Dehydration of untreated and pre-treated onion slices under vacuum was optimised using the response surface methodology. The effects of the drying temperature (50–70°C), slice thickness (1–5 mm), and treatment (5% NaCl and 0.2% K2S2O5) were observed on the responses, viz. final moisture content, colour change, flavour content, and rehydration ratio of the dehydrated onion slices. Full factorial design was employed for the analysis. Optimisation of the vacuum drying process was achieved based on the criteria of maximum flavour retention, 3–3.5% db moisture content, acceptable colour, and rehydration ratio using numerical technique. The optimum condition for the treated sample was found at 58.66°C drying temperature and 4.95 mm slice thickness. Optimum values of the response parameters, namely the moisture content, colour, flavour content, and rehydration ratio were obtained as 3.5% d.b., 30.33 OI/g dried sample; 4.35 μmol/g dried sample and 4.82, respectively.
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机译：使用响应表面方法优化了真空下未处理和预处理的洋葱片的脱水。观察到干燥温度（50–70°C），切片厚度（1-5 mm）和处理（5％NaCl和0.2％K2S2O5）对响应的影响，即。脱水洋葱切片的最终水分，颜色变化，风味含量和补水率。采用全因子设计进行分析。基于最大的风味保留，3-3.5％db的水分含量，可接受的颜色和水合比的标准，使用数值技术实现了真空干燥工艺的优化。发现处理样品的最佳条件是在58.66°C的干燥温度和4.95 mm的切片厚度下。得到的响应参数的最佳值，即水分含量，颜色，风味含量和复水比为3.5％d.b.，干燥样品为30.33 OI / g;干燥样品分别为4.35μmol/ g和4.82。
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