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