Management of apple and grape processing by-products. A review

Introduction. The by-products from the processing of apples and grapes can be excellent materials for the production of functional foods. In this case, the environment is preserved, and food products are enriched with important nutrients. Materials and methods. A systematization of the latest scientific research in terms of management of the waste from the production of apple juice and grape wine. Results and discussion. By-products of apple and grape processing contain important nutrients such as fibers, minerals, vitamins, polyphenols, and possess high antioxidant activity. In recent years, a lot of research has been conducted to study the application of this type of waste in preparation of different food products (biscuits, cookies, cakes, bread, pasta, noodles, yogurt, cheese, kefir, salami, sausages, patties, and burgers). Regarding the percentages of substitution of conventional flours with by-products of apple and grape processing, variations are observed. For cereal products, the minimum percentage of substitution was 1% and the maximum was 100%. For meat products, the percentages of added by-products of apple and grape processing varied from 1 to 20%, while for dairy products, these contents were between the values of 0.2 and 10%. An improvement in nutrient quality with the addition of by-products of apple and grape processing was observed, such as increase of fiber, total polyphenol, flavonoids, anthocyanins and mineral contents and antioxidant activity. Incorporation of apple and grape processing by-products leads to changes of the volume or height of the products (biscuits, cookies, cakes, and bread), and changes in texture (hardness, crunchiness), appearance (surface properties, color, density), and intensity of smell and taste. It was found that the optimum cooking time of pasta/noodles/spaghetti decreased and cooking loss increased with the increasing amount of incorporated apple and grape processing waste. Addition of these by-products reduced fermentation time and syneresis during yogurt storage. It was found that the addition of by-products of apple and grape processing in the meat products increased cooking yield, emulsion stability, radical scavenging activity, and decreased pH. Conclusions. Use of waste from the processing of apples and grapes in the food industry is an opportunity to reduce environmental pollution, to create new functional and innovative food products, which will be enriched with important nutrients and biologically active substances.