Affiliations: The Natural Resource Research Centre of the University of Latvia, Riga, Latvia
Corresponding author: L. Klavins, The Natural Resource Research Centre of the University of Latvia, Jelgavas street 1, LV-1004, Riga, Latvia. E-mail: [email protected].
Abstract: Blueberries are one of the most popular and widely consumed berries, they are usually consumed fresh, dried or processed into juice. During the production of juices large quantities of berry press residues are generated, which are an industrial by-product and they accumulate as food waste. Optimal management of this industrial fruit by-product could help in utilising berry press residues with the purpose to valorise and add economic value. Blueberry press residues consist of skins and seeds which hold valuable compounds with antioxidant activity –polyphenolics. To facilitate the objective of bioactive compound release, the cell walls must rupture. Pectolytic enzymes could be used to degrade the structural polysaccharides of the berry skin cell wall, thus releasing the contents of the cells into the extraction medium. The physical characteristics of berry skins allows the use of pectolytic enzymes for the disruption of cells; however, the effects of enzymatic hydrolysis could be further improved using ultrasound. In this study the combined effects of enzyme and ultrasonic treatments were evaluated and optimised using the Response Surface Methodology approach in order to increase the release of polyphenolic compounds (especially anthocyanins). The optimised method was further tested to evaluate the application potential of enzyme and ultrasound treatment to prepare blueberry or lingonberry juice with increased antioxidant activity and more vibrant colour. The obtained results provide an optional method of berry press residue valorisation to produce higher quality juice or extract bioactive compounds from this type of food-waste.