Hydrothermal treatments of two cowpea (Vigna unguiculata L. Walp) varieties: effect of micronisation on physicochemical and structural characteristics

The effects of a hydrothermal treatment consisting of tempering (to 41% moisture) and heating to 153 °C (micronisation) on the structural and physicochemical characteristics of two cowpea varieties were studied. The untreated varieties had similar cooking times, although cooked Bechuana white cowpeas were significantly (P ≤ 0.05) softer and had a higher incidence of splitting than Var. 462 cowpeas. This may be due in part to differences in cotyledon structure affecting water uptake during cooking. The hydrothermal treatment changed the physical structure and chemical properties of the cowpea seeds. This led to significant (P ≤ 0.05) reductions in the cooking time of micronised Bechuana white and Var. 462 cowpeas, by 47 and 36% respectively, as compared with control samples. Micronisation caused physical fissuring of the seed coat and cotyledon and significantly (P ≤ 0.05) reduced the bulk density of treated seeds. These changes in the physical structure significantly (P ≤ 0.05) improved the initial water uptake during soaking and cooking, increased the enzyme‐susceptible starch and reduced the protein solubility and hydration capacity of the cowpea seeds. Cooked (60 min) micronised cowpeas also had significantly (P ≤ 0.05) more splits and a significantly (P ≤ 0.05) softer texture than control samples. Copyright © 2005 Society of Chemical Industry     

Cowpea cooking characteristics as affected by micronisation temperature: a study of the physicochemical and functional properties of starch

Bechuana white cowpeas were micronised to three temperatures (130, 153 and 170 °C). Cooking properties of the cowpea seeds and the role of starch‐related properties were studied. In all cases, micronisation significantly reduced the cooking time and thus the time required for the cowpea seeds to attain a suitably soft texture. This was attributed in part to the significant improvement in rate of water absorption during cooking and starch pre‐gelatinisation, as evidenced by loss of birefringence and increased susceptibility of the cowpea starch to α‐amylase digestion. However, micronisation to 170 °C resulted in a severe deterioration in pasting properties of the cowpea flour, possibly due to starch depolymerisation and/or amylose‐associated crosslinking. Owing to these changes, cowpea seeds micronised to 170 °C required a longer cooking time than the other two micronised samples. Flour prepared from cowpea seeds micronised to 170 °C may have limited starch functionality. Copyright © 2006 Society of Chemical Industry     

Micronisation and hot air roasting of cowpeas as pretreatments to control the development of hard-to-cook phenomenon

BACKGROUND: Cowpeas stored under conditions of high temperature and high relative humidity (HTHH) develop the hard‐to‐cook (HTC) defect. Cowpeas with HTC defect require long cooking times, limiting their utilisation. Heat pretreatments are aimed at inactivating the enzymes responsible for HTC defect development. In this study, two heat pretreatments, micronisation and hot air roasting, were evaluated to assess their effectiveness in controlling the HTC defect development in cowpeas after storage under HTHH conditions. RESULTS: Micronisation and hot air roasting as pretreatments reduced the cooking time of cowpeas after storage under HTHH conditions compared with the control. The differences in the effectiveness of HTC defect control between micronisation and roasting were dependent on the degree of phytase inactivation on day 0. Phytase activity was reduced by 45 and 70% by roasting and micronisation pretreatments respectively. Reduced phytase activity was associated with higher phytate and soluble pectin contents in micronised cowpeas than in roasted cowpeas after HTHH storage. This observation is in agreement with the phytase‐phytate‐pectin theory. CONCLUSION: Micronisation was more effective than hot air roasting in controlling the development of HTC defect. This was due to a higher degree of phytase inactivation in micronisation when compared with roasting. Copyright © 2011 Society of Chemical Industry     

Effect of micronisation temperature (130 and 170 °C) on functional properties of cowpea flour

Functional properties of cowpea flour from seeds micronised at two different surface temperatures (130 and 170 °C) were studied. Micronisation (130 and 170 °C) significantly (P ? 0.05) increased the water absorption capacity and least gelation concentration of the flour. The treatment significantly (P ? 0.05) reduced the water solubility and swelling indices, gel strength and foaming capacity of the flour. The changes in cowpea flour functional properties, such as the loss of foaming capacity in flours from micronised (130 and 170 °C) seeds, were associated with significant (P ? 0.05) increase in the surface hydrophobicity and cross-linking of the cowpea protein. SDS–PAGE of the protein-rich fractions revealed changes in the protein subunit profile which included the formation of disulphide bonds and possibly Maillard cross-links. The flour from M-170 °C seeds was significantly (P ? 0.05) darker than was the flour from unmicronised and M-130 °C seeds.     

