Composition and functional properties of unprocessed and locally processed seeds from three underutilized food sources in Nigeria

Physicochemical Characterization of Detarium microcarpum Seeds from Northern Benin

The objective of this work is to determine the physicochemical characteristics of the Detarium microcarpum seeds from North Benin, specially the proximate composition, colour, minerals, and antinutritional factors using standard analytical methods. The results show that the contents of moisture, protein, total sugars, lipid, crude fiber, and ash ranged, respectively, from 10.85 to 14.69%, from 13.54 to 17.82%, from 19.69 to 32.04%, from 8.68 to 11.90%, from 19.78 to 34.24%, and from 1.5 to 3.49%. The luminance (l∗), red saturation (a∗), and yellow saturation (b∗) have, respectively, ranged from 60.45 to 67.64, from 5.44 to 8.86, and from 8.24 to 9.28. Seeds contain interesting contents of potassium, calcium, magnesium, manganese, sodium, and iron; they have, respectively, varied from 6141.88 to 12305.16 mg/kg, from 1254.47 to 2168.62 mg/kg, from 1298.87 to 2533.06 mg/kg, from 75.18 to 307.23 mg/kg, from 53.52 to 136.19 mg/kg, and from 28.46 to 181.42 mg/kg. The investigation of antinutritional factors indicates the presence of oxalates, phytates, total phenolic compounds, and saponins with contents that have varied, respectively, from 1.01 to 2.36%, from 0.37 to 0.87%, from 3.13 to 7.61%, and from 1.35 to 4.59%. On average, the physicochemical characteristics of the Sudanian and Sudano-Guinean zones are similar, except for total sugar content.

African plant foods rich in non-starch polysaccharides reduce postprandial blood glucose and insulin concentrations in healthy human subjects

The effects of two vegetable flours, prepared from the African plants Detarium senegalense Gmelin, a legume, and Cissus rotundifolia, a shrub, on postprandial blood glucose and insulin concentrations in human subjects, were investigated. Chemical analysis indicated that these flours contained significant amounts of NSP. The detarium in particular was found to be a rich source of water-soluble NSP (SNSP). The flours were incorporated into two types of breakfast meal, a stew meal and a wheat bread meal, containing 50 g and 70 g available carbohydrate respectively. Both meals also contained 10–12g NSP, the major fraction of which was SNSP. Control and fibre-rich meals were consumed on separate days in randomized order by two different groups of subjects (n 5, stew meals; n 10, bread meals). Venous blood samples were taken at fasting (0 min) and postprandially at 30 min intervals for 2·5 h and the plasma analysed for glucose and insulin. Compared with the controls, detarium and cissus meals elicited significant reductions (P < 0·006) in plasma glucose levels at most postprandial time points and for area-under-the-curve (AUC) values (AUC reductions 38–62%). Significant reductions (P < 0·002) in plasma insulin levels at various postprandial time points and for AUC values were also seen after detarium and cissus breads (AUC reductions 43 and 36% respectively), but not after the fibre-rich stew meals. SNSP and starch are possibly the main, but not the only, components responsible for the glucose- and insulin-lowering effects of cissus flour. The main SNSP fraction of detarium, identified as a high-molecular-weight xyloglucan, is likely to be a primary factor in determining the physiological activity of detarium flour.

Metabolic and hormonal effects of five common African diets eaten as mixed meals: the Cameroon Study

OBJECTIVE

To evaluate glycaemic and insulinaemic index and in vitro digestibility of the five most common Cameroonian mixed meals consisting of rice+tomato soup (diet A), bean stew+plantains (B), foofoo corn+ndolé (C), yams+groundnut soup (D), and koki beans+cassava (E).

SUBJECTS

Ten healthy non-obese volunteers, aged 19-31 y, with no family history of diabetes or hypertension.

INTERVENTIONS

A 75 g oral glucose tolerance test followed by the eating of the test diets with carbohydrate content standardized to 75 g every 4 days with blood samples taken at 0, 15, 30, 60, 120 and 180 min. In vitro digestion of each diet according to Brand's protocol.

MAIN OUTCOME MEASURES

Plasma glucose, cholesterol, triglyceride, insulin and C-peptide, with calculation of glycaemic and insulinaemic index defined as the area under the glucose and insulin response curve after consumption of a test food divided by the area under the curve after consumption of a control food containing the same amount of carbohydrate, and digestibility index.

RESULTS

Glycaemic index (GI) varied from 34.1 (diet C) to 52.0% (diet E) with no statistical difference between the diets, and insulinaemic index varied significantly from 40.2% (C) to 70.9% (A) (P=0.03). The digestibility index varied from 18.9 (C) to 60.8% (A) (P<0.0001), and did not correlate with glycaemic or insulinaemic indices. However, carbohydrate content correlated with GI (r=0.83; P=0.04), digestibility index (r=-0.70; P<0.01), and insulinaemic index (r=0.91; P<0.01). Plasma C-peptide and plasma lipids showed little difference over 180 min following the ingestion of each meal.

CONCLUSIONS

Glycaemic index of these African mixed meals are relatively low and might not be predicted by in vitro digestibility index.