INFLUENCE OF SALTS AND pH ON THE FIRMNESS OF COOKED SNAP BEANS IN RELATION TO THE PROPERTIES OF PECTIN

Solute conditions inside cooked bean pods were adjusted by soaking the pods in different solutions. Interactions of Ca⁺⁺ and Na⁺ showed increasing firmness as Ca⁺⁺ concentration was raised and decreasing firmness as Na⁺ was raised. Chelating agents removed Ca⁺⁺ and decreased firmness. Higher pH gave lower firmness except in the presence of excess Ca⁺⁺. The presence of Na⁺ decreased the effect of pH on firmness. Urea decreased firmness when pods had been previously treated with a chelator. The effects of treatments on firmness were related to the behavior of pectin solutions and gels.     

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 .     

SOAKING, BOILING AND ANTINUTRITIONAL FACTORS IN PIGEON PEAS (CAJANUS CAJAN) AND COWPEAS (VIGNA UNGUICULATA)

The effects of soaking, boiling and combination of soaking and boiling at various treatment levels on the detoxification of trypsin inhibitor, cyanogenic glycoside, hemagglutinin, alkaloids and tannin in pigeon pea and vegetable cowpea were studied. Soaking was carried out for 6, 12 and 18 h while boiling was carried out for 40, 60 and 80 min. In combined soaking and boiling method, the beans were soaked for 12 h and then boiled for 40, 60 and 80 min. The results showed that the most effective method of detoxifying any of the toxicants was soaking for 12 h and boiling for 80 min. This method was able to reduce the trypsin inhibitor from 12.45 to 2.59 TUI/mg in pigeon pea and 25.60 to 3.20 TUI/mg in vegetable cowpea. The method also reduced the hemagglutinin content from 27.88 HU/mg to nil and 49.50 to 9.52 HU/mg; the cyanogenic glycoside from 40.50 mg/kg to nil and 83.81 to 5.06 mg/kg; alkaloids from 0.26 to 0.16% and 9.61 to 0.50%; and tannin from 1.60% to nil and from 3.42 to 1.28% in pigeon pea and vegetable cowpea, respectively. This method was found to be more potent in eliminating any of the toxicants rather than soaking or boiling alone.     

AKARA-MAKING CHARACTERISTICS OF FIVE U.S. VARIETIES OF COWPEAS (VIGNA UNGUICULATA)

Akara‐making characteristics of five U.S. varieties of cowpea were determined, using a small‐scale method developed based on 50 g dry seed starting material. Blackeye, crowder, pinkeye, white acre and a new breeding line (white‐eye) cowpeas were evaluated at three paste moisture contents (63, 65, 67%). Blackeye cowpeas at 65% paste moisture served as the control. Ranges for color characteristics were: lightness (L*), 59.8 to 68.3 (control = 61.9); chroma (intensity), 34.6 to 41.4 (control=38.3); hue angle (light brown), 72.7 to 78.6 (control = 74.9); total color difference, 12.8 to 14.9 (control= 14.0). Akara ball hardness ranged from 9.7 to 18.9 N (control= 14.2). Ranges for other texture characteristics were: elasticity, 1.79 to 3.18 mm (control=2.35); cohesiveness (ratio), 0.20 to 0.34 (control=0.23); gumminess, 2.45 to 4.61 N (control=3.23); and chewiness, 4.39 to 14.2 Jx10^3‐ (control=7.59). Each variety produced four to five balls per batch with weights ranging from 17.54 to 21.24 g (control=21.06 g). Paste with overall handling characteristics (ease of dispensing, ease of ball formation) and akara‐making quality (shape of ball, appearance of ball surface) the most like the control was the white‐eye, while crowder was the least like the control.     

CHANGES IN COOKING AND TEXTURAL PROPERTIES OF SPAGHETTI COOKED WITH DIFFERENT LEVELS OF SALT IN THE COOKING WATER

The effect of cooking water on textural and cooking properties of spaghetti was examined using four different salt concentrations 0, 1, 2, 3 and 4% in the cooking water and two types of spaghetti. Brand A was normal durum wheat spaghetti and brand B was spaghetti enriched with bran. Regardless of the cooking water used, brand B was harder, less sticky than brand A and it absorbed less water. Brand A required less cooking time. As salt concentration increased cooking time and hardness scores increased. Adhesiveness values were highest at the early stages of cooking and declined as cooking time increased.     

