ANTIOXIDANT ACTIVITIES OF EXTRACTS FROM OLIVE OIL AND OLIVE WASTES AND THEIR EFFECTS ON THE SHELF LIFE OF FOOD PRODUCTS

Abstract

In this study, ethanol extracts, ethyl acetate extracts and chloroform extracts of olive leaves, pomaces and virgin oil of picual and coratina cultivars were examined for their antioxidant activities. Coratina pomace ethanol extract had higher antioxidant activity(99.90%)than α-tocopherol (80.40%). Coratina pomace extracts had 97 mg gallic acid/g dried sample total phenols and 23.83 mg rutin acid/g dried sample total flavonoids. E-vanillic, salicylic, pyrogallol, benzoic acid, and catechin were the most abundant phenolic compounds in coratina pomace ethanol extract which represented 82.65% of the total phenolic compounds. Naringin, luteolin, hispertin, and quercetin were the most abundant flavonoid compounds in coratina pomace ethanol extract which represented 85.82% of the total flavonoids compounds. The coratina pomace ethanol extract had 7.53 h induction period of sunflower oil which represented 92.75% of α-tocopherol. Therefore, coratina pomace ethanol extract was selected for improving the shelf-life of carp fillets and carp burgers during storage at 5°C for 16 days. Carp fillets treated with coratina pomace ethanol extract at the concentration of 250 ppm and dipping time of 30 min and stored at 5°C for 16 days had lower TBA values, total bacteria, psychrophilic bacteria, lipolytic bacteria, proteolytic bacteria, total yeast and mold counts and rancid odor (described as very slight) as compared with the untreated sample (described as very strong). Fat retention and juiciness of carp fillets were increased and moisture retention and shrinkage decreased, however, the cooking yield was not affected. Carp burgers treated with coratina pomace ethanol extract at the concentration of 250 ppm and dipping time of 30 min and stored at 5°C for 16 days had lower moisture content, TBA values, total bacteria, psychrophilic bacteria, lipolytic bacteria, proteolytic bacteria and total yeast and mold counts than untreated sample. However, crude protein, crude fat, total ash and total carbohydrate contents had an opposite trend. Carp burgers stored at 5°C for 16 days in nitrogen packaging condition had lower mean TBA values, total carbohydrate than carp burgers stored in air packaging condition either in uncooked or cooked burgers. However, moisture, crude fat, total ash and crude protein contents had opposite trend. The total aerobic bacteria and psychrophilic bacteria counts were reduced by the cooking process either with air or nitrogen packaging conditions. However, lipolytic bacteria, proteolytic bacteria and total yeast and mold counts were inhibited by the cooking process. The uncooked carp burgers had mean rating scores ranged between like moderately (7.0) and like very much (8.0). However, cooked burgers had mean rating scores ranged between neither like nor dislike (5.26) and like moderately (7.0).