Perspective of apple processing wastes as low-cost substrates for bioproduction of high value products: A review

The fruit processing industries are experiencing surge due to the increasing demand of food products as a result of burgeoning human population. Apple and apple products are one of the major fruit and fruit products consumed all over the world. Apple processing industries generate huge quantities of solid and liquid sludge wastes. The solid residues consist of a mixture of skin, pulp and seeds derived from the production of concentrated apple juice, jam, and sweets and are collectively known as 'apple pomace'. Being highly biodegradable, the disposal of these wastes represents a serious environmental problem and presents many challenges. 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. However, advancement in technology has led to the alternative options of utilization of apple pomace. It can be used as a promising raw material for direct extraction of bioactive compounds and bioproduction of high value-added products, such as enzymes, organic acids, biofuels, among other products. This article reviews the work done for value-addition of this precious biomass which can help in setting up integrated process in the existing apple industries itself or separate small scale industries.