Biochemical and textural changes in trifoliate yam Dioscorea dumetorum tubers after harvest

• Published in: Food chemistry Vol. 79; no. 1; pp. 27 - 40
• Main Authors: Sefa-Dedeh, Samuel, Ohene Afoakwa, Emmanuel
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.10.2002; Elsevier
• Subjects: Biochemical changes; Biological and medical sciences; Chemical changes; Cooked; Dioscorea dumetorum; Food industries; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; Physical changes; Post-harvest storage; Raw; Textural changes; Physical changes; Cooked; Dioscorea dumetorum; Textural changes; Post-harvest storage; Raw; Chemical changes; Biochemical changes; Monocotyledones; Yam; Uncooked food; Postharvest; Texture; Dioscoreaceae; Warehousing; Quality; Angiospermae; Dioscorea; Tuber; Spermatophyta; Herbaceous plant; Cooked food
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/S0308-8146(02)00172-3

Biochemical and textural changes were investigated in trifoliate yam Dioscorea dumetorum tubers, after harvest, in an attempt to study the chemical and physical changes associated with the raw and cooked tubers and how these relate to the hardening phenomenon of the tubers after harvest. A 2×2×3×4 factorial experiment, with cultivar, storage condition, treatment and storage time as their respective variables, was done. Samples were analysed for moisture, starch, reducing sugars, alcohol-soluble sugars, acid and neutral detergent fibre, cellulose, hemicellulose and lignin. The Warner–Bratzler test cell was used in a TA.XT2 Texture Analyser to measure the hardness of cooked tubers. The moisture and starch contents of the tubers decreased from 77.8 to 70.4% and 70.5 to 66.5 g/100g, respectively in a period of 72 h of storage, suggesting rapid dehydration after harvest and breakdown of starch. All the other chemical indices increased with storage time. These changes were influenced by the storage temperature and the treatment given to the tubers prior to storage. In general, samples stored at 4 °C showed smaller changes in the chemical indices than those at 28 °C, suggesting a temperature-dependence of the changes. Both cultivars of yam showed increase in hardness with storage time. A high correlation ( r=0.9503–0.9913) was noted between the texture and the chemical indices of the white cultivars. Storage of the trifoliate yam, Dioscorea dumetorum, immediately after harvest, leads to reduction in moisture and starch contents and increase in sugars and structural polysaccharides. Low temperature storage may reduce the hardening phenomenon. A mechanism for the hardening phenomenon has been proposed.