Formation of chromatic indices of grape juice by cryomaceration before ultrasonic treatment

Abstract

Abstract In 2022, the EU included high power ultrasound treatment in the list of approved grape processing methods for winemaking purposes. Acoustic cavitation has been demonstrated to affect chromatic parameters by changing phenolic content quantitatively. Anthocyanins are most affected by high power ultrasound and to avoid colorant degradation, a short-term treatment period has been established [1]. Ultrasound is a type of energy generated by a pressure sound wave. The application of high intensity ultrasound can induce changes in the physical and chemical properties of objects [2]. Liquid exposed to ultrasonic waves changes into tiny bubbles that are filled with vapor. The formation of such bubbles and their further compression is called cavitation. Treatment of grapes with ultrasound causes micro-oxygenation which results in cracking of the skin of the berries and anthocyanins, tannins and aromatic compounds are easily released. Cryomaceration works in a similar way. Cryomaceration is a maceration method that involves lowering the temperature of grape berries to -18℃ for a specified period of time. Under this effect, the intracellular water of berries freezes, and the formed ice crystals rupture the cellular structure, similar to micropigmentation, releasing tannins and anthocyanins [3]. The aim of this study was to determine the effect of cryomaceration on the formation of chromatic parameters of grape juice before ultrasound treatment. Evidence supporting the positive effect of cryomaceration on grape juice color formation was identified and summarized.