Pomelo (Citrus grandis (L.) Osbeck) is an important cultivar of the Citrus genus, which contains a number of nutrients advantageous to human health. Non-edible parts of pomelo consist of flavedo, albedo, lamella and waste obtained from juice extraction (pulp waste). The peels are also thought to be part of waste products, which generally being discarded. Therefore, the objective of the present study was to evaluate changes in total phenolic contents (TPC) and antioxidant activity of processed pomelo peels after oven drying (50 and 60 °C) and freeze drying treatments in comparison with fresh pomelo peels. A slightly different (4%–6%) in TPC was observed in oven dried pomelo peels in comparison with fresh peels, indicating that there was a slightly effect of post-drying methods on retaining the antioxidant potential of these natural byproducts. In vitro assays revealed that post-drying methods involved oven drying exerted a higher TPC compared to freeze drying in overall parts of pomelo byproducts. Highest retention of bioactive compounds was found in fresh pomelo peels (437–1876 mg GAE/100 g DM), followed by oven dried at 50 and 60 °C (892–1336 mg GAE/100 g DM), and freeze dried (555–1267 mg GAE/100 g DM). In terms of oven dried pomelo byproducts, the highest TPC was retained in albedo (1337 mg GAE/100 g DW), followed by flavedo (1226 mg GAE/100 g DW), lamella (998 mg GAE/100 g DW) and pulp waste (962 mg GAE/100 g DW) respectively. Therefore, oven drying was the most suitable post-drying method to retain the bioactive compounds for pomelo byproducts. This knowledge may inspire consumer or pomelo industry operators to re-evaluate their byproducts, reduce the waste and expand the application of pomelo fruits.

Industrial relevance

Non-edible of pomelo fruits are thought as a part of waste products which generally being discarded. Interestingly, it was found that the peel have higher phenolic contents and antioxidant potentials than the pulps. However, processing involves drying process diminishes the product quality due to the deviations in quantity and feature of thermolabile phytochemicals. The objective of this work was to assess variations in total phenolic contents (TPC) and antioxidant behavior of processed pomelo peels during post drying treatments. The information reported here may encourage pomelo industry operators to re-evaluate their by-products, extending the application of pomelo fruits and reducing waste. As natural products, with apparent antioxidant capacity, processed pomelo residues look very promising for use in development of functional and nutraceutical applications.

中文翻译：

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对总酚含量和柚的抗氧化能力的干燥方法的效果（柚（L.）柚）皮

柚（Cistrus grandis（L.）Osbeck）是柑橘属的重要品种，其中含有许多对人体健康有益的营养素。柚子的不可食用部分包括flavedo，反照率，薄片和从果汁提取中获得的废物（纸浆废物）。果皮也被认为是废物的一部分，通常被丢弃。因此，本研究的目的是评估烘箱干燥（50和60°C）和冷冻干燥处理后的柚子皮中总酚含量（TPC）和抗氧化活性的变化，与新鲜柚子皮相比。与新鲜果皮相比，烤箱干燥的柚皮中TPC的TPC略有不同（4％–6％），这表明后干燥方法对保留这些天然副产物的抗氧化能力有轻微的影响。体外测定表明，与柚子副产物的整个部分中的冷冻干燥相比，涉及烤箱干燥的后干燥方法具有更高的TPC。在新鲜柚皮中发现了生物活性化合物的最高保留率（437-1876 mg GAE / 100 g DM），然后在50和60°C烘箱中干燥（892-1336 mg GAE / 100 g DM），然后冷冻干燥（555） –1267毫克GAE / 100克DM）。就烤箱干燥的柚子副产品而言，最高的TPC保留在反照率（1337 mg GAE / 100 g DW）中，其次是flavedo（1226 mg GAE / 100 g DW），薄片（998 mg GAE / 100 g DW）和纸浆分别浪费（962毫克GAE / 100克DW）。因此，烘箱干燥是保留柚子副产物生物活性化合物的最合适的后干燥方法。这些知识可能会激发消费者或柚子行业的经营者重新评估其副产品，

行业相关性

不可食用的柚子水果被认为是通常被丢弃的废物的一部分。有趣的是，发现果皮具有比果肉更高的酚含量和抗氧化能力。然而，由于热不稳定性植物化学物质的数量和特性的差异，涉及干燥过程的加工会降低产品质量。这项工作的目的是评估干燥后的柚子皮中总酚含量（TPC）和抗氧化性能的变化。此处报告的信息可能会鼓励柚子行业经营者重新评估其副产品，从而扩大柚子水果的应用范围并减少浪费。作为天然产品，具有明显的抗氧化能力，