in two pounded yam consuming countries; Nigeria and
be used to predict these traits. This will help speed up the selec- Republic of Benin. In Nigeria: southwest – Osun state (174 con-
tion decision in the yam breeding cycle and enable yam breeders sumers: 109 women, 65 men),17 south-east – Ebonyi state
to breed for end-user preferences efficiently (a major objective of (150 consumers: 70 men, 80 women).18 In Dassa center Republic
the RTBfoods project). Hence this is an index study that focuses on of Benin (99 consumers: 51 men, 48 women).
what and how key quality traits in pounded yam (color and tex- The three-point ‘Just-About-Right’ (JAR) scale and the Check-All-
tural quality) proposed to breeders were determined, measured That-Apply (CATA) approach were used16 for each of the pounded
by high or mid-throughput methods to shorten the breeding yam samples. Some examples of the JAR scale are: 1 = ‘too soft’,
selection cycle and the perception and adoption of these ‘too dark’, ‘not enough’, 2 = ‘Just-About-Right’ and 3 = ‘too hard’,
methods by yam breeders. ‘too stretchable’, ‘too sticky’. The three-point JAR scale showed
which sensory characteristics of the product are acceptable or
MATERIALS AND METHODS not, and also why the consumers liked or do not like a product.
CATA approach helps to describe the pounded yam sample and
Materials indicates the sensory and perception of descriptors of each sam-
A total of 28 yam genotypes representing white Guinea yam ples as presented to the respondents. In all the study regions
(Dioscorea rotundata) and water or greater yam (Dioscorea alata) (southwest and southeast Nigeria and Republic of Benin),
were used for this study. Seventeen breeding lines (eight pounded yam samples were prepared from yam varieties with
D. alata genotypes and nine D. rotundata genotypes) were variable food quality attributes (preferred and less-preferred).
obtained from yam breeding programs of the International Insti-
tute of Tropical Agriculture (IITA) and National Root Crop Research
Sensory quantitative descriptive analysis (QDA)
Institute (NRCRI), Nigeria, and 11 landrace cultivars. Four of these
[three D. rotundata (Lasinrin, Awana, Gbongi-Kamilu) and one The QDA was carried out on pounded yam samples made from
D. alata (Ewura)] were collected from a contact farmer's field from other 13 yam genotypes/breeding lines (described in the Mate-
Iwo, Osun state, Nigeria. The remaining seven [six D. rotundata rials and method section) from southwest Nigeria as described
varieties (Laboko, Kratchi, Kodjèwé, Wété, Dodo, Irindou) and one in RTBfoods standard operating procedure on sensory characteri-
zation14D. alata variety (Aga)] were obtained from an experimental plot at using 12 trained panelists.
the AfricaYam project, Benin station, Republic of Benin. Out of the
total 28 yam genotypes, 15 cultivars were used for consumer stud- Biophysical analyses
ies, the remaining 13 genotypes were used for sensory quantitative Instrumental texture profile analysis (TPA)
descriptive analysis (QDA) and other biophysical analyses reported This was done through a texture analyzer (TVT 6700; Perten Instru-
in the study – D. rotundata: TDr1401593, TDr1000048, TDr1400359, ments, instrumentvagen31 Hargensten Sweden) using the tex-
TDr0900067, TDr1100180, TDr1401419, TDr IGN 21 (Igangan) and ture profile analysis (TPA) method described in the RTBfoods
D. alata: TDa1400301, TDa1100224. TDa1215201, TDa1100432, standard operation procedure.17 The parameters measured were
TDa1100201, TDa1100316. In southwest Nigeria, pounded yam hardness, adhesiveness, stringiness and cohesiveness.
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Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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Color and Gbongi-Kamilu) and negatively by the terms such as ‘slightly
Instrumental color evaluation (L*, a* and b*) of the fresh yam sam- sticky’, ‘slightly stretchable’, related to the least liked pounded
ples and pounded yam was carried out by means of the Hunter yam sample (Ewura). Axis 2 was mainly explained positively by
colorimeter (CR410; Konica Minolta, Tokyo, Japan). The CIE the terms such as ‘white’ and ‘not sticky’ (Awana and Gbongi-
(Commission Internationale de l'Eclairage) tristimulus L* a* b*, Kamilu), and negatively by the terms such as ‘hard’, ‘lumps’, ‘not
where L* (lightness) axis – 0 is black and 100 is white; a* (red- stretchable’, ‘gray’, ‘bland taste’, ‘not moldable’ and ‘bad aroma’
green) axis – positive values are red while negative values are (Ewura). On the right part of the PCA plot, highmean overall liking
green and 0 is neutral; b* (yellow-blue) axis – positive values scored by consumers was related to the high-quality characteris-
are yellow, while negative values are blue and 0 is neutral. The tics such as ‘stretchable’, ‘no lumps’, ‘sweet taste’, ‘soft’, ‘good
method of Alamu et al.19 was adapted and color was evaluated aroma’, and ‘smooth’, which were associated with the most liked
both immediately after cutting the yam tubers (0 min) and 10 min pounded yam samples from varieties Lasinrin, Awana, and
after. Gbongi-Kamilu. A high mean overall liking scored by consumers
was related to the high-quality characteristics such as ‘white’,
Biochemical composition ‘not sticky’, (on the left part of the PCA plot), which were associ-
The polyphenol oxidase (PPO) enzyme activity of the yam geno- ated with the most liked pounded samples, made from good
types was determined as described by Omidiji and Okpuzor.20 yam varieties, Awana and Gbongi-Kamilu. While at the opposite,
This was done to determine the browning rate of the yam tubers. a low mean overall liking by the consumers was related to the
Starch, sugar, protein, dry matter, fat, phytate and tannin were low-quality characteristics such as ‘gray’, ‘bitter taste’, ‘sticky’
determined from the yam flour using near-infrared spectroscopy (as on the left part of the PCA plot), which were associated with
(NIRS) as described by Alamu et al.19 the least liked pounded yam variety Ewura.
