Comparing the effects of ultra-high-pressure homogenization and conventional thermal treatments on the microbiological, physical, and chemical quality of almond beverages.

UNLABELLED: The effects of ultra-high-pressure homogenization (UHPH) at 200 and 300 MPa, in combination with different inlet temperatures (55, 65, and 75 °C) on almond beverages with lecithin (AML) and without lecithin (AM), were studied. UHPH-treated samples were compared with the base product (untreated), pasteurized (90 °C, 90 s), and ultra-high-temperature (UHT, 142 °C, 6 s) samples. Microbiological analysis, physical (dispersion stability, particle size distribution, and hydrophobicity), and chemical (hydroperoxide index) parameters of special relevance in almond beverages were studied. Microbiological results showed that pressure and inlet temperature combination had a significant impact on the lethal effect of UHPH treatment. While most UHPH treatments applied produced a higher quality of almond beverage than the pasteurized samples, the combination of 300 MPa and 65 and/or 75 °C corresponded to a maximum temperature after high pressure valve of 127.7 ± 9.7 and 129.3 ± 12.6 °C, respectively. This temperature acted during less than 0.7 s and produced no bacterial growth in almond beverages after incubation at 30 °C for 20 d. UHPH treatments of AML samples caused a significant decrease in particle size, resulting in a high physical stability of products compared to conventional heat treatments. UHPH treatment produced higher values of hydroperoxide index at day 1 of production than heat-treated almond beverage. Hydrophobicity increased in AML-UHPH-treated samples compared to AM and conventional treatments. PRACTICAL APPLICATION: Ultra-high-pressure-homogenization (UHPH) is an emerging technology, a potential alternative to conventional heat treatments. It is a simple process consisting of single step. When liquid food (almond beverage in this study) passes through the high-pressure valve, a very good stability and reduction of microorganisms is achieved, both effects due to the particle breakdown. Specific UHPH conditions could produce commercial sterilization of almond beverage.