Antioxidants in some food industry by-products and wastes

© 2011 Dr. Wei Wei TowFruits and vegetables waste by-products generated by the food industry could be utilized as a good source of cheap antioxidants for improving human nutrient supply, contributing to food preservation, and reducing the risks of diseases caused by oxidative damage, such as cancer. Unfortunately, many economical and technological limitations have interfered in the past with appropriate utilization or re-cycling of this high antioxidant potential food industry waste. Consequently, the disposal of such wastes has contributed to environmental pollution, and increased the cost of disposal from the food factory. This study aimed to develop new methods for extraction, and utilization of industry waste by-products, and to examine the possible application of the isolated antioxidants to improve diet and health of human beings. The thesis reports on assessments of different antioxidant extraction methods, quantification of antioxidant contents (HPLC and Follin-Ciocalteu), antioxidant activities (DPPH, ABTS and FRAP), antiproliferation effects (HeLa, HepG2, HT-29 human cancer cells), antimicrobial effects (Escherichia coli K-12, Salmonella enterica serovar Sofia and Listeria innocua) and possible application of isolated antioxidants and the processed food industry waste by-product in commercial food products. Freeze drying and grinding of actual industry tomato and apple waste before antioxidant (carotenoids and polyphenols) extraction, significant (p<0.05) improved the rate of antioxidant recovery by 2.8 and 4.1 fold as compared to their controls. Further study of freeze dried industry apple waste revealed that the total polyphenolic content of non-extractable polyphenols reached 539.84±8.90 mg as gallic acid equivalents /1g of dry wt. in comparison to 77.26±11.53 mg dry wt. in extractable polyphenols. The antioxidant activities of non-extractable polyphenols reported as % reduction in DPPH and ABTS were 89.76±0.93% and 99.78±0.38 %, respectively. However, the extractable polyphenols showed significantly lower (p<0.05) % reduction in DPPH and ABTS, which were 43.58±0.50% and 82.46±0.13%, respectively. Additionally, non-extractable polyphenols at the concentration of 1mg/ml had significant inhibitory effects (46.2% to 95%) against human HeLa, HepG2 and HT-29cancer cells after 3 hours incubation, where as extractable polyphenols showed lower effect (3.9% to 45.1%). The new developed polyphenol extraction method using 50% ethanol (Method C), was the most efficient, cheapest and easy to use method, and yielded the highest amount of extractable polyphenols as compared to method A (80% methanol) (D’Angelo and others 2007) and modified method B using 80% ethanol (Jing, 2010). A similar trend was observed in non-extractable polyphenols isolated from freeze dried industry plum waste, which also was higher in polyphenol content, antioxidant activities and antiproliferation effects than the extractable polyphenols. The total count of Escherichia coli K-12 and Salmonella enterica serovar Sofia was reduced by 5 log10 CFU/ml when adding 2 to 4% of freeze dried industry apple and plum waste (before polyphenol extraction) into the agar medium. Further study of antimicrobial effects of extractable and non-extractable polyphenol extracts isolated from freeze dried apple and plum waste also revealed significant (p<0.05) bactericidal effects against Escherichia coli K-12 and Salmonella enterica serovar Sofia. A reduction rate of 5 log10 CFU/ml was achieved using 40 to 80 μg/ml of isolated antioxidants. Fortifying a commercial peach snack product with 3% and 6% of freeze dried industry apple waste increased the total polyphenolic content by 50%. Additionally, the antioxidant activities using DPPH and ABTS increased by 26.05% and 30.44%, respectively. An increment of approximately 1.6 fold of FRAP value was also recorded. Moreover, the total dietary fibre content was also significantly (p