Pounded yam samples from different varieties were perceptibly
Ethical consideration different in terms of their food quality attributes as rated by the
This study was approved by the National Research Ethics Commit- consumers. The textural attributes associated with a preferred
tee and Bowen University Research and Ethics Committee pounded yam were ‘stretchable’, ‘soft’, ‘smooth’, ‘moldable’, ‘not
(BUREC) approval 2020 prior to fieldwork. Consent from sensory sticky’, ‘white/yellow’ depending on the yam flesh color, ‘sweet
panellists and from consumers participating in this study was taste’ and ‘good aroma’ (Fig. 1 and Supporting Information
obtained, and the research respected the rules of voluntary partic- Fig. S1). These attributes described pounded yam varieties Lasin-
ipation and anonymity. rin, Gbongi-Kamilu and Awana. In terms of stretchability, Awana
was rated as more stretchable than Lasinrin followed by Gbongi-
Statistical analysis Kamilu. These samples were also described as being smooth
Statistical analyses consisting of one-way and two-way analysis of andmoldable. Generally, Lasinrin was rated as themost moldable.
variance (ANOVA), bivariate correlations, discriminant analysis and The color and hardness of pounded yam samples from Awana,
hierarchical classification were conducted on the data generated, Gbongi-Kamilu and Lasinrin were ‘Just about right’. The least liked
to determine: (i) the correlation between the biochemical composi- pounded yam sample was from Ewura (D. alata) as it had the low-
tion of yam varieties and sensory attributes of pounded yam that est mean overall liking score (Table 1, Figs 1 and S1) mainly
may serve as intrinsic quality indicators for the textural quality of because it was ‘lumpy’, ‘not moldable’, ‘too dark’ in appearance
pounded yam; (ii) the correlation between TPA andQDAwas estab- and had a ‘bitter’ taste by consumers in the JAR test.
lished; and (iii) correlation between consumer acceptance (JAR test)
and QDA of the pounded yam samples for the establishment of Southeast Nigeria
acceptability thresholds. Linear multiple regressions were applied The consumer acceptability result of pounded yam from the
to predict the sensory attributes by biophysical parameters. The southeast was very similar to that of the southwest. The least
best model limited to two parameters/variables was selected. In ‘liked,’ or preferred product was from the water yam clone,
these conditions, a high coefficient of determination (R2) between TDa1100477; it had the lowest mean overall liking score (Table 1)
predicted and observed variables was considered to assess the because it was described as having ‘lumps’, ‘sticky’, and ‘not stret-
quality of the model. All analyses were performed using XLSTAT chy’ by the consumers (JAR test). Favorable terms such as ‘sweet
(version 2016.02.28451; Addinsoft, Paris, France). taste,’ ‘not sticky,’ ‘no lumps,’ and negative terms including
‘lumps,’ ‘sticky,’ ‘not stretchy,’ ‘too dark,’ and ‘not smooth’ were
related to the D. rotundata breeding lines TDr11/0010 and
RESULTS TDr1100497. Interestingly, among the D. alata breeding lines,
Consumer acceptability test TDa1100203 was the most liked (Table 1) because it was ‘easy to
Southwest Nigeria swallow’, ‘easy to cut’, ‘moldable’, and had a pleasing aroma (Fig. 1).
Principal component analysis (PCA) was used to summarize the
relationships between CATA sensory characteristics of Republic of Benin
the pounded yam samples and mean overall liking of each prod- The overall liking of pounded yam significantly differed between
uct scored by all the consumers. The PCA plot for the consumers the seven varieties (P < 0.05) (Table 1). Laboko and Kratchi
explained 95.4% of the variance of the sensory characteristics, were the most liked varieties by consumers (score above 7.8: like
with the first and second axes accounting for 72.6% and 22.8%, very much), while Aga scored the least (4.1: dislike slightly). A seg-
respectively. The loading of sensory characteristics on PCA plot mentation of pounded yam samples into groups of similar overall
for the consumers (Fig. 1) showed that Axis 1 was mainly liking through an agglomerative hierarchical clustering showed
explained positively with terms like yellow, moldable, stretchable, that the yam varieties were clustered into three groups, as illus-
no lumps sweet taste, smooth, soft, cream, and good aromawhich trated in Fig. 1. Thus, Dodo and Irindou varieties (scored around
describes the most liked pounded yam samples (Lasinrin, Awana 6: like slightly) were considered as making pounded yam of
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Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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Variables (axes F1 and F2 : 81,05 %) Observations (axes F1 and F2 : 81,05 %)
Yellow
1 Sweet taste
80
BrNoowtnscky TDR
0.75 Hard
Good 60 1100497
Aracve
Not drawy aroma
0.5 No lumps 40
Easy to cut
0.25 20 TDA
Milk/cream SmSoooth
Mouldabilit 1100203
0 Modyerately 0
so
-0.L2u5mpWs hite -20
Easy to TDA
swallow Stretchable
Starchy 1100477
-0.5 Scky Too so -40
Heavy TDR
Easy to weight -60 11/0010
-0.75 pounNdo spot
Dark/Dull -80
-1 Bad colour -100 -50 0 50 100
-1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1 F1 (57,37 %)
F1 (57,37 %)
Variables acves Observaons acves
(a)
Variables (axes F1 and F2: 95.36 %) Observaons (axes F1 and F2: 95.36 %)
1 Scky 150
Yellow
0.75
Stretchable Lasinrin
100
0.5
Too soHard 50
0.25
TNoootha
Nrdot smooth Moderately Ewura
mouLludmabples hard
0
Grey Mouldable 0
Not Smooth
-0st.r2e5tchable
ModSelirgahttellyyscky Awana
-50
soEasyBier taste Stoligphotulynd-0.5 Gbongi
Ssotretchable kamilu
Not scky -100
-0.75 Cream
White
-1 -150
-1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1
F1 (72.56 %) -250 -200 -150 -100 -50 0 50 100 150 200
Active variables Supplementary variables F1 (72.56 %)
(b)
300
250
200
150
100
50
0
(c)
Figure 1. Mapping of the sensory characteristics and the overall liking of the product samples by consumers. (a) Consumers from southeast Nigeria; the
second box represents yam genotypes associated with sensory attributes represented in the principal component analysis (PCA). (b) Consumers from
southwest Nigeria; the second box represents yam genotypes associated with sensory attributes represented in the PCA. (c) Hierarchical clustering of
pounded yam samples made from landraces varieties based on consumers' overall liking in Republic of Benin.
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Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
F2 (22.80 %) F2 (23,68 %)
Dissimilarity
Laboko
Kratchi
Kodjèwé
Wété
F2 (22.80 %) F2 (23,68 %)
Aga
Dodo
Irindou
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Indicators for preferred quality pounded yam www.soci.org
Table 1. Overall liking scores for pounded yam samples from yam varieties
Nigeria Republic of Benin
Mean overall Mean overall
Southwest varieties liking score Southeast varieties liking score Dassa varieties Mean overall liking score
Ewura 4.2a TDa1100477 4.7a Aga 4.1d
Awana 7.1b TDr11/0010 6.1b Dodo 6.0c
Gbongi-Kamilu 7.2b TDr1100497 6.4b Irindou 6.2c
Lasinrin 7.2b TDa1100203 6.6b Kodjèwé 7.4b
Kratchi 7.9a
Laboko 8.0a
Wété 7.3b
Note: Means with the same superscript letter in the same column are not significantly different at P < 0.05.
