Influence of high-pressure homogenization treatments combined with lysozyme activated packaging on microbiological and technological quality of vegetable smoothie during shelf life

In this study the effect of a high pressure homogenization (HPH) treatment, alone and in combination with a biodegradable polylactic acid (PLA) packaging activated with lysozyme on a smoothie made with apple, carrot and rice beverage was evaluated. In particular, the effects of treatments on the microbiological and quality characteristics of smoothies were assessed during storage at 4 and 10 ◦C in climatic chambers at RH of 50 %. Obtained results showed the efficacy of HPH at 100 MPa to reduce the initial cell load of mesophilic and psycothrophic aerobic bacteria, lactic acid bacteria, yeasts and aerobic spore-forming bacteria. Moreover, the combination of HPH and lysozyme activated packaging resulted in an increased antimicrobial effect against mesophilic, psychrotrophic and lactic acid bacteria during product storage at 10 ◦C. Yeast and spore forming bacteria showed, instead, lower cell loads independently from samples. Samples packed in active packaging, both treated and not, showed a better color retention in terms of lightness and red index, compared to control (C) ones both when stored at 4 and 10 ◦C. The HPH treated smoothies, both activated and not, at 4 ◦C remained microbiologically stable for more than 20 days. However, the use of active packaging has also allowed to reduce the microbiological proliferation during storage at 4 ◦C. Moreover, few differences in color indices were highlighted between samples stored at 4 ◦C. Obtained results indicate that the combination of HPH treatment and active packaging may represent a useful strategy to increase safety and shelf-life of vegetable smoothies.