Effects of Gamma Irradiation on Proteins and Fatty Acids of Soybean

Two hundred grams of soybean seeds (moisture contents of 7.4, 15.3, 22.5, and 30.5%) were irradiated at dose levels of 0, 1, 5, 10, 20, 40, 60, 80 and 100 KGy using Cobalt-60 source. Radiation dose of 100 KGy caused a decrease in the percentage of nitrogen solubility from 80.3 to 67.2, 80.3 to 57.8, and 68.1 to 48.8 when deionized H₂O, 0.6M NaCl, and 0.2M Cacl₂ were used as solvents, respectively. Inhibition of 71% of lipoxygenase activities, 25.4% trypsin inhibitor activities, and 16.7% chymotrypsin inhibitor activities were found when the soybean seeds were irradiated at 100 KGy.     

Effects of Microwave Heating and Gamma Irradiation on Phytate and Phospholipid Contents of Soybean (Glycine max. L.)

The effect of microwave heating and gamma irradiation treatments on phosphorus compounds of soybean seeds were studied. Inorganic phosphorus was significantly (P < 0.05) increased while, phytate and phospholipids were significantly decreased when soybean seeds were microwave-heated for 9 min or more. Furthermore, gamma-irradiation treatments of 20 KGy or more significantly increased inorganic phosphorus and decreased phytate and phospholipids of the beans. Two dimensional thin-layer chromatography was employed to study the phospholipid pattern. Gamma-irradiation at doses from 40 to 100 KGy produced lysophosphatidylcholine and phosphatidic acid. The data of this study showed that, the increase of inorganic phosphorus was mainly due to the decomposition of phytic acids and phosphates of inositol.     

Presence of Nonprotein Trypsin Inhibitor in Soy and Winged Beans

The total trypsin inhibitor was determined in extracts of 11 cultivars of soybeans and 11 strains of winged beans. The proteins in the extracts were precipitated by 16% trichloroacetic acid (w/v), and nonprotein trypsin inhibitor activities were determined in the protein-free supernatants. The nonprotein trypsin inhibitor activities varied between 10.32 ± 1.39 and 24.41 ± 1.04 units/mg defatted soybean samples and in winged beans ranged between 2.65 ± 0.62 and 6.79 ± 0.27 units/mg defatted samples. The nonprotein trypsin inhibitor composed 27–55% of the total trypsin inhibitor activity in the soybeans, and 5–14% of the total activity in winged beans.     

OXIDATIVE STABILITY OF SESAME PASTE (TEHINA)

Tehina samples were prepared from raw, roasted and steamed, or microwaved dehulled sesame seeds from Egypt. Samples contained 54, 96 α 0.36% lipid, 20.68 β 0.19% protein, 3.28 ± 0.05% ash and 1.76 ± 0.06% moisture. The peroxide values (PV) of tehina, stored under Schaal oven conditions at 65C after 35 days, reached 72.2, 86.2 and 97.2 meq/kg for samples prepared from raw, roasted and steamed, and microwaved seeds, respectively. The p-anisidine values (p-AnV) of samples stored under the same conditions and over the same period were 9.3, 10.1 and 10.2, respectively. Meanwhile, both PV and p-AnV of tehina samples stored at room temperature were considerably lower than those kept at 65 C and did not exceed 2.9 and 2.6 meq/kg, respectively. Both PV and p-AnV of tehina samples were lower than those obtained for oils extracted from dehulled sesame seeds which were subjected to similar pretreatment conditions.     

EFFECT OF GAMMA IRRADIATION ON AFLATOXIN B1 PRODUCTION BY ASPERGILLUS FLAVUS IN GROUND BEEF STORED AT 5C

The effect of γ-irradiation for controlling the production of aflatoxin B₁ by Aspergillus flavus in ground beef stored at 5C for 2 weeks was investigated. Aspergillus, Penicillium, Cladosporium, Mucor, Scopulariopsis, Candida and Rhodotorula were the most common fungal genera contaminating ground beef. A. flavus and A. niger were the most common Aspergillus spp. Aspergillus flavus isolates were able to produce aflatoxin B₁ in ground beef. Only 3 (20%) samples of ground beef were contaminated with aflatoxin B₁ (25–45 μg/Kg). Gamma irradiation dose levels resulted in an immediate reduction in the total numbers of A. flavus. No growth or aflatoxin B₁ production occurred at 1.50 kGy during storage.     

Relationship Between Cookability and Some Chemical and Physical Properties of Faba Beans (Vicia faba L.)

Cookability index (determined by penetrometer) and some physical properties were determined for 20 samples of faba beans (Vicia faba L.) grown in Canada and Egypt. Proximate composition was determined for eight samples. Starch of four bean samples, representing extremes in cookability, was examined by differential scanning calorimetry (DSC) and amylography. Statistical analyses showed highly significant correlations between cookability index and hydration coefficient and percentage seed coat for the Egyptian samples (high seed coat content). For the Canadian samples (low seed coat content), highly significant correlations were obtained between cookability index and thousand seed weight, peak amylograph viscosity and falling number values of cotyledon flour. Differences between soft and hard cooking samples were observed by DSC and amylography of the starch. The study showed that the hard to cook phenomenon in faba beans is controlled by characteristics of both seed coat and cotyledons and is not a “hard shell” problem only.     

Effects of Microwave Heating on Solubility, Digestibility and Metabolism of Soy Protein

Microwave heating of soybeans for 9 min decreased protein solubility from 80 to 17%, from 81 to 18%, and from 72 to 16% when deionized H2O, 0.6N NaCl and 0.4N CaCl2, were used as solvents, respectively. Experiments were conducted to determine ‘in vivo protein digestibility and metabolizable nitrogen using male Sprague-Dawley rats. The percentages of true digestibility were found to be 73, 84, 87 and 81 when the soybeans were microwave heated for 0, 9, 12 and 15 min, respectively. Microwave heating soybeans up to 15 min did not alter the fatty acids composition of the beans.     

DISCRIMINATION OF SOME TUNISIAN OLIVE OIL VARIETIES ACCORDING TO THEIR OXIDATIVE STABILITY, VOLATILES COMPOUNDS AND CHEMOMETRIC ANALYSIS

Oxidation stability is a key property of olive oil quality and is affected by different antioxidant compounds whose levels may be influenced by several factors such as cultivar and place of production. Polyphenols, carotenoids, chlorophylls, fatty acids levels and some volatiles were correlated to oxidative stability in olive oils in five samples studied. Total polyphenols and saturated to polyunsaturated fatty acids (and/or oleic to linoleic acid ratio) ratio were shown to be the major parameters in oil antioxidant stability, according to analysis of variance and principal component analysis. The hexanal/E-2-hexenal ratio is a very important indicator of the freshness of the oils and can estimate their oxidation degree.

PRACTICAL APPLICATIONS

The present study gives information about the importance and the variability of some Tunisian olive oil varieties in both their quality (high oxidative stability) and good organoleptic properties which could be appreciated by consumers.