Table 2. Descriptive sensory evaluation of pounded yam from varieties of landraces (Dioscorea rotundata and Dioscorea alata species)
Varieties Smoothness Adhesiveness/stickiness Moldability/cohesiveness Stretchability Hardness Color
Lasinrin (TDr) 9.83a 2.72b 9.39a 4.83a 6.17ab 4.28a
Kamilu (TDr) 9.45a 2.15b 7.60a 1.55b 7.55a 3.95a
Awanah (TDr) 9.35a 5.00a 9.15a 5.60a 5.35a 2.35b
Ewura (TDa) 3.11b 2.00b 3.11b 0.33b 5.72a 4.61a
Mean 7.94 2.97 7.31 3.08 6.20 3.80
Standard error 1.61 0.70 1.46 1.27 0.48 0.50
Note: Means with the same superscript letter in the same column are not significantly different at P < 0.05.Smoothness: no lumps, 10; small lumps, 5;
big lumps, 0. Adhesiveness/stickiness: non-sticky, 0; slightly sticky, 5; sticky, 10. Moldability: not moldable, 0; slightly moldable, 5; moldable, 10.
Stretchability: not stretchable, 0; slightly stretchable, 5; stretchable, 10. Hardness: very soft, 0; soft, 2; slightly soft, 4; slightly hard, 6; hard, 8; very hard,
10. Color: white, 1; off-white, 2; cream color, 3; light yellow, 4; yellow, 5; light gray, 6; gray, 7; light brown, 8; brown, 9.
Table 3. Descriptive sensory evaluation of pounded yam from varieties of Dioscorea rotundata and Dioscorea alata species
Adhesiveness/ Moldability/
Varieties Smoothness stickiness cohesiveness Stretchability Hardness Color
Dioscorea rotundata
TDr1401593 0.29d 3.83b 2.54e 1.00e 5.13a 4.29a
TDr1000048 0.73c 3.68bc 7.23d 2.95d 3.82bc 2.73b
TDr1400359 0.63c 3.37bc 7.13d 4.47c 2.20d 2.83b
TDr0900067 1.27a 3.13c 6.93d 4.40c 2.60d 2.43b
TDr1100180 0.64c 2.45d 8.14c 3.00d 5.14a 4.55a
TDr1401419 1.00b 2.54d 9.04b 6.25b 4.33b 1.92c
TDr IGN 21 0.00e 6.17a 9.42a 8.21a 3.38c 4.54a
Mean 0.65b 3.60a 7.20a 4.33a 3.80a 3.33a
Standard error 0.16 0.47 0.86 0.89 0.44 0.42
Dioscorea alata
TDa1400301 2.04c 2.81c 1.77b 0.08b 6.35b 2.77a
TDa1100224 1.09d 6.82a 2.32b 0.32b 1.18d 1.32c
TDa1215201 3.86b 5.68b 5.27a 2.23a 2.86c 2.64a
TDa1100432 4.53a 2.97c 0.73c 0.27b 6.70b 1.27c
TDa1100201 4.83a 2.71c 1.75b 0.08b 7.50a 1.71b
TDa1100316 1.75c 2.67c 2.13b 0.42b 6.71b 1.71b
Mean 3.02a 3.94a 2.33b 0.56b 5.22a 1.90b
Standard error 0.65 0.75 0.63 0.34 1.04 0.27
Note: Means with the same superscript letter in the same column under yam genotypes (D. rotundata and D. alata) are not significantly different at
P < 0.05.Smoothness: no lumps, 10; small lumps, 5; big lumps, 0. Adhesiveness/stickiness: non-sticky, 0; slightly sticky, 5; sticky, 10. Moldability: not
moldable, 0; slightly moldable, 5; moldable, 10. Stretchability: not stretchable, 0; slightly stretchable, 5; stretchable, 10. Hardness: very soft, 0; soft,
2; slightly soft, 4; slightly hard, 6; hard, 8; very hard, 10. Color: white, 1; off-white, 2; cream color, 3; light yellow, 4; yellow, 5; light gray, 6; gray, 7; light
brown, 8; brown, 9.
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Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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www.soci.org B Otegbayo et al.
intermediate quality, while Aga was defined as making poor- Correlation between QDA and consumer testing
quality pounded yam. Pounded yam made from Laboko, Kratchi, The QDA and the consumer testing results of the pounded yam
Kodjèwé and Wété varieties (scored above 7: like) were qualified samples from landraces from southwest Nigeria were correlated
as preferred good quality. to validate the food quality attributes of pounded yam. There
were correlations (Fig. 2) between the QDA and consumer testing
in terms of smoothness (R2 = 0.99), stretchability (R2 = 0.94), mold-
Sensory quantitative descriptive analysis (QDA) ability (R2 = 0.98), stickiness (R2 = 0.64), color (R2 = 0.85 but there
The trained panelists described pounded yam samples from seven was no significant correlation (P > 0.05) between them in terms
clones ofD. rotundata varieties as smoother, more moldable (cohe- of the softness/hardness (R2 = 0.31) of the pounded yam samples.
sive) and more stretchable when compared with those of D. alata
genotypes (six clones) (Tables 2 and 3). They were also firmer/ Instrumental texture profile analysis (TPA)
harder than D. alata, in the range of soft to slightly soft. Color The results of TPA on the pounded yam samples showed that
of D. rotundata varieties ranged between cream and light yellow, those from D. rotundata were harder, more cohesive and less
while those of D. alata species were off-white (Tables 2 and 3). adhesive than pounded yam samples made from D. alata
Figure 2. Correlations between consumer preferences and sensory quantitative descriptive analysis (QDA) from southwest Nigeria.
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Table 4. Instrumental texture profile analysis (TPA) measurements of pounded yam samples
Stiffness/ Adhesiveness Stringiness
Varieties Hardness (g) (g.mm) Stickiness (g) (mm) Resilience Cohesiveness Springiness
Dioscorea rotundata†
TDr1401593 7178b −1166b −1023bc 0.99a 0.05b 0.12a 0.99a
TDr1000048 6734b −1513bc −1383d 0.94abc 0.03c 0.12a 0.94abc
TDr1400359 4357a −1305b −904b 0.77c 0.01d 0.13a 0.77c
TDr0900067 6397b −1833c −1181cd 0.95ab 0.03c 0.18b 0.95ab
TDr1100180 8962a −436a −580a 0.97a 0.07a 0.13a 0.97a
TDr1401419 6398b −2917d −1722e 0.99a −0.01e 0.18b 0.99a
TDr IGN 21 5091a −1920c −1230cd 0.79bc 0.00de 0.20a 0.79bc
Mean 6445a −1584a −1146a 0.91a 0.02a 0.15a 0.91a
Standard error 559.65 289.80 137.21 0.04 0.01 0.01 0.04
Dioscorea alata†
TDa1400301 5796a −731a −1042b 0.91a 0.03a 0.08bc 0.91a
TDa1100224 3562a −733a −530a 0.95a 0.01ab 0.06c 0.95a
TDa1215201 4694bc −1362bc −1102b 0.97a 0.014ab 0.13a 0.97a
TDa1100432 4188b −974ab −1010b 0.99a 0.01ab 0.09b 0.99a
TDa1100201 4986b −1693c −1340c 0.99a −0.01bc 0.08bc 0.99a
TDa1100316 4970b −2482d −1412c 0.97a −0.02c 0.13a 0.97a
Mean 4699b −1329a −1073a 0.96a 0.01a 0.09b 0.96a
Standard error 311.6 277.1 127.3 0.01 0.01 0.01 0.01
Landraces‡
Lasinrin (TDr) 9812a −2272a −1927c 1.00a 0.03a 0.18bc 0.04c
Kamilu (TDr) 4463d −4815b −1366b 1.00a 0.02a 0.41a 0.08a
Awanah (TDr) 9159b −5126b −2544d 1.00a 0.01a 0.21b 0.05ab
Ewura (TDa) 5436c −1539a −988a 0.98b 0.01a 0.08c 0.05ab
Mean 6933 −3730 −1716 1.00 0.00 0.24 1.00
† Means with the same superscript letter in the same column under yam genotypes (D. rotundata and D. alata) are not significantly different
at P < 0.05.
