Folake O. Henshaw

Effect of variety and processing method on functional properties of traditional sweet potato flour (“elubo”) and sensory acceptability of cooked paste (“amala”)

“Amala” is a generic term in Nigeria, used to describe a thick paste prepared by stirring flour (“elubo”) from yam, cassava or unripe plantain, in hot water, to form a smooth consistency. In order to overcome its high perishability and increase the utilization of sweet potato roots, three varieties of sweet potato roots were processed into flour using two methods. The interactive effect of variety and the processing method had a significant effect (P < 0.05) on all the functional properties of the flour except yellowness, setback viscosity, and peak time. Acceptable sweet potato “amala” with average sensory acceptability score of 7.5 were obtained from yellow-fleshed varieties irrespective of the processing method. Flour that produced acceptable “amala” were characterized by lower values of protein (2.20–3.94%), fiber (1.30–1.65%), total sugar (12.41–38.83 μg/mg), water absorption capacity (168–215 g/100 g), water solubility (8.29–14.65%), swelling power (0.52–0.82 g/g), and higher peak time (6.9–8.7 min).

Optimization of processing conditions for vacuum frying of high quality fried plantain chips using response surface methodology (RSM)

Optimization of processing conditions (temperature 122 to 136°C, vacuum pressure 9.91 to 19.91 cmHg, and frying time 3 to 9 min) during vacuum frying of plantain chips was investigated using a Box-Behnken experimental design with response surface methodology (RSM). Models for various responses were developed and optimized frying conditions using numerical solutions were established. Optimized vacuum fried samples were compared with atmospheric fried samples based on the concept of equivalent thermal driving force (ETDF). Frying parameters had significant (p<0.05) effects on the moisture content, texture, and color with a coefficient of determination (R2) for quadratic model responses varying between 0.53 and 0.99. Optimum vacuum frying conditions for plantain chips were a frying temperature of 133°C, vacuum pressure of 9.91 cmHg, and frying time of 6 min based on desirability concepts. Vacuum fried plantain chips had more acceptable sensory properties, based on ETDF values, than atmospheric fried samples.

Functional characterization of flour of selected cowpea (Vigna unguiculata) varieties: canonical discriminant analysis

Abstract Characterization of 28 varieties of cowpea flour, based on Brabender pasting properties of flour slurry (12% w/w flour: water), was achieved by canonical discriminant analysis. Pasting viscosities at various points on the amyiogram, pasting temperature and paste viscosity ratios were obtained for each variety of flour. Significant varietal influence on pasting properties was indicated by ANOVA ( P

Quality attributes of sweet potato flour as influenced by variety, pretreatment and drying method.

Abstract The effect of pretreatment methods (soaking in water, potassium metabisulphite solution, and blanching) and drying methods (sun and oven) on some quality attributes of flour from ten varieties of sweet potato roots were investigated. The quality attributes determined were chemical composition and functional properties. Data obtained were subjected to descriptive statistics, multivariate analysis of variance, and Pearsons correlation. The range of values for properties of sweet potato flour were: moisture (8.06–12.86 ± 1.13%), starch (55.76–83.65 ± 6.82%), amylose (10.06–21.26 ± 3.92%), total sugar (22.39–125.46 ± 24.68 μg/mg), water absorption capacity (140–280 ± 26), water solubility (6.89–26.18 ± 3.80), swelling power (1.66–5.00 ± 0.50), peak viscosity (24.50–260.92 ± 52.61 RVU), trough (7.08–145.83 ± 34.48 RVU), breakdown viscosity (11.00–125.33 RVU), final viscosity (10.21–225.50 ± 60.55 RVU), setback viscosity (3.04–92.21 RVU), peak time (6.07–9.06 min) and pasting temperature (69.8–81.3°C). Variety had a significant (P < 0.001) effect on all the attributes of sweet potato flour. Pretreatment did not significantly (P > 0.05) affect moisture, fat and lightness (L*). Drying method did not significantly (P > 0.05) affect fiber and L*. The interactive effect of variety, pretreatment and drying method had a significant (P < 0.001) effect on all the attributes except fat and fiber. Total sugar correlated significantly (P < 0.01) with water solubility (r = 0.88) of the flour samples. Variety was a dominant factor influencing attributes of sweet potato flour and so should be targeted at specific end uses.

Multivariate analysis of quality attributes of sweetpotato flour

Multivariate methods such as factor analysis (FA), cluster analysis and discriminant function analysis (DFA) were employed in this study to evaluate important parameters for characterization and quality control analysis of sweetpotato flour. Eighty samples of sweetpotato flour were produced from a combination of variety and processing methods. Each sample was evaluated for 35 quality parameters such as chemical, physicochemical and pasting properties. FA resulted in nine factors and identified five pasting viscosities as variables that are more relevant to the variances among the flours. Three clusters were selected which revealed different characteristics among the flour samples. The characteristics provided some information which hitherto were not apparent due to the large data; flours from yellow-fleshed sweetpotato varieties have high paste viscosities while flours from white-fleshed and orange-fleshed varieties have relatively lower paste viscosities; untreated or native flours have high paste viscosities while treatments such as soaking in water, soaking in metabisulphite or blanching caused a lowering of paste viscosities of the flours; sun drying resulted in higher paste viscosities of sweetpotato flours compared to oven drying. DFA showed that 94% of the flours were correctly classified. Two discriminant functions were derived, the use of which improved the classification of the flours. DFA also showed that only four pasting viscosities gave the most efficient combination for classifying the flours, with peak viscosity having the highest positive correlation. This suggests that peak viscosity was the most discriminating property for sweetpotato flour and hence an important index for its quality evaluation.