射頻處理參數應用於甘藷保存及其品質變化探討

Application of RF Processing Parameters in Sweet Potato Preservation and Its Quality Change

黃筱筑(Hsiao-Chu Huang) ； 江伯源(Po-Yuan Chiang)

《臺灣農業化學與食品科學》 57卷1期 (2019/02) Pp. 11-21

https://doi.org/10.6578/TJACFS.201902_57(1).0002

摘要

甘藷台農57號香氣、甜度皆廣受國人喜愛，但其貯存期短易發芽且易受甘薯蟻象蟲害因此貨架期短，如何建立延長儲藏期製程為市場所需之研究主題，本研究擬利用射頻加熱處理延長台農57號之貨架期。研究結果如下：利用批式射頻處理甘藷，乾式處理時，容易焦化且表面溫度分佈呈較不均勻，濕式處理可有顯著改善效果；不同電壓處理下電流、電壓大小呈正相關；不同極板間距下，乾式處理甘藷電流與極板間距呈正相關，電壓3kV下極板間距於5至15cm，電流增加0.05A，濕式處理與空白組電流呈無顯著改變；電壓5kV下於間距8至12cm下濕式處理甘藷後以加熱指數計算不同電壓及極板間距之加熱均勻度，濕式處理下電壓5kV、極板間距8cm，濕式處理甘藷呈較均匀變化，濕式加熱甘藷至30、40、50、60及70℃，高於50℃之處理組內部微細構造觀察具糊化網狀構造，低於50℃處理組則無；相較控制組L值、pH與硬度貯存時溫度低於50℃之處理無顯著差異，高於50℃之處理組呈下降；加熱至50℃之處理組於常溫下貯存30天較控制組發芽率降低74.4％；膜處理甘藷減少重量損失約3％；以DSC分析甘薯蟻象蟲卵，於47.25℃觀察到熱吸收峰，推測此溫度即可使蟲卵變性抑制卵化，綜上結果，以射頻處理甘藷至50℃可維持品質並延長甘藷之貯存時間並降低蟲害。

關鍵字

甘藷 ； 射頻 ； 甘藷蟻象 ； 貯存期

並列摘要

Sweet potato Tainung 57 (TN57) is one of the most popular varieties in Taiwan because of its aroma and sweetness. However, the shelf life of TN57 is short due to the damages of insects or pests and the sprouting. In conclusion, establishing the shelf life extended process is necessary for the market. This study intends to prolong the shelf life of TN 57 by batch radiofrequency (RF) treatment and the results are as follows. Under dry treatment, the surface temperature distribution of sweet potato was relatively uneven and coke easily. On the contrary, immerse treatment can refine the defect of dry treatment. The current and voltage are positively correlated under different treating voltage. The current is positively correlated with the electrode gap under dry treatment. Under voltage 5 kV, electrode gap 5 to 15 cm, the current was increased by 0.05 A in dry treatment. In contrast, immerse treatment and the blank remained unchanged. After immerse treatment under voltage 5 kV, electrode gap 8 to 12 cm, heating index was calculated to reveal the heating uniformity of different treatments. The index showed that under 5 kV, electrode gap 8 cm and immerse treatment, the temperature of sweet potato was relatively uniform. Sweet potato under five different temperature treatment (30, 40, 50, 60 and 70°C) were tested. The treatments with treating temperature above 50°C were observed under scanning Electron Microscopy (SEM) with a gelatinized network structure which did not exist in other treatment. Compared with the control group, L value, pH and hardness of treatments with treating temperature lower than 50°C showed no significant difference, the others showed a decrease in tendency. The 50°C treatment was stored at room temperature for 30 days and the germination rate decreased by 74.4% compared with the control group. Film treatment reduced the weight loss by about 3%. DSC analysis of sweet potato weevil eggs revealed a heat absorption peak at 47.25°C. It is speculated that the temperature can inhibit egg incubation by heat denaturation. In summary, treating sweet potato by RF to 50°C can maintain quality including extending shelf life of sweet potato and reducing damage of pests.

並列關鍵字

Sweet potato ； Radiofrequency ； Sweet potato weevil ； Shelf life