‡ Means with the same superscript letter in the same column under Landraces are not significantly different at P < 0.05.
genotypes (Table 4). This agrees with previous authors.6,22,23 The between TPA cohesiveness and QDA stretchability. The magni-
TPA could also discriminate between the textural quality of tude of correlations increased when both D. alata and
pounded yam samples made from D. alata and D. rotundata D. rotundata genotypes were considered separately. Signifi-
genotypes (Fig. 3). TDr IGN 21 and D. rotundata were highly dis- cant correlations were also found between sensory stretchabil-
criminant and had the longest distance from all D. alata geno- ity and instrumental stringiness but varied according to
types. Through the TPA, it was also possible to classify the species combinations. However, this correlation was negative
pounded yam samples into three hierarchical classes, which clus- (combining the two species), significant for D. alata, but not
tered the genotypes into pounded yam of contrasting textural significant for D. rotundata. There was significant positive cor-
quality: not preferred quality (red color) the less preferred quality relation, between sensory moldability and instrumental stiff-
group (TDr1100180) and preferred quality group [TDr IGN ness (when both species were combined). The respective
21 (Igangan) (a landrace that was used as check, TDr1401419, correlations for the individual species, however, were not sig-
and TDr090067] (Fig. 3). Pounded yam samples from genotypes, nificant. Instrumental stiffness was positively correlated with
similar in textural quality, can be observed and compared to sensorial adhesiveness and hardness for both species individu-
genotypes of known quality (e.g., TDr IGN 21). Representative ally, but not in the combined analysis. There were a few addi-
TPA profiles for pounded yam (from both species) with preferred tional correlations that reached statistical significance but not
and non-preferred textural quality are presented in Fig. 4. in a consistent way for the two species (Table 5).
Correlation of instrumental TPA with QDA Chemical composition
The correlations between QDA and TPA for textural quality are There was variability in chemical composition of the yam geno-
presented in Table 5. Generally, there were good and positive cor- types (Table 6), which confirmed previously reported intraspecies
relations between instrumental cohesiveness with sensorial and interspecies variation in the chemical composition of
moldability and stretchability. In D. alata, there were correlations yam.15,24 Generally, there was an insignificant difference
between TPA and QDA parameters in terms of hardness, stick- (P > 0.05) in the mean value of starch (45.0% versus 44.9%), mois-
iness, cohesiveness, TPA cohesiveness and QDA stretchability, ture (6.1% versus 5.6%) and fat (0.3% versus 0.3%) contents of
while in D. rotundata there were correlations between TPA D. rotundata and D. alata species, respectively. However, there
and QDA in terms of cohesiveness and hardness and also were significant (P < 0.05) intraspecies differences for the sugar,
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Figure 3. Texture profile analysis of pounded yam from 12 yam genotypes and one landrace (TDr IGN 21 (Igangan)). (a) Principal component analysis
(PCA) of texture profile analysis of pounded yam from 12 yam genotypes and one landrace (TDr IGN 21 (Igangan)). (b) Discriminants of pounded yam
texture made from 13 genotypes of yam. (c) Hierarchical clusters of textural quality of pounded yam made from 12 yam genotypes and one landrace
(TDr IGN 21 (Igangan)).
moisture, ash, protein and crude fiber contents. Regarding the color of the pounded yam samples was observed, though
antinutritional contents, D. alata varieties had the highest mean the values were lower than in the raw yam tubers.
tannin content (1.23%), while D. rotundata genotypes had the
highest mean phytic acid (1.32%). Correlation between the chemical composition of yam
varieties and QDA of pounded yam samples
Color Table 8 shows the result of Pearson correlation analysis between
The activity of PPO enzyme over 100 s in fresh roots (oxidative the chemical composition of the yam tubers and sensory attri-
browning) (Fig. 5), for breeders' lines, in both species increased butes (QDA) of pounded yam samples made from them. In both
with time. Dioscorea rotundata genotypes had higher PPO activity the breeders' lines and the landraces, significant associations
than those of D. alata. PPO activity was also higher for the were observed between chemical compositions of raw tubers
D. rotundata landraces (except for Lasinrin), compared to the (ash, protein, fat, starch, moisture, tannin and phytate) and the
D. alata variety Ewura. sensory attributes of pounded yam.
The result of the instrumental color measurement for the yam
genotypes from breeders' lines is presented in Table 7. The color Prediction of sensory attributes of pounded yam through
of yam genotypes from D. alata was lighter, as shown by the biophysical traits
higher L* (lightness) and lower a* (red-green axis). In comparison, Predictions were based on the quality attributes of the yam land-
D. rotundata genotypes had a higher intense yellow color, shown races used for consumer studies. Linear multiple regressions were
by a higher value of b* (yellow-blue axis). A similar trend in the applied to predict the sensory attributes from the biophysical
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Figure 4. Representative texture profile analysis (TPA) of pounded yam from Dioscorea alata and Dioscorea rotundata varieties. (a) TPA of pounded yam
from D. alatawith poor textural quality. (b) TPA curve of pounded yam from D. alatawith good textural quality. (c) TPA of pounded yam from D. rotundata
with poor textural quality (d) TPA curve of pounded yam from D. rotundata with good textural quality.
