Radwan S. Farag

Safety evaluation of olive phenolic compounds as natural antioxidants

Free and total polyphenolic compounds were extracted from the fruits and leaves of the Picual cultivar. The safety limits of these compounds were recognized by measuring the activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and the levels of high-density lipoprotein (HDL) cholesterol and total lipids of rat serum. The free and total phenolic compounds (400, 800, and 1600 ppm) and butylated hydroxy toluene (BHT) (200 ppm) were daily ingested for 7 weeks. The administration of olive total and free phenolic compounds at 400 and 800 ppm did not cause any significant changes on ALT and AST activities and serum total lipids. These compounds at 1600 ppm caused significant increase in ALT and AST activities and the content of total lipids. Both olive phenolic compounds were superior to that of BHT in increasing HDL-cholesterol level. Nutritional experiments demonstrated that BHT at 200 ppm caused an enlargement in the kidney and liver of the rat compared with the administration of total and free olive phenolic compounds at 1200 and 1600 ppm. Microscopical examination of kidney and liver tissues of rats administered free and total phenolic compounds at 1200 ppm had the same histological character as that of control rats, while the administration of BHT (200 ppm) and phenolic compounds (1600 ppm) induced severe damage to the tissues of the rat kidney and liver.

Comparative study on the deterioration of oils by microwave and conventional heating

Refined cottonseed oil and hydrogenated palm oil were heated by two methods, conventionally by gas-cooker (deep fat frying) and by microwave energy. Quality assurance methods such as refractive index, color, diene content, acid value, peroxide value, thiobarbituric acid value, iodine value, petroleum ether insoluble oxidized fatty acid content, and degree of polymerization were determined. Exposing the oil samples to various heating times and microwave oven power levels caused some hydrolysis to free fatty acids and accelerated the formation of hydroperoxides and secondary oxidation products. The value from each test increased with both the power settings of the microwave oven and the time of heating. In general, the development of rancidity for refined cottonseed oil heated by microwaves was twice as fast as that produced by conventional heating. Also, the chemical values indicating deterioration for refined cottonseed oil were much higher for refined cottonseed oil than for hydrogenated palm oil in all cases. Gas-liquid chromatographic analysis of fatty acids obtained from the heated oils indicates the occurrence of oxidative degradation and production of short-chain acids.

Aflatoxin destruction by microwave heating

Microwaves were used in the present work in order to destroy pure aflatoxins (model system), and yellow corn and peanuts containing aflatoxins (food system). Pure aflatoxins (B1, B2, G1 and G2) were individually coated on a silica gel and exposed to microwaves at various power settings and periods. The same technique was adopted for peanuts and yellow corn deliberately infected by Aspergillus flavus. The aflatoxins were extracted, fractionated by thin-layer chromatographic technique and quantitatively determined by spectrodensitometry. In all cases, the content of different aflatoxins in the deliberately infected yellow corn was in the decreasing order B1 = G1 > B2 > G2. Infected peanuts were characterized by the highest B1 level, being approximately 3, 2, and 4.4 times as great as that in B2, G1 and G2, respectively. The rate of aflatoxin destruction of model and food systems increased with the increase of microwave oven power setting (low, moderate and high) and exposure time to microwaves.

Influence of gamma-irradiation and microwaves on the antioxidant property of some essential oils

The antioxidant property of anise, caraway, cumin and fennel essential oils extracted from untreated, gamma-irradiated and microwaved fruits against sunflower oil oxidative rancidity was evaluated. The fruits were exposed to gamma-irradiation at 10 KGy and to microwaves at low oven power setting for 1 min. The essential oils were added individually (200 ppm) to sunflower oil and the rate of oil oxidation was followed by determining the peroxide value during storage at room temperature. The irradiated and microwaved essential oils exhibited an antioxidant activity and was superior to that of sunflower oil catalysed by a mixture of BHT + BHA (200 ppm) in most cases. The present data show that gamma-irradiation and microwave treatments did not affect the antioxidant property of the essential oils under study. In addition the essential oils extracted from the gamma-irradiated fruits were more effective as an antioxidant in sunflower oil than those produced from microwaved fruits.

Stabilization of olive oil by microwave heating

Olive fruits of Picual and Shemlalli cultivars were exposed to microwaves generated from an oven at low and moderate power settings for 9 and 12 min. The gross chemical compositions of the non-microwaved and microwaved fruits of both cultivars were determined. In general, the data show that microwave treatment did not cause any change in the fruit components of Picual and Shemlalli cultivars. The stability of extracted olive oil samples from the fruits of both cultivars was followed up by determining the lipase and lipoxygenase activities during storage. The effect of microwave heating on the lipase and lipoxygenase activities of olive oil samples was dependent upon the oven power level, the moderate power setting of the microwave oven produced the least free fatty acid and hydroperoxide contents respectively. The results demonstrated that microwave treatment obviously decreased the enzyme activities during storage and consequently increased the stability of olive oil.

Biochemical and microbial studies on the efficiency of some coating materials for egg preservation

Five coating materials (paraffin oil, starch, gelatin, dextrin and formaldehyde-urea polymer) have been selected to seal the eggshells of eggs laid by white Balady hens (a native Egyptian breed). The uncoated and coated eggs were stored at room temperature (30 ± 2d`C) and in a refrigerator (5 ± 1d`C), and periodically examined microbiologically and chemically. The number of total microorganisms located on the outer surface of uncoated and coated eggs was slightly increased with increasing the storage period up to 30 days. Thereafter, a decrease occurred on the total microbial count from 30 to 60 days in all cases except in eggs coated with gelatin. On the other hand, no bacterial growth was detected in the whole internal egg constituents. The chemical parameters (acid value, free amino acids, total reducing sugars and hydrogen sulfide) were generally increased with time during storage of uncoated eggs at room temperature. The mode of reaction type, i.e. gradual increase or an autocatalytic, for the produc...