Phenolic composition and inhibitory effect against oxidative DNA damage of cooked cowpeas as affected by simulated in vitro gastrointestinal digestion

Cowpeas contain phenolic compounds with potential health benefits. The effect of simulated gastrointestinal digestion on phenolic composition of cooked cowpeas and the ability of the digests to inhibit radical-induced DNA damage was determined. A red and a cream-coloured cowpea type were used. The phenolic composition of acetone extracts and enzyme digests of cooked cowpeas was determined using UPLC-MS. Compounds such as p-hydroxybenzoic acid, p-coumaric acid, coumaroylaldaric acid and feruloylaldaric acid were present in the acetone extracts of the cooked cowpeas but were not detected in the enzyme digests. Glycosides of quercetin and myricetin decreased upon in vitro gastrointestinal digestion of cooked cowpeas whereas flavan-3-ols were hardly present except catechin glucoside. The enzyme digest of the red cowpea type was about thrice as effective as that of the cream cowpea type in protecting DNA from oxidative damage. The observation that enzyme digests of cooked cowpeas inhibited radical-induced DNA damage suggests that cowpea phenolics retain some radical scavenging activity after gastrointestinal digestion.     

Effect of simulated gastrointestinal digestion on phenolic composition and antioxidant capacity of cooked cowpea (Vigna unguiculata) varieties

Consumption of diets rich in phenolic compounds has been associated with reduced risk of chronic diseases. The effect of cooking and simulated gastrointestinal digestion on phenolic compounds and antioxidant properties of two cowpea (Vigna unguiculata) types was determined. Phenolic acids, flavan‐3‐ols and flavonols were the main groups of phenolic compounds identified. Cooking and simulated enzyme digestion of the cooked cowpea samples rendered some phenolics less extractable (possibly by promoting binding with other food components) or more extractable (possibly by release of bound forms). Total phenolic contents and radical scavenging properties of the cowpeas were reduced upon cooking, but increased upon simulated enzyme digestion. Cowpea extracts inhibited human LDL oxidation at a concentration of 2 mg mL^?1 possibly due to their phenolic content. Phenolic compounds in cowpea can potentially protect against cardiovascular diseases for which LDL oxidation is a risk factor.     

Gamma irradiation of cowpea (Vigna unguiculata L. Walp) seeds: effect on colour,cooking quality and pasting characteristics

Cowpea seeds were treated to various gamma irradiation doses, and their colour, cooking quality and pasting properties studied. Irradiation at 50 kGy resulted in significant browning (indicated by decreases in L colour value) of cowpea seeds. At 2 and 10 (but not at 50) kGy, irradiation led to significant reduction in cooking time of cowpea seeds possibly through irradiation‐induced degradation of starch and pectic substances (indicated by decreases in peak and final viscosities) leading possibly to enhanced heat and mass transfer within the seed cotyledon and cell wall, respectively. At 50 kGy, the cooking time of cowpea seeds was prolonged significantly owing possibly to extensive polymer cross‐linking occurring within the seeds at this high dose. Splitting of cowpea cotyledons during cooking decreased significantly at 50 kGy, but was unaffected at 2 and 10 kGy. Irradiation resulted in significant leaching of nutrients from cowpea seeds during cooking in a dose‐dependent manner.     

The properties of trona and its effect on the cooking time of cowpeas

Trona (Urao) popularly known in Ghana as kawe is used for medicinal and tenderiser purposes (especially in reducing the cooking time of cowpea). The type of kawe found in Ghana contained predominantly 25.0% sodium with small amounts of other metals. Cooking cowpeas in the presence of kawe reduced the cooking time from 75 to 50 min which represents a saving of time and fuel to the cooker.     

