engleski

Utilization of fruit by-product for the enrichment of apple puree

Apple and apple products are one of the major fruit and fruit products consumed all over the world. In 2012, Croatian apple production exceeded 110 000 tons, which means that over 10 000 tons is processed in various apple products [1]. This growth in turn has generated several hundred tons of wastes (25–30% solid waste) during the processing of apple products, such as apple juice, jelly and cider, among others. Often only 20% is retrieved as animal feed and the rest 80% goes to landfill, is incinerated or is sent to composting sites which results in release of greenhouse gases [2]. Due to health and environmental awareness, sustainable food production and value addition of agro-industrial wastes are the principal issues in the agro and food processing industry. Apple by-products especially apple peel is an excellent source of natural antioxidants, such as catechins, procyanidins, caffeic acid, phloridzin, phloretin glycosides, quercetin glycosides, and chlorogenic acid, among others. In this study we used apple peel powder as ingredient for enrichment of apple puree. Next to apple peel powder (APP) addition (3%), sugars were also added (1 and 5% of glucose, fructose, sucrose or trehalose), and influence on apple puree phenols (TPC) and antioxidant activity (AA) was studied. Sugar addition, especially trehalose, had significant impact on preservation of apple polyphenols. In freeze–dried samples the addition of lower proportion (1%) of trehalose had the highest impact on polyphenol preservation. The highest levels of polyphenols in frozen purees were measured in samples with addition of disaccharides (S and T). Antioxidant activity exhibit a significant correlation (p<0.05) with polyphenols in both frozen and freeze-dried samples. Apple puree incorporated with APP were higher in phenolics and antioxidant activity than the purees without APP. Better use of the by-product can provide benefits to the apple, and fruit and vegetable industry as a whole, as well as solutions for environment concerns associated with waste disposal. The results indicate that APP could be considered as an alternative polyphenol source or specialty food ingredient for food products or selected functional foods and nutraceuticals.

Apple peel; Phenolics; Antioxidant activity; Trehalose

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