Effects Of Ultra High Pressure Processing On Microbial Population, Enzyme Activity And Quality Charateristic Of Huyou Juice

Nonthermal food processing technology is a interesting topic in the field of food processing. Of these nonthermal food processing technologies, high pressure treatment has proven to be effective in eliminating all spores and enzymeatic activity and maintaining a good food quality. The effect of ultra high pressure processing on microorganism and pectinmethylesterase (PE) in huyou juice was investigated. A comparative analysis of ultra high pressure to thermal treatments concerning quality charateristic of huyou juice was also conducted.This study investigated the effect of various ultra high pressures (100-600 MPa) and temperatures (20-60℃) and durations (5-25 min) on bacterium, mould and yeast in huyou juice (pH 3.65) were carried out. Of these ultra high pressure treatments, application of 500 MPa for 10 min at 25℃, 400 MPa for 15 min at 50℃or 400 MPa for 15 min at 25℃to huyou juice can well meet the national standard for fruit or vegetable juice hygiene. Furthermore, ultra pressure processing was used to understand the effects of PE activity while the Box-Benhnken model of Response surface methodology (RSM) was adopted to optimize the processing. Pressure, temperature and duration for ultra high pressure were significant factors to inactivate PE activity, with the order of pressure > temperature > processing time. Ten groups of ultra high pressure processing parameters were obtained to inactivate high than 80% PE activity in this study.Ultra high pressure (UHP) and thermal treatments can affect huyou juice quality. Huyou juice exhibited a lower change in color after ultra high pressure processing than thermal treatment. Ultra high pressure treatment maintained L-ascorbic acid of 91.97-98.29%. Both ultra high pressure and thermal treatments increased the average particle size of huyou juice, but did not affect significantly values of ~oBrix and pH. In addition, ultra high pressure and thermal treatments slightly decreased the levels of narigin and neohesperidin and increased little the antioxidant activity in huyou juice.Ultra high pressure processing can better maintain the volatile components of huyou juice, such as D-limonene,γ-terpinene, 4-terpineol, a-terpineol, decanal,β-elemene,γ-elemene andβ-cubebene, compared with thermal treatment. However, it is difficult to distinguish the ultra high pressure-treated juice from the original juice by sensory evaluation method.Ultra high pressure can inactivate microorganisms or enzymes effectively, and the sensory or nutrition quality can be retained mostly. Those complied with consumer demands for high quality foods with natural flavor and taste, and which are free from addictives. With the cost of the equipment reduced and related food standards or regulations established, this technology would have a good opportunity in the future.