Effect of Different Storage and Cooking Methods on Some Biochemical, Nutritional and Sensory Characteristics of Cowpea (Vigna unguiculata L. Walp)

Cowpeas stored in a hermetic container, jute bag and nitrogen atmosphere at ambient (temperature 21–3°C, relative humidity 72–86%) for 6 months were evaluated for changes in proximate composition, nutritional and sensory qualities when cooked by different methods. Nitrogen storage effectively preserved the chemical composition of the cowpeas and maintained grain with better cooking characteristics than cowpeas stored in other systems. Cooking methods and the storage conditions influenced the cooking time and significantly affected the thiamine loss, rate of proteolysis, in-vitro protein digestibility and sensory qualities of the cowpeas. Cooking the stored unsoaked cowpeas with local rock salt to reduce cooking time had a deleterious effect on both the nutritional and sensory qualities of cowpeas.     

Relating consumer preferences to sensory and physicochemical properties of dry beans (Phaseolus vulgaris)

BACKGROUND: Dry beans (Phaseolus vulgaris) have a range of varieties, colours and sizes. Differences in physicochemical and sensory properties influence consumer choices for beans. This study related consumer preferences to sensory and physico‐chemical properties of selected bean varieties—Jenny, Kranskop, PAN 148, AC Calmont, PAN 150 and Mkuzi—grown in Mpumalanga (MP) and Free State (FS) in South Africa. RESULTS: Significant (P < 0.05) variety, location as well as location × variety interaction effects were found for both physico‐chemical and sensory properties of beans. Jenny‐FS, Mkuzi and PAN 148‐MP beans had relatively long cooking times (>60 min). Some beans (e.g. PAN 150 and Mkuzi beans) were described as bitter, soapy and metallic with a raw‐bean flavour whereas more preferred beans (e.g. Jenny‐MP, Kranskop‐MP) were sweet, soft and with a cooked‐bean flavour. CONCLUSION Apart from small seed size, sensory characteristics such as bitter taste, soapy and metallic mouthfeel and hard texture contributed to consumers' dislike of certain bean varieties. The sweet taste, cooked‐bean flavours, soft and mushy textures of the most accepted varieties seemed to be related to beans with good hydration capacities that facilitated softening during cooking. Copyright © 2007 Society of Chemical Industry     

Dehulling characteristics,sensory and functional properties of flours from selected cowpea varieties

BACKGROUND: The knowledge of dehulling characteristics is very important in the selection of cowpeas for flour production. In this study the sensory and functional properties of cowpea flour as influenced by dehulling method (wet and dry/mechanical dehulling) and cowpea variety (white, maroon and mottled) were investigated. RESULTS: White cowpea showed a significantly different (P < 0.05) and higher dehulling rate (DR > 97%) for all dehulling methods. Maroon and mottled cowpeas were poorly dehulled (DR < 10%) when using the wet method (WD). Dry dehulling (DD) was effective on all three varieties (DR > 94%). The highest yield of flour was observed with white cowpea (80% for DD and 96% for WD). The beany odour intensity of flours was dependent on the method of dehulling used. Flour functionality was more significantly influenced by cowpea variety than by dehulling method. CONCLUSION: Dry dehulling could be recommended for cowpea flour production, as this method was found to be more effective on the selected cowpea varieties. Owing to the observed variation in flour functionality among cowpea varieties, the choice of a particular variety for flour production will depend on the intended use of the flour. Copyright © 2009 Society of Chemical Industry     

Effect of added phosphate and type of cooking method on physico-chemical and sensory features of cooked lamb loins

This study evaluated the effect of brining with phosphates on the physico-chemical and sensory features of sous-vide and roasted cooked lamb. Lamb loins (n = 48) were injected with either 10% w/w of distilled water or a solution containing 0.2% or 0.4% (w/v) of a mixture of phosphate salts. After injection, samples were either sous-vide cooked (12 h—60 °C) or oven roasted (180 °C until 73 °C of core temp.). Expressible moisture, cooking loss, instrumental color, pH, water holding capacity, instrumental texture and sensory properties were evaluated. Brining with phosphates led to lower cooking loss in both sous-vide and oven roasted samples, but only the former showed significantly higher moisture content. Phosphates increased instrumental hardness and shear force values in sous-vide samples, while this effect was not as evident in roasted ones. Toughness was reduced and juiciness was improved as a consequence of phosphate addition. Overall, injection of a phosphate solution appears as a potential procedure for improving sensory textural features of cooked lamb whole cuts.     

