Thermal Properties and Dynamic Rheological Characterization of Dioscorea Starch Gels.

Yam (Dioscorea. sp.) is an edible starchy tuber with potential for being a commercial source of starch for industrial purposes, but yam starch is underutilized. The dynamic oscillatory and thermal properties of yam starches from sixteen varieties each of Dioscorea. rotundata, Dioscora. alata, Dioscorea. bulbifera and one variety of Dioscorea. dumetorum from Nigeria were studied to determine their potential for industrial utilization. The storage modulus, loss modulus, damping factor and complex viscosity as a function of frequency (ω) of the dioscorea gels, as well as the onset temperature (To), peak gelatinization temperature (Tp), end of gelatinization (TC), and gelatinization enthalpy of the starches were determined by standard procedures. Results showed that all the dioscorea starches showed a typical elastic behavior with the magnitude of G' greater than G″ while tan δ < 1 in all varieties. Thus, the starch gels were more elastic than viscous. All the starch gels exhibited shear thinning characteristics and showed frequency (ω) independence characteristics of weak gels. D. rotundata varieties had the lowest ∆Hgel, while D. bulbifera varieties had the highest. The diversity of the visco-elastic and thermal properties of the yam starch gels from different varieties and species can be an advantage in their utilization in both food and non-food industries.

Review of instrumental texture measurements as phenotypic tool to assess textural diversity of root, tuber and banana food products.

Roots, tubers and bananas (RTBs) contribute immensely to food security and livelihoods in sub-Saharan Africa, Asia and Latin America. The adoption of RTB genotypes in these regions relies on the interplay among agronomic traits, ease of processing and consumer preference. In breeding RTBs, until recently little attention was accorded key textural traits preferred by consumers. Moreover, a lack of standard, discriminant, repeatable protocols that can be used to measure the textural traits deter linkages between breeding better RTB genotypes and end user/consumer preferences. RTB products texture - that is, behaviour of RTB food products under unique deformations, such as disintegration and the flow of a food under force - is a critical component of these preferences. The preferences consumers have for certain product texture can be evaluated from expert sensory panel and consumer surveys, which are useful tools in setting thresholds for textural traits, and inform breeders on what to improve in the quality of RTBs. Textural characterization of RTBs under standard operating procedures (SOPs) is important in ensuring the standardization of texture measurement conditions, predictability of textural quality of RTBs, and ultimately definition of RTB food product profiles. This paper reviews current SOPs for the textural characterization of RTBs, including their various associated methods, parameters, challenges and merits. Case studies of texture characterized during development of SOPs and evaluation of texture of RTB populations are discussed, together with insights into key textural attributes and correlations between instrumental, sensory and consumer assessment of texture unique to various RTB food products. Hardness was considered a universal key textural attribute to discriminate RTBs. The review should provide adequate insight into texture of RTB food products and critical factors in their measurement. It aims to promote inclusion of texture in breeding pipelines by investigating which textural traits are prioritized by consumers, particularly since the inclusion of textural traits has recently gained prominence by breeders in improving RTBs. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Food quality profile of pounded yam and implications for yam breeding.

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-throughput methods 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 sensory quantitative descriptive analysis (QDA) validated that preferred priority quality traits in pounded yam were related to textural quality (smooth, stretchable, moldable, slightly sticky and moderately hard) and color (white, cream or light yellow). There were significant correlations between sensory textural quality attributes cohesiveness/moldability, hardness, and adhesiveness/stickiness, with textural quality measurements from instrumental texture profile analysis (TPA). Color measurement parameters (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.

End-user preferences for pounded yam and implications for food product profile development.

Pounded yam is a popular food in Nigeria. This study reports end-user preferences for pounded yam and implications for trait evaluation by breeding programme. The study was carried out in two pounded yam-consuming regions in Nigeria: south-east and south-west. Multistage sampling technique was used to collect information from users along food chain. This involved market, individual, key informant interviews and focus group discussions. Responses of participants were used to develop product profile of pounded yam from raw material (yam) to final product. Key user-preferred quality traits for pounded yam in both regions were colour and textural quality followed by taste and aroma which are lesser attributes. There were regional differences in ranking of these quality attributes but no gender difference. This information will be useful in determining food quality indicators that can be used to select breeding lines for preferred quality traits in pounded yam.