Multivalorization of apple pomace towards materials and chemicals. Waste to wealth

Abstract

The work presented here uses apple pomace (AP), an industrial waste from apple juice and cider production as a renewable raw material (RRM), to obtain materials that can be utilized as biocompatible scaffolds for osteoblasts and chondrocytes, employed in tissue engineering, valuable extracts that can be used as nutraceuticals and pectin. All of these have much higher value than the original raw material, pectin can be priced up to 1 euro/g, chlorogenic acid is ca. 120 euros/g, caffeic acid 3-5 euros/g and especially the scaffolds that are usually made by synthetic methods using non-renewable raw materials with high fabrication costs and sold at prices higher than 100 euros/g, while the residues used here have prices lower than 100 euros per ton. Thus, there are clear environmental and financial incentives in transforming this waste material into valuable substances and materials. As indicated in the Graphical Abstract, the procedure followed consists in sequential extractions of antioxidants, pectin and finally the preparation of a biocompatible material, giving priority to the latter due to its importance as a renewable scaffold for tissue engineering. From a literature search, to date, although separate ways of valorisation have been applied to this kind of waste, the sequential multivalorization adopted here, has not been previously attempted. Furthermore, biocompatible scaffolds from AP have not been described.

Antioxidant Compounds Recovered from Food Wastes

“…The modern extraction techniques comprise microwave-assisted extraction, ultrasound-assisted extraction, pressurized liquid extraction (e.g., pressurized hot water extraction), enzyme-assisted extraction, supercritical CO 2based extraction and other emerging techniques [18,[25][26][27]. For maximum valorization, several integrated extraction systems were developed (e.g., biorefineries), in which the wastes are subjected to sequential extraction steps for the recovery of different classes of bioactive compounds which can be further used such as or as raw materials for valueadded chemicals production [17,28,29]. Recently, a new integrated extraction-adsorption process has been developed for production of large quantities of extracts rich in antioxidants.…”

“…Among phenolic compounds found in apple pomace, phlorizin is used as a basic structure for a new class of oral antidiabetic drugs [84]. Other health benefits of apple polyphenols are antioxidant, antihypertensive, anticancer, antidiabetic, and hypolipidemic activities, thus making them appropriate to be used as nutraceutical [29,85]. Many dietary polyphenolic components derived from plants have more efficient antioxidant activity in vitro than vitamins E or C and thus have the ability to lead significantly to the protective results in vivo.…”

Acetone-butanol-ethanol (ABE) fermentation of soluble and hydrolyzed sugars in apple pomace by Clostridium beijerinckii P260

“…Apple (the Rosaceae family, genus Malus), as one of the most widely cultivated fruits, has an increasing production over the past ten years, reaching more than 70 million metric tons production in 2015 [1,2]. About 30% of apples are industrially processed to produce juice, cider, or puree which generate large amounts of pulp, skin, and seed wastes, called pomace.…”

Nutraceutical Properties of Apples and Derived Products (Pomace, Seeds, Peels)

“…After extraction of apple juice, large quantities of byproducts are generated, namely apple pomace, which accounts approximately to 25% of fresh apple weight [67]. Apple pomace, consisting of peel, seeds, core, stems and exhausted soft tissue, has long been recognised as a valuable material for nutritional, pharmacological or cosmetic purposes, as it is rich in dietary fibre and polyphenols [33,53].…”

“…A broad range of applications have been described for apple pomace, namely: scaffold for tissue engineering [67], bioproduction of enzymes, organic acids, biofuels [14], extraction of phytochemicals, animal feed, pectin recovery [38]. These by-products have been regarded as a food additive due to their high content in polyphenols and antioxidant activity [15] and dietary fiber [35].…”