parameters (Table 9). The best model was limited to two parame- had been described from participatory processing diagnosis as a
ters based on a high coefficient of determination (R2) already non-preferred variety because it produces very poor quality (not
obtained (> 0.99). Based on this predictive model, the smooth- moldable, not stretchable, lumpy) pounded yam.21
ness, adhesiveness/stickiness, moldability/cohesiveness, and Generally, in the consumer test, good quality pounded yam
stretchability (all with R2 = 1.00), and hardness (R2 = 0.99) of samples were described as ‘stretchable’, ‘soft’, ‘smooth’, ‘mold-
pounded yam samples can be predicted by varying pairs able’, ‘not sticky’, ‘white/creamy/yellow’ depending on the yam
of parameters. In addition, the texture analyzer parameters of flesh color, ‘sweet taste’ and ‘good aroma’. This agreed with the
adhesiveness (R2 = 1.00), cohesiveness (R2 = 1.00) and hardness food quality profile described by Otegbayo et al.12 The samples
(R2 = 1.00) can be used to predict the stickiness and moldability from Lasinrin, Gbongi-Kamilu and Awana fit into this group. How-
of pounded yam. In contrast, the color of the pounded yam sam- ever, it should be noted that previously in the participatory pro-
ples can be efficiently predicted by CIE indices (L*, a*, b*) of the cessing diagnosis,21 Gbongi-Kamilu was described as less
Hunter colorimeter (R2 = 1.00). preferred (when in the fresh state) in comparison with the other
varieties as a result of changes in flesh color during processing
and the ‘not too good’ quality of its pounded yam. But on storage
DISCUSSION (which was the state during which the consumer test was done),
Consumer acceptability test the quality of the pounded yam sample improved (as described
The most liked pounded yam samples were from Lasinrin, Awana by the consumers), this implied that storage must have led to
and Gbongi-Kamilu (Table 1) with sensory characteristics such as some changes in its biochemical composition which was reflected
‘smooth’, ‘moldable’, ‘good aroma’, ‘stretchable’, ‘sweet taste’, in its food quality attributes; this agrees with Otegbayo et al.25 on
‘soft’. Figure 1 describes the cluster groups of consumers and pounded yam made from stored yam tubers.
shows that more than half of the consumers interviewed disliked In summary, the results of the consumer test in both countries
the sample prepared from Ewura. Pounded yam from this variety Nigeria (southwest and southeast) and the Republic of Benin
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Table 5. Correlation between instrumental texture parameters and descriptive sensory evaluation parameters for pounded yam made from Dios-
corea rotundata and Dioscorea alata varieties
Sensory parametersa
Instrumental parameters
Stringiness (mm) Resilience (no unit)
Adhesiveness Cohesiveness Stiffness/
(g.mm) (no unit) hardness (g)
Dioscorea alata
Adhesiveness 0.76 −0.11 −0.68 −0.14 0.27
Moldability/cohesiveness 0.00 0.60 0.01 0.12 −0.13
Hardness/softness 0.78 0.09 0.63 0.25 0.30
Stretchability −0.03 0.70 0.09 0.51 0.70
Dioscorea rotundata
Adhesiveness −0.11 0.29 −0.54 −0.67 −0.36
Moldability/cohesiveness −0.25 0.81 0.12 −0.06 −0.29
Hardness/softness 0.11 −0.45 0.64 0.58 0.44
Stretchability −0.42 0.92 −0.35 −0.35 −0.36
Dioscorea alata and Dioscorea rotundata combined
Adhesiveness 0.34 0.01 −0.50 −0.32 −0.09
Moldability/cohesiveness −0.19 0.84 0.51 −0.39 0.21
Hardness/softness −0.32 −0.32 0.17 0.42 −0.14
Stretchability −0.30 0.91 0.26 −0.52 −0.02
Note: Values in bold typeface are significantly correlated.
point to the fact that the key quality traits in pounded yam are cohesive. This also points to the fact that the TPA can be used to
color and textural quality (stretchability, smoothness, moderate measure cohesiveness in pounded yam distinctively in place of
hardness, moldability and moderate stickiness). It should be a sensory panel.
noted that although the consumers rated sweetness and aroma There were significant correlations (P < 0.05) between other
as attributes of pounded yam, they unanimously reiterated that secondary instrumental parameters, chewiness, gumminess, cohe-
this was because the pounded yam was served to them without siveness, and sensory moldability and stretchability (Supporting
stew. About 91% of the respondents (Fig. S2) stated that they usu- Information Table S1 and Figure S3). However, these are not taken
ally eat the pounded yam with stew; hence the stew would have as key parameters since pounded yam consumers do not chew it,
masked off the taste and aroma. Therefore, taste and aroma were and the stew taken with it does not allow it to be gummy. From
not considered key quality attributes in pounded yam. the correlations between TPA and QDA it can be inferred that these
correlation results, TPA can be a medium-throughput phenotyping
Correlation between QDA and consumer testing method to characterize the textural quality of pounded yam in
Correlation between the QDA and consumer testing validates the place of QDA.
key quality traits – color and textural quality (smoothness, stretch-
ability, moldability, stickiness) – identified in pounded yam and to Color
be passed on to breeders. Results assessing color agree with the findings of Anosike and
Ayaebene26 that the PPO activity in D. rotundata is higher than
Instrumental texture profile analysis (TPA) that of D. alata but is in contrast to the findings of Otegbayo
There was no significant (P > 0.05) relationship between the et al.,27 which reported higher PPO activity in D. alata than that in
instrumental texture and sensory hardness, smoothness or sticki- D. rotundata. Variations in these authors' reports may result from
ness when all genotypes were analyzed together (confirming PCA differences in the botanical origin of the yam varieties used by
description). However, as a follow-up analysis, the yam genotypes the different authors. The QDA results in this study (Tables 2 and
were treated on species basis [because these yam species 3) also corroborated the results of PPO activity because pounded
(D. rotundata and D. alata) are uniquely different in their chemical yam samples from the D. alata varieties were described as creamy
compositions, starch properties and textural properties of their by the trained panelists, while pounded yam from D. rotundata
food products]. In D. alata, there were correlations between TPA was described as yellow. According to Omidiji and Okpuzor,20 only
and QDA parameters in terms of hardness, stickiness, cohesive- 40% of browning in D. rotundata is PPO activity related. Other pari-
ness, TPA cohesiveness and QDA stretchability, while in etal components such as moisture, protein, tannin, and phenolic
D. rotundata there were correlations between TPA and QDA profile can influence the color of yam products.19,26 Hence the
in terms of cohesiveness, hardness and also between TPA cohe- PPO activity of the yam tubers may be an index of browning rate
siveness and QDA stretchability. Correlations between TPA and and suggests a possible medium throughput phenotyping tool to
QDA have been reported previously.4 The correlation of cohesive- assess the browning rate of yam products.
