Abstract
A cryo-macerated must of V. vinifera L. cabernet sauvignon was processed by ultra-high-pressure homogenisation (UHPH) sterilisation without the use of SO2. The UHPH treatment of the must was carried out continuously at a pressure of 300 MPa and reaching a maximum temperature of 77 °C for less than 0.2 s. The colloidal structure of the UHPH must was evaluated by atomic force microscopy (AFM) measuring an average particle size of 457 nm. The initial microbial load was 4-log CFU/mL (yeast), 3-log CFU/mL (bacteria). No yeast and non-sporulating bacteria were detected in 1 mL and 10 mL of the UHPH-treated must, respectively. Furthermore, no fermentative activity was detected in the non-inoculated UHPH-treated musts for more than 50 days. A strong inactivation of the oxidative enzymes was observed, with lower oxidation (≈ × 3) than controls. The antioxidant activity of the UHPH-treated must was much higher (106%) than that of the control must. UHPH had a protective effect in total anthocyanins, and especially in acylated anthocyanins (+ 9.3%); furthermore, the fermentation produces fewer higher alcohol (-44,3%) and more 2-phenylethyl acetate (+ 63%).
Highlights
Elimination of SO2 is currently a topic of great interest in oenology, and the use of ultra-high-pressure homogenisation (UHPH) to eliminate oxidative enzymes and wild microorganisms is a powerful tool to reach this objective
Must processed by UHPH is affected by ultra-high impact forces, and shear efforts strongly affect the nature of the molecular structure of the colloidal particles
After centrifugation, the colloidal particles appeared intensively dyed in the control (Fig. 2a, left) but only slightly in the must processed by UHPH (Fig. 2a, right), probably because the smaller average size reduces the adsorbent capacity of the anthocyanins
Summary
Elimination of SO2 is currently a topic of great interest in oenology, and the use of ultra-high-pressure homogenisation (UHPH) to eliminate oxidative enzymes and wild microorganisms is a powerful tool to reach this objective. UHPH has an ultrashort in-valve time (< 0.2 s) which helps to protect the nutritional and sensory quality, even when high temperatures can be reached in the valve. Several recent reviews have included the most important features and applications of UHPH processing (Comuzzo & Calligaris, 2019; Morata & Guamis, 2020; Patrignani & Lanciotti, 2016; Zamora & Guamis, 2015). UHPH is more efficient than high-pressure homogenisation (HPH) or microfluidisation concerning the elimination of microorganisms and enzyme inactivation, which normally needs multi-passes for efficient microbial control (Szczepańska et al, 2021).
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