EFFECT OF ALKALI AND ALKALI-EARTH HALIDES ON TEXTURE AND COOKING YIELD OF COOKED COMMINUTED LEAN PORK

The effects of alkali-and alkali-earth halides and sulfates on the texture and cooking yield of cooked lean comminuted pork were examined. Divalent cations (Ca²⁺ and Mg²⁺) associated with Br⁻, I⁻ and SO^2-₄ imparted a firm texture to meat (peak force values of 17.1–21.1 kg as compared to 8.4 kg for the control sample devoid of any added salt). Peak force values of samples containing monovalent cations were generally low, but for most cases, were higher (P < 0.05) than that of the control. The cooking yields of samples containing divalent cations (regardless of their anion counterparts) were not different (P>0.05) from that of the control. At 200 meq/kg sample, iodides of monovalent cations as well as sodium chloride increased the cooking yield by approximately 5–20% compared to the control.     

GLYCEMIC AND PHYSIOCHEMICAL PROPERTIES OF FIVE COMMON COWPEA (VIGNA UNGUICULATA) CULTIVARS IN NIGERIA

The physicochemical and physiological properties of five commonly consumed cowpea cultivars in Nigeria were assessed. The cultivars examined included Sokoto, Patasco, Iron beans, Isiocha and Ife brown. Ife brown had the most interesting physiochemical properties. It had the highest blue value index of 51.2, highest emulsion capacity of 3.5 g/g and the shortest cooking time of 30 min. Sokoto took the longest cooking time of 62 min. The cowpeas had glycemic responses ranging from 131.4 to 227.5 mg/dL against 369.5 mg/dL for white bread. The values for the glycemic index (GI) of the cultivars were on the low side (0–55) with the exception of Patasco, which had an intermediate GI of 61.57. Ife brown was found to exhibit a defined sinusoidal blood glucose curve. The incremental area under the blood glucose curve for Ife brown was also the smallest (P = 0.05) among the cultivars. This indicated, within the limit of this experiment, that this cultivar exerted the least stress on metabolic blood sugars of volunteers. Ife brown is considered the best in terms of managing physiological changes in blood sugar.     

EFFECT OF FROZEN STORAGE ON THE QUALITY OF AKARA, FRIED COWPEA (VIGNA UNGUICULATA) PASTE

Akara, a fried food of West African origin, is made from whipped cowpea paste flavored with fresh onion, fresh hot or bell pepper, and salt. Akara has potential for U.S. markets as a fully cooked, frozen, reheatable product. Akara was stored at ?18°C for 9 months and compared to freshly prepared akara in selected quality characteristics. Frozen, thawed akara had a higher moisture and lower crude fat content, required significantly less force to shear, and had a lighter, less intense color than freshly prepared product. Frozen/thawed/reheated akara received lower senson scores for color, moistness and flavor than the fresh product. Analysis of headspace volatiles of freshly prepared akara and akara frozen 3, 6 and 9 months resulted in fifteen peaks. Two peaks were significantly affected by frozen storage.     

INFLUENCE OF UNIAXIAL COMPRESSION RATE ON RHEOLOGICAL PARAMETERS AND SENSORY TEXTURE PREDICTION OF COOKED POTATOES

The effect of uniaxial compression rate (20–1000 mm/min) on the parameters: Stress (σ_ftrue), strain (ε_fHencky) and work to fracture (W_f), modulus of deformability (E_d), maximum slope before fracture (E_max) and work during 75% compression (W_total) was investigated for ten potato varieties. Multivariate data analysis was used to study the correlation between and within the sensory and nonsensory measurements by Principal Component Analysis (PCA) which showed σ_ftrue, E_max, W_f, and W_total to explain the same type of information in the data, and ε_fHencky versus E_d another type of information in the data. The deformation rate had a large effect on ε_fHencky. Nine sensory texture attributes covering the mechanical, geometrical and moistness attributes were evaluated. Relationships between uniaxial compression data at various deformation rates and the sensory texture attributes were studied by Partial Least Squares Regression (PLSR). A minor effect of deformation rate on the correlation with the sensory texture properties was obtained. Mechanical properties were predicted to a higher extent than the geometrical attributes and moistness. The prediction of the mechanical, geometrical and moistness attributes increased largely by using uniaxial compression supplemented by chemical measures such as dry matter and pectin methylesterase, but here no relevant effect of deformation rate was obtained.     

INFLUENCE OF SALTS AND pH ON THE FIRMNESS OF OLIVES IN ACID CONDITIONS

The effects of NaCl and CaCl₂ on the texture of olives, both treated and untreated with NaOH, at pH values lower than 4.0 were determined. Firmness of green olives declined as the pH decreased when calcium ions were not added. Calcium ions inhibited the softening rate of fresh and Spanish style green olives although this inhibitory effect depended on the pH. This firming action of calcium was higher at lower pH for fresh olives and at higher pH values for Spanish style green olives. The inhibitory effect of calcium on softening rate diminished as the concentration of cation increased. The presence of NaCl did not have any effect on the texture of either type of green olives. Lactic acid increased the softening rate of green olives by a higher proportion than acetic acid.     