ness and stretchability in pounded yam from both yam species Fromchromametermeasurement, the color of yamgenotypes from
implies that for pounded yam to be stretchable, it must be D. alatawas lighter, as shownby the higher L* (lightness) and lower a*
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Table 6. Chemical composition of Dioscorea rotundata and Dioscorea alata
Species/variety† Moisture (%) Ash (%) Protein (%) Fat (%) Starch (%) Sugar (%) Crude fiber (%) Tannin (%) Phytate (%)
Dioscorea rotundata‡
TDr1401419 5.23 ± 0.06d 2.31 ± 0.07d 4.51 ± 0.06e 0.30 ± 0.00a 48.89 ± 0.40b 4.67 ± 0.02b 1.54 ± 0.02c 0.18 ± 0.08d 1.21 ± 0.01d
TDr1100180 6.67 ± 0.06c 2.50 ± 0.04c 5.25 ± 0.04c 0.20 ± 0.00f 46.99 ± 0.59c 4.50 ± 0.02d 1.75 ± 0.03b 0.57 ± 0.10c 1.35 ± 0.01b
TDr1400359 4.41 ± 0.02e 1.59 ± 0.04f 6.19 ± 0.04a 0.33 ± 0.01a 35.30 ± 0.69f 4.62 ± 0.01c 1.54 ± 0.01c 1.75 ± 0.04a 1.24 ± 0.01c
TDr0900067 9.37 ± 0.08a 2.73 ± 0.01b 6.33 ± 0.06a 0.23 ± 0.01e 44.74 ± 0.62d 3.90 ± 0.01e 2.08 ± 0.06a 0.97 ± 0.11b 1.55 ± 0.01a
TDr100048 5.19 ± 0.11d 2.37 ± 0.07d 5.59 ± 0.07b 0.27 ± 0.00c 49.57 ± 0.66b 4.87 ± 0.02a 2.06 ± 0.05a 0.49 ± 0.10c 1.18 ± 0.01e
TDr1401593 5.27 ± 0.06d 2.85 ± 0.04a 6.18 ± 0.08a 0.32 ± 0.00b 52.42 ± 0.31a 4.69 ± 0.01b 1.61 ± 0.04c 0.47 ± 0.17c 1.21 ± 0.01d
TDr IGN 21 6.89 ± 0.11b 2.06 ± 0.04e 4.71 ± 0.09d 0.25 ± 0.00d 36.98 ± 0.60e 3.92 ± 0.02e 1.06 ± 0.05d 0.18 ± 0.09d 1.54 ± 0.01a
Mean 6.15b 2.34a 5.53a 0.27a 44.98a 4.45a 1.66a 0.66a 1.32b
Standard deviation 1.67 0.42 0.74 0.05 6.50 0.39 0.35 0.55 0.06
Dioscorea alata§
TDa1400301 5.82 ± 0.01c 2.70 ± 0.01d 5.60 ± 0.04c 0.32 ± 0.00a 41.95 ± 0.83c 4.58 ± 0.01e 1.84 ± 0.00e 1.53 ± 0.04a 1.25 ± 0.01a
TDa1100224 4.46 ± 0.05e 4.04 ± 0.07a 7.81 ± 0.04a 0.35 ± 0.00a 47.85 ± 0.37d 5.01 ± 0.01a 2.06 ± 0.00e 0.94 ± 0.05c 1.05 ± 0.00d
TDa1215201 5.87 ± 0.06c 3.01 ± 0.05c 5.71 ± 0.07c 0.3 ± 0.00a 45.25 ± 0.36b 4.59 ± 0.01e 1.85 ± 0.03e 1.27 ± 0.16b 1.24 ± 0.01a
TDa1100432 6.40 ± 0.02a 3.17 ± 0.06b 6.07 ± 0.04b 0.31 ± 0.00a 42.52 ± 0.81c 4.66 ± 0.01d 2.19 ± 0.02b 1.15 ± 0.04b 1.23 ± 0.01a
TDa1100201 6.09 ± 0.04b 3.12 ± 0.04cb 6.06 ± 0.11b 0.29 ± 0.00a 49.18 ± 0.30a 4.83 ± 0.01b 2.25 ± 0.04a 1.55 ± 0.13a 1.15 ± 0.00c
TDa1100316 4.92 ± 0.04d 3.20 ± 0.06b 6.02 ± 0.03b 0.33 ± 0.00a 42.61 ± 0.49c 4.75 ± 0.01c 1.99 ± 0.01d 0.98 ± 0.03c 1.18 ± 0.01b
Mean 5.59a 3.20b 6.21b 0.32a 44.89a 4.74b 2.03b 1.23b 1.18a
Standard deviation 0.74 0.45 0.81 0.02 3.06 0.16 0.17 0.26 0.08
Landraces¶
Lasinrin (TDr) 6.02 ± 0.25ab 1.73 ± 0.02b 5.57 ± 0.16bc 0.48 ± 0.05b 54.43 ± 0.25b 7.44 ± 0.12b 1.27 ± 0.0.01c 0.36 ± 0.00d 1.63 ± 0.01a
Kamilu (TDr) 5.04 ± 0.06bc 1.46 ± 0.05c 6.41 ± 0.15b 0.23 ± 0.01c 52.72 ± 0.11c 7.17 ± 0.08b 1.25 ± 0.01c 0.53 ± 0.02b 1.54 ± 0.04a
Awanah (TDr) 4.96 ± 0.10c 1.61 ± 0.04bc 4.78 ± 0.23c 0.41 ± 0.04b 55.38 ± 0.48a 7.28 ± 0.12b 2.17 ± 0.01b 0.40 ± 0.00c 1.00 ± 0.04b
Ewura (TDa) 6.28 ± 0.67a 2.37 ± 0.09a 7.50 ± 0.58a 0.71 ± 0.05a 53.11 ± 0.08c 8.53 ± 0.09a 2.29 ± 0.02a 1.98 ± 0.01a 0.80 ± 0.04c
Mean 5.57 1.79 6.07 0.46 53.91 7.60 1.75 0.83 1.24
Standard deviation 0.67 0.40 1.16 0.20 1.22 0.62 0.56 0.78 0.41
† Analysis done on dry weight basis.
‡ Means with the same letter in the same column in D. rotundata are not significant at 5%.
§ Means with the same letter in the same column in D. alata are not significant at 5%.
¶ Means with the same letter in the same column in landraces are not significant at 5%.
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(a)
0.025
0.02
0.015
0.01
0.005
0
0 sec 20 40 60 80 100
secs secs secs secs secs
Duration (secs)
D. rotundata D. alata
(b) (c)
Figure 5. Polyphenol oxidase (PPO) activity inDioscorea species. (a) PPO enzyme activity in rawDioscorea alata andDioscorea rotundata. (b) PPO enzyme
activity in raw yam landraces. (c) Summary of PPO enzyme activity in raw Dioscorea species.
