الفهرس 
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Abstract
The present study was carried out to evaluate the use of some food industrial by-products such as tomato, potato, mandarin, and grape fruit wastes as source of natural antioxidants (phenolic compounds) and to study the effect of ethanolic extracts of these by-products as antimicrobial agents on gram positive and negative bacteria strains. Different amounts of tomato waste extract (TWE) and tomato waste powder (TWP) as a natural antioxidant source were added to raw beef burger and minced meat to study its effects on meat physico-chemical properties, total volatile basic nitrogen (TVBN) and thiobarbituric acid (TBA) as well as microbial loader. The obtained results showed that the moisture content of the tested wastes was 5.80, 4.82, 6.30 and 13.20, respectively. While, crude fat contwnt was 4.59, 2.30, 4.00 and 4.70%, respectively. The crude protein percentage was 12.05, 16.90, 11.45 and 6.50% and those of total carbohydrates were 73.85, 70.18, 75.21 and 72.10%.Total ash percentages were 3.71, 5.80, 3.04 and 3.50%, for tomato, potato, mandarin, and grape fruit wastes, respectively. Tomato waste contained high amounts of total polyphenols followed by potato and grape fruit wastes revealing 367.8, 342.4 and 268.8 mg gallic acid equivalent (GAE) /g extract, respectively. Whereas, mandarin waste had the lowest gallic acid content (226mg GAE/g extract). Ethanol extracts showed antioxidant activity reaches 90.24,91, 19and 26% for tomato, potato, mandarin, and grape fruit wastes by using DPPH as free radical. Significant decreases in TBA values and microbial load were observed in the beef burger and minced meat samples treated with the extract in comparison with the control. Owing to the high contents of antioxidants, tomato peel or its extracts can be used as a food supplement. Besides, the direct addition of dry tomato peel (DTP) to beef burger and minced meat may be useful for obtaining a new product enriched in lycopene and providing new use for this by-product from tomato industry.
Keywords: Tomato wastes, Lycopene, Natural antioxidants, Beef burger, Phenolic and Flavonoids, Sensory evaluation.