ASPA Group, Department of Food Technology, Universitat Politècnica de València, Camino Vera s/n, 46022 València, Spain; Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy.
Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy.
Food Res Int. 2018 Apr;106:580-588. doi: 10.1016/j.foodres.2018.01.022. Epub 2018 Jan 12.
The low operating temperatures employed in atmospheric freeze-drying permits an effective drying of heat sensitive products, without any impairment of their quality attributes. When using power ultrasound, the drying rate can be increased, thus reducing the process duration. However, ultrasound can also affect the product quality. The aim of this study was to evaluate the effect of various drying process variables, namely air temperature and velocity, ultrasound power and sample size, on the antioxidant properties of eggplant (Solanum melongena L.) samples. For this reason, drying experiments were carried out at different drying temperatures (-5, -7.5, -10 °C), power ultrasound levels (0, 25, 50 W; 21.9 kHz) and air velocities (2, 5 m s) using different sample sizes (8.8 mm and 17.6 mm cube side). The ascorbic acid content (Jagota and Dani method), total phenolic content (Folin-Ciocalteau method), and the antioxidant capacity (FRAP method) of the dried products were considered as quality indicators of the dried samples. The increase in air velocity and temperature, as well as the sample size, significantly reduced the antioxidant potential of the dried samples (p-value < .05). For a given sample size, the application of ultrasound, at the acoustic power levels tested, did not produce significant effects on the antioxidant indicators considered. Temperature measurements inside the drying sample showed a non-negligible temperature rise when acoustic power was applied.
在常压冷冻干燥中采用的低温操作允许对热敏感产品进行有效干燥，而不会损害其质量属性。使用功率超声时，可以提高干燥速率，从而缩短加工时间。然而，超声也会影响产品质量。本研究的目的是评估各种干燥工艺变量（即空气温度和速度、超声功率和样品尺寸）对茄子（Solanum melongena L.）样品抗氧化特性的影响。为此，在不同的干燥温度（-5、-7.5、-10°C）、不同的超声功率水平（0、25、50 W；21.9 kHz）和不同的空气速度（2、5 m/s）下进行了干燥实验，使用不同的样品尺寸（8.8 mm 和 17.6 mm 立方体边长）。干燥产品的抗坏血酸含量（Jagota 和 Dani 法）、总酚含量（Folin-Ciocalteau 法）和抗氧化能力（FRAP 法）被认为是干燥样品的质量指标。空气速度和温度的增加以及样品尺寸的增加显著降低了干燥样品的抗氧化潜力（p 值<.05）。对于给定的样品尺寸，在所测试的声功率水平下应用超声并未对所考虑的抗氧化指标产生显著影响。在干燥样品内部进行的温度测量显示，当施加声功率时，会出现不可忽略的温升。