(red-green axis). In comparison, D. rotundata genotypes had a higher Correlation between the chemical composition of yam
intense yellow color, shown by a higher value of b* (yellow-blue axis). varieties and QDA of pounded yam samples
A similar trend in the color of the pounded yam samples was Significant associations were observed between the sensory attri-
observed, though the values were lower than in the raw yam tubers. butes of pounded yam and chemical composition as estimated by
This may be due to thermal degradation of originally colorless com- NIRS: ash, protein, fat, starch, dry matter, tannin and phytate.
plex phenolics to colored phenols28 or other reactions, such as Mail- Other authors7,15,30,31 have also shown that root or tuber content
lard reactions during the cooking of the yam. Chromameter of drymatter, protein and sugars can be determinants of quality in
measurement could be used as a high throughput method to evalu- root and tuber crops. This observation implies that the yam
ate the color of pounded yam, as a criterion of consumer acceptance. tuber's parietal composition can influence the pounded yam's
An image analysis method has also been developed29 to eval- textural quality. The correlation of the dry matter content of the
uate color in fresh yam tubers. Its advantage is the ability to cap- yam tubers with all the sensory attributes of the pounded yam
ture color in heterogeneous (not smooth) surfaces; hence this except the adhesiveness further reinforces previous reports7,30,32
will circumvent having to carry out many measurements at dif- that dry matter and starch are essential determinants of textural
ferent points as done with the chromameter. The standard oper- quality in pounded yam.
ating procedure for its potential use for high throughput color Correlations between the protein content of the tubers and the
estimation in pounded yam is being worked on in the RTBfoods smoothness, adhesiveness, moldability and stretchability of
project. pounded yam may be a result of starch granule-associated
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Absorbance
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Table 7. Instrumental color measurement of Dioscorea species
Raw tuber at 0 min£ Raw tuber after 10 min¥ Pounded yam
L* a* b* L* a* b* L* a* b*
Dioscorea rotundata†
TDr1401419 86.16 ± 3.21a −2.21 ± 0.35cb 18.80 ± 0.17c 83.23 ± 0.54ab −1.81 ± 0.30b 18.59 ± 0.88c 76.26 ± 0.69a −1.84 ± 0.32c 16.09 ± 0.43d
TDr1100180 83.49 ± 0.45ab −5.09 ± 0.20e 29.57 ± 0.44b 82.20 ± 0.38b −5.20 ± 0.06ed 30.00 ± 0.33b 67.73 ± 1.57fe −4.85 ± 0.15e 25.98 ± 0.85b
TDr1400359 81.51 ± 0.15bc −1.51 ± 0.32b 15.82 ± 0.13d 79.39 ± 0.11cd −0.96 ± 0.00b 16.41 ± 0.01c 73.73 ± 0.11b −0.80 ± 0.04b 12.65 ± 0.02e
TDr0900067 80.14 ± 0.48c 0.93 ± 0.07a 13.98 ± 1.08d 77.80 ± 0.07d 0.69 ± 0.69a 17.36 ± 1.87c 66.89 ± 0.35f 1.04 ± 0.03a 12.02 ± 0.04e
TDr100048 84.61 ± 0.35ab −3.27 ± 0.06d 19.57 ± 0.56c 84.89 ± 0.59a −3.14 ± 0.17c 18.98 ± 1.22c 69.41 ± 0.04d −3.48 ± 0.22d 18.37 ± 0.61c
TDr1401593 79.66 ± 0.11c −2.83 ± 0.90dc 31.68 ± 0.81ab 81.10 ± 2.15bc −4.53 ± 0.67d 33.29 ± 2.43a 68.66 ± 0.06ed −3.48 ± 0.00d 27.74 ± 0.27a
TD IGN 21 83.70 ± 0.39ab −6.07 ± 0.06f 32.25 ± 1.97a 82.50 ± 0.00b −5.64 ± 0.00e 33.46 ± 0.00a 71.93 ± 0.01c −5.73 ± 0.26f 28.06 ± 0.62a
Mean 82.75 −2.86 23.09 81.59 −2.94 24.01 70.66 −2.73 20.13
Standard deviation 2.40 2.31 7.81 2.39 2.36 7.83 3.43 2.36 7.03
Dioscorea alata‡
TDa1100316 86.50 ± 0.27a −2.03 ± 0.01d 17.59 ± 0.82cb 84.74 ± 0.06a −2.04 ± 0.03c 17.43 ± 0.59c 83.78 ± 1.77a −2.59 ± 0.04e 17.76 ± 0.31a
TDa1100201 84.13 ± 0.04c −1.76 ± 0.00c 17.51 ± 0.08cb 84.64 ± 0.09a −1.89 ± 0.01cb 18.24 ± 0.03b 71.69 ± 0.93c −2.54 ± 0.06e 15.18 ± 0.18c
TDa1100432 83.1 ± 0.05d −1.27 ± 0.09b 18.06 ± 0.04b 83.99 ± 0.10b −1.57 ± 0.01cb 17.82 ± 0.01cb 85.70 ± 0.00a −1.72 ± 0.01d 16.08 ± 0.02b
TDa1100224 81.375 ± 0.02c −0.78 ± 0.06a 19.59 ± 0.21a 81.14 ± 0.16c −0.16 ± 0.86a 20.22 ± 0.04a 70.09 ± 0.11c −1.19 ± 0.02c 14.95 ± 0.33c
TDa1415201 84.93 ± 0.01b −1.22 ± 0.06b 19.33 ± 0.23a 84.22 ± 0.23b −0.98 ± 0.20ba 18.48 ± 0.23b 65.18 ± 0.08d −0.86 ± 0.01b 14.76 ± 0.14c
TDa1400301 85.395 ± 0.46b −1.29 ± 0.04b 16.6 ± 0.69c 84.83 ± 0.01a −1.14 ± 0.12cb 15.47 ± 0.18d 75.85 ± 0.09b 1.27 ± 0.06a 11.27 ± 0.04d
Mean 84.29 −1.39 18.11 83.92 −1.3 17.94 75.38 −1.27 15.00
Standard deviation 1.81 0.44 1.15 1.40 0.69 1.55 8.04 1.43 2.13
Landraces§
Lasinrin (TDr) 82.43 ± 0.56c −5.05 ± 0.12d 28.93 ± 0.39a 79.52 ± 0.14c −4.86 ± 0.02c 27.14 ± 0.12b 66.17 ± 1.14ba −5.43 ± 0.13d 26.55 ± 0.43a
Kamilu (TDr) 81.60 ± 0.20d −4.72 ± 0.15c 29.06 ± 0.86a 79.98 ± 0.99c −5.15 ± 0.06d 28.24 ± 0.22a 62.47 ± 1.85c −0.49 ± 0.07b 10.51 ± 0.10c
Awanah TDr) 83.21 ± 0.31b −2.54 ± 0.05b 17.84 ± 0.22b 82.39 ± 0.32b −2.27 ± 0.15b 17.82 ± 0.02c 67.61 ± 0.34a −1.68 ± 0.06c 14.29 ± 0.10b
Ewura (TDa) 84.06 ± 0.48a −0.34 ± 0.17a 14.65 ± 0.51c 83.89 ± 0.40a −0.27 ± 0.17a 14.32 ± 0.62d 65.34 ± 0.49b 2.43 ± 0.12a 10.68 ± 0.09c
Mean 82.82 −3.16 22.62 81.45 −3.14 21.88 65.40 −1.29 15.51
Standard deviation 1.06 2.18 7.48 2.06 2.31 6.87 2.16 3.25 7.57
† Means with the same letter in the same column in D.rotundata are not significant at 0.05 level.