Influence of quinoa roasting on sensory and physicochemical properties of allergen‐free,gluten‐free cakes

The objectives of this study were to determine pasting properties of non‐roasted (NR) and roasted quinoa (RQ) and to investigate the effect of RQ on consumer acceptance and physicochemical properties of an allergen‐free, gluten‐free cake formulation. Quinoa seeds were roasted at 177 °C for 15 (R15), 30 (R30) and 45 min (R45), and flours were analysed for pasting properties. Five cakes including a commercial chocolate cake (CCC) and cakes made with NR and RQ flours were evaluated for preference by fifty panelists. Quality parameters included colour, water activity, moisture content, firmness, weight and height. Peak and final viscosity increased with roasting time. The NR cake had the highest sensory scores for appearance, colour and texture. On flavour and overall acceptability, CCC was the highest. Regarding quality data, CCC, NR and R15 cakes had similar L* values, while CCC had the lowest a*, b*, a_w, moisture content and firmness values.     

The effect of drying conditions on the development of the hard-to-cook defect in steam-treated cowpeas

A three‐factor–three‐level Box–Behnken design was used to evaluate the effect of drying time, temperature and humidity on textural and physicochemical characteristics during storage of steamed cowpeas. The treatment significantly improved cooked texture and prevented hardening during storage under severe conditions (42 °C/80% relative humidity, RH). Before storage, the cooked texture of treated samples was between 535–628 and 602 N for the untreated control, and between 516–649 and 1394 N after storage at 42 °C/80% RH. The peak force of stored cowpeas significantly decreased as the drying temperature increased. Steaming and drying reduced phytase activity to 59–64% of the original activity and decreased phytate content from 0.133% to 0.074–0.105%. Drying time had a significant effect on phytase activity whereas all drying parameters significantly affected phytate concentration and water absorption. The drying conditions applied after steaming significantly influences seed characteristics; therefore, selection of optimum drying conditions may be used to control seed quality, especially texture.     

Antioxidant Effect of Poleo and Oregano Essential Oil on Roasted Sunflower Seeds

The objective was to evaluate the stability of sensory and chemical parameters in roasted sunflower seeds supplemented with oregano and poleo essential oils; and the consumer acceptability of this product. Four samples were prepared: plain roasted sunflower seeds (Control = RS‐C), and sunflower seeds added with oregano (RS‐O) or poleo (RS‐P) essential oils or BHT (RS‐BHT). Consumer acceptance was determined on fresh samples. The overall acceptance averages were 6.13 for RS‐C, 5.62 for RS‐P, and 5.50 for RS‐O (9‐point hedonic scale). The addition of BHT showed greater protection against the oxidation process in the roasted sunflower seeds. Oregano essential oil exhibited a greater antioxidant effect during storage than poleo essential oil. Both essential oils (oregano and poleo) provided protection to the product, inhibiting the formation of undesirable flavors (oxidized and cardboard). The antioxidant activity that presents essential oils of oregano and poleo could be used to preserve roasted sunflower seeds.     

Effect of soaking,germination, cooking and fermentation on antinutritional factors in cowpeas

The present work deals with the study of efficacy of some treatments, namely soaking (in water and bicarbonate solution( ordinary and pressure cooking, germination and fermentation in reducing or removal of antinutritional factors usually present in cowpeas (protease inhibitors, tannins, phytic acid and flatus‐producing oligosaccharides (raffinose and stachyose). The results showed that long‐time soaking (16 h) in bicarbonate solution caused remarkable reduction in the antinutritional factors. Pressure cooking was more effective than ordinary. Cooking pregerminated cowpeas was most effective. Fermentation completely removed trypsin inhibitor, oligosaccharides and reduced remarkably phytic acid. However, tannins noticeably increased.     

