Effects of processing treatments on the nutritive composition and consumer acceptance of some Nigerian edible leafy vegetables

Leafy vegetables are highly perishable food items and require special processing treatments to prevent post harvest losses. Leafy vegetables to be preserved by canning, freezing or dehydration are normally blanched in order to obtain good quality products. In Nigeria, leafy vegetables are preserved by sun-drying and usedlike freshly harvested vegetables in soups. The effects of these treatments on thenutritive composition and sensory qualities of some edible Nigeria leafy vegetablesare reported. Samples (1kg each) of amaranths (Amaranthus hybridus), fluted pumpkin (Talfaria accidentalis), gnectum vegetable (Gnectum africana), vine  spinach (Basella alba), bush okro (Corchorus olitorus), slippery vine (Asystacia gangetica) and cocoyam leaves (Colocasia esculenta) were washed, cut into thin slices and sundried for 5 hrs daily for 2 days. Samples (1kg) of tomatoes  (Lycopersicon esculentum) were similarly dried for 4 days. The fresh vegetables (1kg each) were blanched in hot water at 1000C for 5-6 min and rapidly cooled to 20C in a freezer. Samples (250g each) of fresh (raw), sun-dried or blanched vegetables were cooked separately for 5min in soups. Sun-drying at 30 ± 10C and RH 80 – 85% for 10hr resulted in a mean moisture loss of 35.6% with insignificant (P>0.05) increases of protein, lipid, crude fiber and total ash. Gnectum vegetable, vine spinach, bush okoro, cocoyam leaves and slippery vine had protein contents ranging from 3.0-5.0. K, Fe, Na, Mg and Ca were the predominant mineral elements analysed while contents of Zn and P were low. Blanching and cooking caused significant (P ≤ 0.05) reductions in the K, Na, Ca, Mg, Zn, Fe, and P contents of the vegetables. The implications of these results on the nutritive value of these  vegetables are discussed. Among the treatments, cooking accounted for 64.3 – 67.5% loss of vitamin C while blanching and sundrying accounted for 44.8-47.1% and 36.8 – 39.6% respectively. Panelists rated the soups significantly (P≤ 0.05) higher for colour, taste, texture, flavour/aroma and overall acceptability  characteristics. Fresh fluted pumpkin soup was rated significantly (P≤ 0.05) higher for colour, taste, texture and flavour/aroma characteristics, while fresh gnectum vegetable soup was highly rated for taste, flavour/aroma and overall acceptability characteristics. Compared with other dried vegetable soups, dried gnectum  vegetable soup had the highest score for colour and taste while dried fluted pumpkin soup had the highest score for flavour/aroma and overall acceptability  characteristics. Generally, panelists preferred the fresh to dried vegetable soups.Key words: Blanching, Sun-drying, Cooked, Vitamin C, Sensory attributes.  Des légumes verts à feuilles sont des denrées tres périssable donc, ils demandent des traitements spéciaux pour éviter des pertes aprés moissure. Des legumes verts  à feuille  à conservation: en boîte, congélation ou déshydration sont  normalement blanchis pour avoir des produits de bonne qualities. Au Nigéria des légumes verts à feuilles sont conservés par le séchage solaire et utilisés pour la préparation des potages comme des légumes frais. L’effet des traitements sur les qualités de la composition nutritionelle et sensorielle de certains légumes verts à feuilles comestibles sont prresentés: Les échantillons (1 kilo chacun) de amaranths(Amaranthus hybridus), La citrouille (annelée) (Telfaria occidentalis), Légume gnectum (Gnectum africana), épinard (Basella alba), feuille de vigne (Asystacia gangetica) et des feuilles de taro (Colocasia esculenta) sont lavés, coupés en petits tranches et séchés sous le soleil 5h par jour pour deux jours. Echantillon (1 kilo) de tomates (Lycopersicon esculentum) sont égalements séchés pendant quatre jours. Ces légumes (1 kilo chacun étaient blanchis dans l’eau chaude à 100°C pour 5 à 6 minutes et rapidement surgélés à 2°C dans un congélateur. Les échantillons (250g chacun) de légumes frais (crus) séchés dans le soleil ou blanchis étaient preparés séparément pour 5 minutes dans les potages. Séchant en soleil à 30 + 1°C et RH80 – 85% pour 10hs on a noté une perte moyenne en moisissure de 35. 6% avec une augmentation insignifiante (P>0.05) en protéine lipide, fibre cru et cendre total. G. africana, B. alba, Corchorus olitolus, Asystacia gangetica, C. esculanta out des protéines qui varies entre 3.0 à 5.0. K, Fe, Na, Mg et Ca étaient les éléments miniraux prédominants analisés; alors que la   composition en Zn et P étailent basses. Le blanchiment et le séchage out causé une réduction significative (P≤0.05) en K, Na, Ca, Mg, Zn, Fe et P dans la composition des légumes traités. Les implications de Ces résultats sur la valeur nutritionelle des légumes sont objets de discussions. Parmi les traitements, la preparation contribue en une perte de 64.3 à 67.5% en vitamines C alors que le blanchiment et le séchage en soleil contribuent une perte de 44.8 à 47.1% et 36.8 à 39.6% respectivement. Les juris out fortement estimé les potages pour la couleur, goût, contexture saveur/arôme et l’acceptabilité dans l’ensemble. Le potage préparé avec la citrouille cannelée  (Telfaria occidentalis) frais a été plus considéré  (P≤0.05) en couleur, goût,  saveur/arôme et. L’acceptabilité dans l’ensemble que les autres potages préparés avec des légumes séchés, le potage préparé avec du  Gnectum africana seché a été estimé le meilleur pour la couleur et le goût alors que le potage préparé avec (Telfaria occidentalis) séché a été estimé le meilleur en saveur/arôome et  l’acceptabilité dans l’ensemble. En général les juris out préférés les potages aux légumes frais aux potages aux légumes séchés.Les mots clés: Blanchiment, séchage au soleil, Préparé ou cuisinié Vitamin C,sensoriel, Attribut.