‡ Means with the same letter in the same column in D. alata are not significant at 0.05.
§ Means with the same letter in the same column in landraces are not significant at 0.05.
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Table 8. Correlation between chemical composition of yam varieties and quantitative descriptive analysis (QDA) of pounded yam samples
Smoothness Adhesiveness Moldability Stretchability Hardness Color
Breeders' lines
Moisture −0.34 0.12 0.48* 0.48* −0.54** 0.21
Ash 0.74** −0.13 −0.69** −0.76** 0.42* −0.46*
Fat 0.48* −0.03 −0.68** −0.59* 0.54** −0.46*
Protein 0.62** −0.15 −0.61** −0.64** 0.37 −0.28
Sugar 0.55** −0.22 −0.55** −0.67** 0.45* −0.36
Starch 0.18 −0.22 −0.14 −0.29 0.01 −0.05
Amylose −0.19 −0.08 0.36 0.21 −0.11 0.25
Crude fiber 0.62** −0.20 −0.47* −0.64** 0.10 −0.51**
Tannin 0.54** 0.10 −0.57** −0.67** 0.08 −0.57**
Phytate −0.58** 0.18 0.60** 0.69** −0.48* 0.44*
Landraces
Moisture −0.60 −0.48 −0.46 −0.30 −0.36 0.76*
Ash −0.94** −0.34 −0.85** −0.53 −0.42 0.50
Fat −0.82* −0.14 −0.67 −0.25 −0.63 0.38
Protein −0.78* −0.78* −0.90** −0.94** 0.30 0.74*
Sugar −0.95** −0.38 −0.88** −0.61 −0.37 0.53
Starch 0.44 0.80* 0.63 0.86** −0.55 −0.69
Amylose 0.53 −0.39 0.46 0.18 0.49 0.44
Dry matter raw tuber −0.95** −0.61 −0.98** −0.89** −0.01 0.63
Crude fiber −0.68 0.34 −0.53 −0.12 −0.70 −0.27
Tannin −0.99** −0.47 −0.97** −0.76* −0.23 0.54
Phytate 0.76* −0.23 0.64 0.26 0.64 0.18
*Correlation is significant at the 0.05 level (two-tailed).
** Correlation is significant at the 0.01 level (two-tailed).
proteins (SGAPs), which occur on the surface of starch granules A novel correlation observed in this study is that between the
and have been reported to influence starch functionality by ash content of the tubers and the moldability of the derived
affecting its pasting properties through the reduction in its viscos- pounded yam. It was observed that the more ash content, the
ity, mechanical fragmentation and also conferring rigidity to the less the moldability of the pounded yam [R2 = 0.53 (Fig. S3c)].
swollen granules, thus affecting the textural quality of the food Thus, ash can potentially be an interesting rapid test for breed-
product.33,34 In addition, proteins in starch matrices have been ing. In addition, this observation of correlation of ash and mold-
reported35,36 to influence the textural quality of foods by interact- ability can be linked to the role of pectin in binding with divalent
ing C-2 and C-3 hydroxyl groups of glucose units through cations (from ash) to form a gel-like structure, which influences
hydrogen-bonding and act as a barrier preventing chain forma- the texture of food by increasing its firmness and rigidity,22,39
tion between amylose and amylopectin helices, thus affecting therefore, the more divalent cations, the more the pectin is
its starch retrogradation and its final viscosity; which affects the complexed.
textural quality of the food product. The significant correlation of crude fiber with the smoothness of
Fat may influence the textural quality of pounded yam due to the pounded yam was expected, as this can be as a result of solu-
the formation of amylose–lipid complexes, which alters the func- ble and insoluble fiber in the yam tubers, which can affect the
tionality of starches and hence its cooking properties.37,38 fibrousness of the pounded yam.25
Table 9. Predictive models of sensory attributes from chemical and biophysical parameters based on data from landraces
Sensory attributes Explicative variables Regression equation/predictive models R2 P-Value
Smoothness Starch (lab) and tannin (lab) 24.62–0.24 × Starch-4.31 × Tannin 1.0 0.007
Adhesiveness/stickiness Stickiness (TVT) and amylose 4.45–1.85E-03 × Stickiness-0.14 × Amylose 1.0 0.020
Modability/cohesiveness Stiffness/hardness (TVT) and −4.05 + 1.05E-03 × Stiffness/Hardness + 1.0 0.006
cohesiveness (TVT) 16.73 × Cohesiveness
Stretchability Adhesiveness (TVT) and protein 20.10 + 4.60E-04 × Adhesiveness-2.54 × Protein 1.0 0.011
Hardness Starch (lab) and tannin (lab) 54.47–0.88 × Starch-1.01 × Tannin 1.0 0.029
Color a010_raw and L_py 139.67–12.90 × a010_raw-2.08 × L_py 1.0 0.066
Abbreviation: TVT, texture analyzer parameter; a010_raw, red-green index (CIE) of raw tuber 10 min after cutting; L_py, lightness index (CIE) of
pounded yam.
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Figure 6. Sensory food product quality (FPQ) assay for pounded yam: Clustering of food quality traits of TDr1401220 with Meccakusa (landrace).
The correlation between tannin and phytate may result from The main objective of this study was to identify the key bio-
forming soluble and insoluble complexes with divalent cations chemical traits in yam tubers that can predict the key food quality
and proteins. These complexes may influence the textural attri- attributes of pounded yam and determine those that can be used
butes of the food product.36 Phosphorous accounts for about in medium and high throughput methods by breeders. The bio-
20–21% of phytic acid in root and tuber crops; it occurs in the chemical traits being recommended in this study that can fulfill
form of phosphorous.40 Phosphorous in the form of phosphor- these objectives are dry matter, starch, amylose, and ash.
mono esters has been implicated in influencing the textural qual-
ity of pounded yam through its effect on starch functionality, such Breeders' perspective
as increasing starch swelling and viscosity, which in turn influence This study demonstrates some key tools to predict the consumer-
its textural quality.41 demanded quality attributes of pounded yam from instrumental
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www.soci.org B Otegbayo et al.
TPA including stickiness/adhesiveness from the starch and amy-
lose content of the tubers. Color can be objectively measured by SUPPORTING INFORMATION
means of a colorimeter and textural attributes such as adhesive- Supporting informationmay be found in the online version of this
ness and moldability of the pounded yam can be measured by article.
texturometer, the added advantage of these methods being
throughput will also reduce the screening and selection time for
breeding lines. These throughput methods are now adopted in
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