Consumer Acceptability and Sensory Profile of Cooked Broccoli with Mustard Seeds Added to Improve Chemoprotective Properties

Broccoli, a rich source of glucosinolates, is a commonly consumed vegetable of the Brassica family. Hydrolysis products of glucosinolates, isothiocyanates, have been associated with health benefits and contribute to the flavor of Brassica. However, boiling broccoli causes the myrosinase enzyme needed for hydrolysis to denature. In order to ensure hydrolysis, broccoli must either be mildly cooked or active sources of myrosinase, such as mustard seed powder, can be added postcooking. In this study, samples of broccoli were prepared in 6 different ways; standard boiling, standard boiling followed by the addition of mustard seeds, sous vide cooking at low temperature (70 °C) and sous vide cooking at higher temperature (100 °C) and sous vide cooking at higher temperature followed by the addition of mustard seeds at 2 different concentrations. The majority of consumers disliked the mildly cooked broccoli samples (70 °C, 12 min, sous vide) which had a hard and stringy texture. The highest mean consumer liking was for standard boiled samples (100 °C, 7 min). Addition of 1% mustard seed powder developed sensory attributes, such as pungency, burning sensation, mustard odor, and flavor. One cluster of consumers (32%) found mustard seeds to be a good complement to cooked broccoli; however, the majority disliked the mustard‐derived sensory attributes. Where the mustard seeds were partially processed, doubling the addition to 2% led to only the same level of mustard and pungent flavors as 1% unprocessed seeds, and mean consumer liking remained unaltered. This suggests that optimization of the addition level of partially processed mustard seeds may be a route to enhance bioactivity of cooked broccoli without compromising consumer acceptability.     

Proximate compositions, pasting and rheological properties of mumu– a roasted maize meal

Genetically improved maize variety (TZRS‐W) grains were used to produce mumu– a roasted maize meal. The grains were divided into six treatment groups namely: non‐soaked, non‐cooked (NSNC); non‐soaked, cooked (NSC); soaked, non‐cooked (SNC); soaked, cooked (SC); germinated non‐cooked (GNC); and germinated, cooked (GC). Each group was roasted in the oven at 150 °C for 1 h to produce mumu. No significant differences (P ≤ 0.05) were found in the protein, fat, ash, fibre and carbohydrate contents of the different products. Soaking and germination without cooking resulted in lower breakdown viscosities of the products. The peak viscosity (20.17 Rapid Visco Unit (RVU)) and final viscosity (28 RVU) of the GNC samples were significantly higher (P ≤ 0.05) than the corresponding values (5.17–7.25 RVU) of the NSNC, NSC, SNC, SC and GC products. No significant differences (P ≤ 0.05) were found in the pasting temperatures (63.40–64.85 °C) between all the six groups. Germination for 24 h without cooking may yield poor quality products with low nutrient density.     

EFFECTS OF INFESTATION BY BRUCHID BEETLES (CALLOSOBRUCHUS MACULATUS) ON THE NUTRITIONAL QUALITY AND SENSORY PROPERTIES OF COWPEAS (VIGNA UNGUICULATA)

The effects of insect infestation by Callosobruchus maculatus (Fabricus) on the chemical, nutritional and sensory properties of three cowpea varieties were investigated. Proximate analysis showed that infestation led to an increase in moisture content of seeds by 28.6% on the average. Decreases of 10.6%, 46.5% and 11.4% in crude protein, ash and soluble carbohydrate contents, respectively, were observed. For the three cowpea varieties, the minerals sodium, calcium and magnesium decreased by 6.7%, 10.0% and 1.3%, respectively. Indices of fat deterioration, peroxide value and free fatty acids, increased by 175% and 242%, respectively. Infestation decreased the weight gain, Protein Efficiency Ratio (PER), Feed Efficiency Ratio (FER) and blood glucose levels of experimental rats by 28.5%, 19%, 63.5% and 1.46%, respectively. Infestation also led to significant deterioration of the sensory attributes of food products developed from cowpeas. The color, aroma, taste and texture of these cowpea products were less acceptable than the sensory parameters of products made with uninfested cowpeas .