Isolation and Some Physicochemical Characteristics of isolated starch from two Nigerian varieties of African yam bean (Sphenostylis stenocarpa).

The physicochemical properties of starch samples isolated from two Nigerian varieties of African yam bean (Sphenostylis stenocarpa) cowpea seeds were evaluated and studied. Starch yields were 47.1, 45.9 and 54.6g/100g seed weight for cream seed coat, brown seed coat varieties of African yam bean (AYB) and cowpea seeds, respectively. Cowpea seeds had significantly (p.0.05) higher starch but lower amylose contents than the AYB starches. Chemical analysis showed that AYB starches contained 0.1-0.2% protein, 0.3-0.4% lipid, 0.1% crude fibre and 0.1% ash, respectively. The AYB starches hadirregular shape that varied between oval to kidney shaped granules with mean sizes of 24.8} 3.2ƒÊm. Swelling power of the AYB and cowpea starches increased more rapidly at temperatures between 80-950C. Significant (p<0.05) varietal differences were observed in the solubilitypatterns of the AYB starch samples within the temperaturerange of 70-950C. Significantly (p< 0.05) higher percentage AYB and cowpea starches were solubilized at 80-950C than at 60-780C. The Brabender viscosity patterns showed a stable hot paste viscosity and a tendency for retrogradation

Physicochemical Properties of Fungal Detoxified Cassava Mash and Sensory Attributes of Wheat-Detoxified Cassava Composite Doughnuts.

