超高压和热处理对龙眼干品质特性的影响

Effect of Thermal and High Pressure Treatment on Quality Characteristics of Dried Longan

摘要:

本研究对比分析超高压与热处理在达到延长保藏期的基础上对高水分龙眼干色泽、质构、多酚及抗氧化活性的影响。实验结果表明，相比未处理龙眼干，超高压处理对龙眼干果肉色泽的b*值没有影响，仅较小影响L*和a*值，但显著影响热处理样品的L*、a*和b*值（P<0.05）；热处理则显著影响胶粘性、硬度和粘性（P<0.05），而超高压只显著影响果肉的硬度与粘性且影响远小于热处理（P<0.05），85 ℃处理60 min后果肉的硬度为118.87显著低于400 MPa处理10 min后的样品（232.86）和未处理样品（246.90）（P<0.05）；超高压和热处理都能显著提高龙眼干的多酚含量（P<0.05），且热处理要显著高于超高压处理和未处理样品，但超高压处理样品的抗氧化能力显著高于热处理和未处理样品（P<0.05），其中500 MPa处理20 min时有最高的DPPH清除能力，400 MPa 处理10 min羟自由基清除能力最高，热处理样品的抗氧化能力最低。

Abstract:

The effects of different thermal and high pressure treatments on the color, texture, microstructure, total phenolic content (TPC) and antioxidant capacity of dried longan were investigated. The results showed that the physical parameters of the pulp of high pressure-treated longan only slightly changed compared with those of the unprocessed. High pressure treatment had no effect on yellowness/blueness (b*) and only slight effect on lightness/darkness (L*) and redness/greenness (a*). However, thermal treatment significantly influenced L*, a*, and b*, and caused higher degradation of hardness than that of high pressure treatment. The hardness of the longan pulp treated at 400 MPa for 10 min (232.86) was similar to that of the unprocessed (246.90) and was approximately two-fold higher than that of which treated at 80 ℃ for 60 min (118.87). The TPC of the thermal treated longan was significantly higher than those of the high pressure-treated and unprocessed, and the longan treated at 85°C for 60min had the highest TPC (535.53±14.40 mg GAE/100g DW). However, the 2, 2-Diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radicals scavenging activity of the high pressure treated longan was significantly higher than that by thermal treatment (P<0.05). These results suggested that high pressure treatment effectively retained the color, texture, and antioxidant capacity of dried longan. High pressure treatment can be an efficient method to preserve dried longan quality.