Effect of traditional thermal treatment, low temperature low humidity drying treatment and high hydrostatic pressure processing treatment on quality of red plum purée during storage

• Main Authors: Wu, Po-Ya, 吳柏雅
• Other Authors: Huang, Jan-Jeng
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/uw8683

碩士 === 國立嘉義大學 === 食品科學系研究所 === 103 === Hurdle technology is commonly used to preserve fruit purée products by adjusting sugar content, acidity and water activity. However, public acceptability of high sugar fruit purée is relatively low due to the healthy diet concept in this modern age. Thus, developing low sugar content fruit purée by food processing technique is needed to match consumers’preference. Red plum from Tsai He Mountain of Chia Yi District was used as raw material in this study. By adjusting different sugar ratio (5%, 25% and 50%), the red plum purées were processed with five different processing conditions, including traditional thermal treatment (TRA, 100℃ for 30-40 min), low temperature low humidity drying treatment (LTLH, 30℃ for 12 h) and high hydrostatic pressure processing treatment (HHP, 300 MPa, 450 MPa or 600MPa for 3 min), and the processed fruit purée were stored at either room temperature or under refrigeration (4℃) condition. Therefore, the objective of this study was to evaluate the quality changes of red plum purée with different treatment during storage period in order to solve the problem of short storage period of seasonal fresh fruit. There were no significant differences in soluble solid content, moisture content, water activity, pH value and titratible acid content within storage period of 6 months. For color parameter analysis, there was no significant difference in TRA after 6 months storage period at room temperature. In contrast, a* value of HHP group in room temperature changed after 4 months storing and finally decreased 17.6% after 6 months compared to month 0, while HHP treated purée stored under refrigeration could still retain freshly ruby colour. There were no total bacterial counts, mold counts and Escherichia coli and coliforms detected in all treatment groups in microbiological analysis. However, pack expansion occurred in LTLH and HHP 300 MPa groups after 1 month storage in room temperature due to yeast growth up to 3.24-3.57 log CFU/g and 2.74-2.85 log CFU/g, respectively. In-pack gas productions were observed in group HHP 450 MPa and 600MPa/5% and 25% after 3rd and 5th with room temperature storage respectively, and the yeast counts were 2.18-2.32 log CFU/g and 3.22-3.26 log CFU/g. With refrigeration, in-pack gas production occurred in LTLH and HHP 300 MPa groups after 2nd and 3rd month respectively, and the yeast count were 3.36-3.99 log CFU/g and 3.48-4.17 log CFU/g. TRA and HHP 600 MPa groups showed decreases of 33-37% and 21.6-30.1% in anthocyanin content after storing at room temperature for 6 months. With refrigeration storage, there was no significant difference in anthocyanin content in group TRA and group HHP 450 and 600 MPa within 6 months. For total phenolic content analysis, decreasing trends were found in both groups with TRA and HHP 600 MPa treatment within 6 months storing under ambient condition. Yet, there was no significant differences in total phenolic value in group TRA and HHP 450 MPa and 600 MPa under 4℃. Total phenolic content are beneficial for human because it showed a positive correlation between phenolic compound and free radical scarvenging ability. Most enzymes were denaturated after heating in TRA group while HHP treatment could still retain some beneficial enzyme activities compared to fresh fruit purée after 6-month storage, including catalase (CAT) activity for 22.3%, peroxidase (POD) for more than 50%, and superoxide dismutase (SOD) for only 3.4%. Sensory analysis showed that overall acceptability of HHP 600MPa group was lower due to unique sourness, while HHP 300 MPa and 450 MPa showed no significant differences in acceptability score. In conclusion, quality of red plum purée can be highly retained under refrigeration for 6 months after treatment of 450 MPa for 3 minute. The treatment could retain color of red plum and at the same time, avoid changes in composition and remain the activity of CAT and POD. Therefore, a healthier low sugar content red plum purée product can be developed to meet people’s dieting habit with a combination of sugar level/acidity adjustment and HHP 450 MPa treatment.