The physicochemical properties of fungal detoxified cassava mash and sensory characteristics of wheat-detoxified cassava composite doughnuts were investigated. Fungal isolates from soils collected at cassava processing sites were isolated, quantified and identified. Cassava mash from grated tuber was partially dewatered and inoculatedseparately with Candida utilis and Rhizopus stolonifer isolates at 1:100 (w/v) level, then allowed to ferment at ambient temperature (30 ± 1oC,RH 80%) for 48hr. Fermenting samples were withdrawn at 12hr intervals and analysed for changes in pH, cyanide, moisture and proteincontents. Detoxified cassava mash was toasted, blended withwheat flour in a ratio of 1:10 (w/w) and used in the preparation of four composite doughnuts that were assessed for their sensory characteristics. Soil samples from cassava grating site had 103 cfu/g moulds and no yeast while clayey moist soils at the dewatering sites had 104 cfu/g and 105 cfu/g moulds and yeasts cells, respectively. Candida . fermented cassava mash was completely detoxified in 24hrwhile the un-inoculated control and Rhizopus-fermented mash had cyanide content reductions of 91.6 and 97.2%, respectively. Candida-fermented cassava mash yielded an initial pH increase, reaching up to pH 7.27 in 48hr while the Rhizopus-fermented samples showed an initial drop in pH followed by a steady increase after 12hr of fermentation to pH 6.8. There was proteolysis with perceived ammonical odour development in Candida-fermented mashes while thecontrol and Rhizopus.fermented mashes had increased protein contents ranging from 4.6-7.6% and 4.6-7.1%, respectively, after 48hrs. Composite doughnuts containing 24hr Rhizopus-fermented flour compared favourably with wheat doughnuts and was rated significantly (P . 0.05) higher than other composite doughnuts for taste, flavour/aroma and overall acceptability characteristics

Rheological, baking and sensory characteristics of fermented cassava starch-wheat-cowpea blends

The rheological, bread making and sensory attributes of varying replacement levels (0-30%) of wheat flour (WF) by fermented cassava starch (FCS) and WF-FCS blends fortified with cowpea flour (CPF) were evaluated. Dough stretchability remained unchanged up to 10% replacement level of WF by FCS. The energy for dough deformation (W),decreased from 316.1x10-4 Joules/g in 100% WF to 275.8x10-4 Joules/g at 20% WF replacement level. Fortification of WF-FCS blends at higher dilutions (30% replacement level) with cowpea flour gave alveograph values that were comparable with the 70:30 (w/w)% WFFCSmixture but with improved R/L ratio. WF-FCS and WF-FCS fortified with CPF had high gelatinization temperatures (61.4-79.10C) and  71.4-82.10C respectively. Peak and cooked paste viscosities increased with increasing contents of FCS. Protein contents of composite breads ranged from 6.3-9.3%. No significant difference (P>0.05) was observed in the bread characteristics of loaves preparedwith 70:30 (w/w)% WF-FCS and samples fortified with 5 and 9% CPF. Breads made from 5-10% FCS supplemented WF showed no significant difference (P>0.05) from control (100% wheat bread) in sensory panel ratings for crust colour, crumb colour, crust texture, flavour/aroma and overall acceptability characteristics. Up to 20% substitution withFCS (80:20 (w/w)% WF/FCS) and 5% fortification with CPF (70:25:5) produced breads with acceptable loaf volume, specific volume and organoleptic characteristics

Evaluation of Citric Acid Production Potentials of Food Processing Wastes

Objective: To evaluate citric acid production potentials of food processing wastes. Materials and Methods: Samples of domestic wastes generated from peels of Yam (YP), Cassava (CP), red cocoyam (RCP), white cocoyam (WCP), ripe plantain (RP), unripe plantain (UPP) and garri processing chaff (GPC) were washed, oven-dried, pulverized and analysed for their biochemical constituents alongside characterization of their sugar contents. Samples were also reconstituted in mineralized media fortified with glucose at 5.0%(w/v), then autoclaved (121°C/15min), cooled and inoculated at 5.0%(v/v) with Aspergillus niger. The samples were incubated at 30°C for 14 days and evaluated at intervals of 2 days for citric acid yields and residual sugar contents. Results: The total carbohydrate contents of the samples ranged from 67.24-76.42% while the starch contents ranged from 0.84-10.48% and the cellulose contents from 3.14-19.70%. No significant differences (p>.0.05) were observed in the carbohydrate contents of CP, RCP, WCP, RPP, UPP and GPC. Glucose, maltose, and sucrose were the predominant sugars characterize in the samples. Highest citric acid yields were obtained in RPP (108.0mg/l and GPC (103.-mg/l) on the 8th day of fermentation. Lowest residual sugar contents were obtained in GPC on days 6-10 followed by RPP. Conclusion: Maximum acid development in the samples (96.09 – 108.0mg/l) was obtained from 6-8 days of fermentation. The residual sugar contents of the samples vary with the sample types and decreased significantly (p<0.05) with increasing fermentation periods. Keyword: Food processing wastes, citric acid, A. niger, fermentation, residual sugar