EFFECT OF COOKING ON THE PROFILE OF PHENOLICS, TANNINS, PHYTATE, AMINO ACID, FATTY ACID AND MINERAL NUTRIENTS OF WHOLE-GRAIN AND DECORTICATED VEGETABLE COWPEA (VIGNA UNGUICULATA L. WALP)

ABSTRACT

An experiment was conducted to determine the profile of phenolics, tannins, phytate, amino acid, fatty acid and mineral nutrients in whole‐grain and decorticated vegetable cowpea before and after cooking. Two cowpea varieties: C‐152‐White, having big grain and S‐1552‐White, having small grain with black eye were used for the study. Decortication of cowpea grain resulted in significant reduction (P ≤ 0.05) of total phenolics, total tannins and phytate contents of the two cowpea varieties. Comparison showed that cooking resulted in 19, 28, 28 and 37% losses in phenolics in whole‐grain C‐152, decorticated C‐152, whole‐grain S‐1552 and decorticated S‐1552, respectively. After cooking, whole‐grain and decorticated C‐152 retained 52.1 and 57.7% tannins while S‐1552 retained 59.4 and 49.5%, respectively. In the whole grain, C‐152 lost 72.2% phytate after cooking while S‐1552 lost 70.3%. For the decorticated samples, C‐152 lost 72.4% phytate after cooking while S‐1552 lost 71.2%. For the two cowpea varieties, decortication resulted in significant (P ≤ 0.05) losses of Ca, Fe, Mn, Mg, Zn, K and Cu while there was no significant effect on protein and amino acid profile. Cooking did not cause any significant change in the mineral nutrient composition of either the whole‐grain or decorticated cowpea. For the two cowpea varieties, bulk of the fat consisted of palmitic acid (23.2–27.3%) and stearic acid (53.5–59.8%) in the ratio of 1:2, approximately. Upon cooking, losses of crude protein were recorded in the whole‐grain and decorticated samples of the two cowpea varieties.

PRACTICAL APPLICATIONS

Cowpea is an important cheap source of protein particularly for the low‐income countries, especially in Africa and Asia. However, there is the need for some pretreatments before its cooking because of the presence of some undesirable antinutrients which often cause flatulence after consumption or they can render some minerals unavailable for body assimilation. This study investigated the role that African traditional method of decortication and cooking could play in reducing the concentration of antinutritional factors. We also showed how the traditional treatments could affect the other nutritionally important component of cowpea.

     

CHEMICAL COMPOSITION AND NUTRITIONAL POTENTIAL OF VIGNA UNGUICULATA SSP. CYLINDRICA (FABACEAE)

Seeds of Vigna unguiculata (L.) Walp. ssp. cylindrica (L.) Estt. (Fabaceae) were analyzed for proximate composition, proteins, fatty acids, minerals, antinutritional factors and phytohaemagglutinating activity. Crude protein, crude fat, ash and nitrogen free extractives constitute 29, 10, 4 and 53%, respectively. The caloric value of 100 g dry matter of seed material was 1737 KJ. The essential amino acids, isoleucine, lysine and tyrosine+phenylalanine are present in higher concentrations as 124.3, 79.5 and 79.1 mg/100 g crude protein, respectively. The unsaturated fatty acids constituted more than 60% of total fatty acids. The seeds were found to be a potential source of minerals such as potassium, calcium, phosphorus, zinc and iron. The antinutritional factors such as total free phenols, tannins, L‐DOPA, hydrogen cyanide and phytic acid contents were determined. The effect of cooking on the levels of nutritional and antinutritional factors was also assayed. Cooking caused reduction of 0.02, 0.59 and 0.36% in the mineral constituents of potassium, calcium and phosphorus, respectively. More than 70% of the antinutritional factors were eliminated and there was an increase of crude fiber content.     

EFFECT OF SQUID LIVER EXTRACT ON PROTEINS AND ON THE TEXTURE OF COOKED SQUID MANTLE

ABSTRACT The liver extract of squid Illex argentinus has a proteolytic activity at pH 2–8, with optimum at pH 2.6–3.1. At pH 6 the enzymes retain about 30 and 55% of the maximum proteolytic activity towards hemoglobin and casein, respectively. In squid mantle meat treated with the extract 24 h at 4C and 20C, the sarcoplasmic and myofibrillar proteins were hydrolyzed to low molecular fractions, as was shown by SDS-PAGE. Soaking isolated collagen fibers in the liver extract resulted after 24 h in almost complete solubilization of the fibers in buffered SDS/urea solutions. The solubilized product contained only low molecular weight components. A significant hydrolysis of the proteins in the squid mantle, treated with the liver extract at 20 or 4C, was accompanied by a decrease in toughness of the cooked product by about 65 and 40%, respectively, as compared to the toughness of untreated cooked samples. Cooking of the mantle directly in the liver extract had practically no tenderizing effect.