Grape contains varieties of nutrients and bioactive components that may benefit the health of human body. Its dried products, raisins, are traditionally made by hot air drying, but the waxy texture of its skin would be a barrier to moisture removal, significantly prolong the drying time, and cause the heat sensitive nutrients degraded due to long exposure to elevated temperature. Cold atmospheric plasma is an emerging non-thermal processing technology that may be used in many food applications. Plasma contains large amount of ionized gas molecules that are highly energetic to rapidly etch the material surface. In this sense, cold plasma is capable of being applied as a pretreatment for drying process. In this study, we aim to develop novel use of cold atmospheric plasma as drying pretreatment and to investigate the effect on the quality result of raisins to preserve the nutrients and bioactive components. Grapes were pretreated with cold atmospheric plasma before subjecting to hot air circulating oven at 70°C for final drying. To confirm surface morphology changed by plasma processing, scanning electron microscope and Fourier transform infrared spectrometer were used for observation and functional group characterization, respectively. Color value and phenolic content were also monitored as the quality control of processed grapes. The results showed that the drying time of plasma pretreated group was about 25% shorter than that of control group when grapes were treated using 200 watts power for 10 times at distance between nozzle and grapes of 1 cm. Micro-fission was observed on the surface of plasma treated samples while giving a lighter color to final product. Moreover, the vitamin C and phenolic content of plasma pretreated raisin was significantly higher than the control group. To sum up, plasma pretreatment could be an effective method for decreasing drying time and preserving the nutrients during drying of grapes. The investigation on optimizing processing parameters is critical for the development of such technology for future.

Effect on the quality of raisin dried with cold atmospheric plasma pretreatment: Microstructure, total phenolic content, antioxidant activity, and color

256th National Meeting (2018)

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