Evaluation of ultrasound treatment on wine protein stability
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2019
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Zamorano: Escuela Agrícola Panamericana, 2019
Resumen
Haziness is among the most important factors in a high quality wine. Consumers expect a clear solution, even when this does not interfere with olfactory and gustatory characteristics. Ultrasound at 20kHz produces cavitation, which results in colloidal particles collapsing due to pressure increase in the medium. The objective of this study was to evaluate ultrasound effects on protein behavior and stability. Two white wines were submitted to protein stability analyzes, including thermal stability, cold tannin test, ProtoCheck®, particle size, surface electrical charge (SEC) and protein qualification. Randomized complete block designs with factorial arrangements were applied with two times and three amplitudes (phase I) and a similar arrangement including the effect of bentonite (phase II). Thaumatin-like proteins (responsible for haziness) were observed in both wines. Some combinations of amplitude and time were effective in turbidity reduction. In most cases, 90% amplitude was most effective reducing turbidity, although not always reaching total wine stabilization. Cold tannin test revealed that samples subjected to 60 and 90% amplitude reached stability (26-30 NTUs). SEC analysis showed changes in charge due to ultrasound application, requiring different amounts of cationic polymer to neutralize solutions (phase I). Bentonite addition resulted in a generalized protein stabilization. Bentonite concentration was too high to determine ultrasound effectiveness, except for SEC, where combination of ultrasound and bentonite resulted in decrease of protein reactivity. Further investigations should focus on identifying adequate bentonite concentrations to work in combination with ultrasound, determine ultrasound effect on protein concentration and conduct electrophoresis to identify wine protein structure.
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Amplitude, Cavitation,, Colloids, Sonication, Turbidity