Native starches were extracted from 21 cultivars of four yam species representative of the yam population of Ivory Coast. They were first characterized for their proximate composition, starch physico-chemical properties (amylose content, particle size distribution, crystallinity, thermal properties and intrinsic viscosity). Some functional properties (swelling, solubility and pasting behaviour and paste clarity) were then determined. Analysis of variance and principal component analysis showed that three homogenous groups could be distinguished, mainly based on starch physico-chemical properties. The first group contained all yam starches of the D alata and the D cayenensis-rotundata complex species. It was characterized by a large diameter grain (approximately 25 µm), a high amylose content (around 25% db), a high intrinsic viscosity (mean of 190 cm 3 g −1 ), and a high apparent viscosity and clarity of the paste. The second group contained the D esculenta varieties, characterized by a small granule size (diameter 6 µm), a low intrinsic viscosity (121 cm 3 g −1 ), a high gelatinization enthalpy change (19 J g −1 ) and a low paste viscosity. The D dumetorum sample differed from the D esculenta group by having a pure A-type crystalline form and an opaque paste. A multiple regression showed that the volume fraction of the dispersed phase and native granule size (or amylose content) could account for close to 80% of the variability of paste apparent viscosity. Gel clarity appeared mainly linked to granule size, small granules from D dumetorum and D esculenta giving the most opaque gels.

Starches from ten yam (Dioscorea) species were compared with those of maize, wheat, potato and cassava, and characterized by high-performance size-exclusion chromatography coupled with multiangle laser light scattering. Treatment with 95% (v/v) dimethylsulphoxide and microwave heating in a high-pressure vessel led to complete dissolution of the starch samples. For yam starches, M w were between 1.88 × 10 8 and 3.27 × 10 8 g mol −1 and R G were between 258 and 396 nm. The hydrodynamic coefficients of amylopectins were between 0.36 and 0.44, indicating that those of maizes and esculenta 5 and dumetorum yam species had particularly highly branched structures. Multidimensional analysis of the macromolecular characteristics of yam starches indicated three classes: dumetorum cultivar (Dioscorea dumetorum), esculenta 5 cultivar (Dioscorea esculenta) and the other eight yam starches, including cultivars of Dioscorea alata and Dioscorea cayenensis-rotundata species. Some yam starches were also leached at 90 • C. The macromolecular characteristics of the leached fractions confirmed the previous typology.

There is currently an increased global interest in the published glycaemic index (GI) and glycaemic load (GL) values of foods. However, data on the GI and GL values of different varieties of foods within Côte d’Ivoire are very limited. The study therefore aimed at finding the GI and GL of the main food staples in Côte d’Ivoire. Following the International Standard Organisation’s protocol (ISO/FDI 26642:2010), a selection of five staple foodstuffs were tested for their GI and GL. Fasted healthy subjects were given 50 g of available carbohydrate servings of a glucose reference, which was tested twice, and test foods which were tested once, on separate occasions. Excepted attieke (GI 63), the majority of foods tested have a high GI (GI > 70). Attieke (agbodjama) had a high GL (GL 29) while placali (GL 17) and maize meal stiff porridge (GL 16) had medium GLs. The GLs of pounded cassava-plantain and pounded yam are 26 and 22. Consumption of attieke could minimize postprandial blood glucose spikes, in spite of high GL and potentially have benefit in the management and prevention of some chronic diseases.

Total starch (TS) and resistant starch (RS) contents in pasty edible product of mealy and hard cooking tubers of three yam varieties and four cassava varieties were determined to evaluate their contribution in their cooking quality. TS and RS contents appeared as the main components in determining yam cooking quality. Mealy cooking yam varieties were characterized by a significant higher TS content (75.2 ± 7.7 g/100 g d.m.) and lower RS content (13.8 ± 3.4 g/100 g d.m.) than hard cooking yam varieties, which, in contrast, contained less TS (61.7 ± 12.1 g/100 g d.m.) and particularly high RS (21.8 ± 9.9 g/100 g d.m.), possibly as a consequence of the prevalence of large granules (35-40 μm) observed by light microscope. Conversely, TS and RS contents appeared not determinant on the cooking quality of cassava. Moreover, higher amylose contents were associated with substantially elevated percentages of RS in yam and cassava, and high RS content in samples modulates their pasting properties by reducing the peak viscosity and the breakdown and requiring higher temperature and longer time to the peak.

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The starches of the wild yam species Dioscorea praehensilis, D. hirtifl ora, D. burkilliana, D. togoensis, D. dumetorum and D. bulbifera (tuber and bulbil) were isolated, and their paste viscosity and clarity, iodine binding and syneresis were investigated. Copyright

Yam wholesalers who practice speculative storage sometimes suffer significant losses the level of which has been little studied. Thus, this work was carried out to study the practices and deterioration factors of 'Kponan' yam during storage. To achieve this, 51 yam wholesalers in 4 communes of Abidjan (Abobo, Adjamé, Yopougon and Treichville) were interviewed using a survey form. The data showed that according to storage practices, yams are preferentially grouped by variety (100%) and old yams separately (88.2%). Wholesalers (94.1%) regulate the storage temperature either by fans (23.5%), by air openings in the wall (25.5%), or by fans and air openings in the wall (45.1%). Decay was the most common damage among all wholesalers (100%), followed by weight loss (52.9%), mold (35.3%), injury (29.4%), cracking (23.5%), and sprouting (17.6%). Heat was the main cause of yam damage, followed by moisture (82.3%), animals (31.4%), field storage conditions (17.6%), chemical use during cultivation (17.6%) and sprouting (17.6%). This study shows that the storage and temperature control techniques employed by wholesalers are far from mitigating the heat that is the main cause of damage to 'Kponan' yam (Dioscorea Cayenenis-rotundata) during storage.