Valorization of Apple Pomace as a Multifunctional Ingredient for the Development of Functional Foods

Food waste and by-products, produced in all the phases of the food supply chain, represent valuable sources of multifunctional ingredients to be exploited for the development of functional foods and nutraceuticals. In line with the priorities of the European Green Deal and the Farm to Fork strategy for a healthy and environmentally friendly food system, there is an urgent need of innovative processes and products to facilitate the transition towards a healthy and sustainable diet and favor the shift from a linear to a circular economy [1]. In this frame, the search for innovative and sustainable extraction methods based on the principles of green chemistry to isolate the bioactive compounds from agro-food waste is a challenge [2]. Among food by-products, apple pomace, the press cake resulting from apple juice production, contains plenty of compounds with nutritional and health properties, among which dietary fiber, minerals, and phenolic compounds [3]. Based on these premises, the results of research activities aimed to exploit the nutritional/health properties of apple pomace will be shown. First, apple pomace phenolic fraction was investigated by developing and optimizing an ultrasound-assisted extraction procedure. The fractionation of apple pomace extract was also performed to obtain free and bound phenols, and hydrolyzed fractions in acid and alkaline conditions. The total extract and the different fractions have been characterized by UHPLC/q-TOF MS analysis and it was found that phloridzin and different glycosylated forms of quercetin were the most abundant phenolic compounds. In vitro antioxidant activity, measured by spectrophotometric assays, showed interesting antiradical and reducing properties of apple pomace extracts. The subsequent steps of the research activity concerned with the design, formulation, and study of functional foods, enriched with apple pomace, based on a zero-waste approach. In particular, apple pomace-added meat products, such as beef burgers and swine salami, were developed and their quality attributes, including physicochemical, textural, nutritional, and sensory characteristics, were investigated. The outcome of these investigations is promising as the addition of apple pomace, rich in fiber and phenolic compounds, improves the nutritional and health properties of meat products. In fact, low-fat, fiber- and antioxidant/antimicrobial-rich products can be prepared, avoiding or reducing the addition of additives such as nitrites and nitrates. The results of the recent investigation on the role of apple pomace in the formulation of an innovative healthy mayonnaise will also be presented. Besides the emulsifier and thickening capacities of this by-product, apple pomace-based innovative dressing showed relevant health properties. In fact, an egg- and cholesterol-free mayonnaise characterized by the presence of bioactive compounds can satisfy health-conscious consumers, also meeting the demand of those who prefer plant-based foods.