Sustainable Approaches Using Green Technologies for Apple By-Product Valorisation as A New Perspective into the History of the Apple

Abstract

The apple has been recognised as the most culturally important fruit crop in temperate land areas. Centuries of human exploitation and development led to the production of thousands of apple cultivars. Nowadays, the apple represents the third most widely cultivated fruit in the world. About 30% of the total production of apples is processed, being juice and cider the main resulting products. Regarding this procedure, a large quantity of apple by-product is generated, which tends to be undervalued, and commonly remains underutilised, landfilled, or incinerated. However, apple by-product is a proven source of bioactive compounds, namely dietary fibre, fatty acids, triterpenes, or polyphenols. Therefore, the application of green technologies should be considered in order to improve the functionality of apple by-product while promoting its use as the raw material of a novel product line. The present work provides a holistic view of the apple's historical evolution, characterises apple by-product, and reviews the application of green technologies for improving its functionality. These sustainable procedures can enable the transformation of this perishable material into a novel ingredient opening up new prospects for the apple's potential use and consumption.

Keywords: apple; apple by-product; bioactive compounds; green technologies; valorisation.

Figure 1

Graphical representation of certain fundamental issues for the European Green Deal.

Figure 2

Evolutionary history of the cultivated apple.

Figure 3

Apple by-product as a source of terpenoids, phenolic compounds, fatty acids, and dietary fibre.

Figure 4

Apple industry based on green and sustainable technologies in the scope of circular economy.

Figure 5

Determination of dietary fibre in apple by-product under high hydrostatic pressure at 200 MPa for 15 min and 600 MPa for 30 min, assisted and not assisted by Celluclast^® (92 EGU) enzyme. Data are expressed as g/100 g dry matter.

Figure 6

SEM micrographs of samples of apple by-product: control (A), HHP-treated at 200 MPa (B) (own photos). The white scale bar on micrographs corresponds to 100 μm. Magnification (referred to the 12.67 cm × 8.82 cm raw picture size) was: (a) × 50₍₁₎, × 500 _(2), (b) × 100₍₁₎, × 300₍₂₎.