Effect of vacuum packaging at room temperature on maintaining storage quality of millet

Abstract：Millet is the product of the husk removal of Foxtail Millet, one of the oldest crops in the world, which originated inthe Yellow River basin, and now widely planted in the northern region of China. Millet serves as a kind of common coarsecereals, and natural health-care product, which can be used both as food and medicine,attracting a large amount of consumers.However, the storage of millet become challenge because the millet easy to change without the protection of shell. In thestorage process, the millet can be disturbed by many parameters, including temperature, humidity, oxygen and microorganism,to deteriorate product quality, such as aging, fever, mildew, insect damage, etc. Therefore, it is necessary to explore theeffective methods forthe millet storage and preservation, in order to ensure the stability of millet quality and food security.This study aims to investigate some effects of vacuum packaging on the storage quality of the millet. In this experiment, Jingu42 millet was used as the test material. The test millet was packed in 0.08mm thick polyamidecomposite polyethylene bags,each containing 400g. Samples were randomly divided into three groups. The first group of millet was sealed with vacuum(absolute vacuum is 0.01MPa) for storage. The second group of millet was conventional closed storage. The third group ofmillet was conventional storage as the control condition. All samples were stored at room temperature. Taking a bag of milletevery 30 days to measure the relevant indicators, such as the crude fat, free fatty acid, lipoxygenase (LOX) activity, watercontent, yellow pigment, color difference and texture,5 times in total（150 days）.The results showed that compared with theconventional storage, the vacuum packaging storage can effectively inhibit lipoxygenase activity(P<0.05), delay the oxidativedecomposition of millet lipid(P<0.05), reduce the levels of the free fatty acids in millet(P<0.05), better maintain milletmoisture(P<0.05), reduce millet yellow pigment loss(P<0.05), better keep the brightness(P<0.05), beige(P<0.05), elasticity(P<0.05) and adhesion(P<0.05), of the millet. Isolation of air and reduction of oxygen during storage can effectively delay theaging of millet, and maintain the taste of millet. At room temperature, the storage effect of millet is betterthan beforein the0.08 mm thick polyamide composite polyethylene bag under conventional closed storage, but not as good as the vacuumpackaging. The storage effect of the conventional storagewas the worst. The reason for this phenomenon can be related to theoxygen content in the storage environment under different packaging methods. The quality of millet was easily deteriorated bythe conventional packaging storage, because the millet was in full contact with the air,if the storage environment was rich inoxygen. The oxygen content in the environment was relatively fixed under the condition of conventional closed storage, whilewith the consumption of millet itself, the oxygen content was less and less, which can inhibit the oxidation of millet lipid to acertain extent (P<0.05), slow down the loss of yellow pigment, and delay the aging of millet.Under the vacuum packing mode,most of the oxygen in the storage environment was pumped out to the outside, and the oxygen content in the storageenvironment was greatly reduced, which effectively insulated the contact between millet and oxygen, so the vacuum packingeffectively delayed the quality deterioration of millet. The storage of millet in vacuum packaging at room temperature cankeep good storage quality. The results of this study have a promising practical significance for guiding the storage of milletand improving millet quality. This finding canalso provide a theoretical basis for the promotion and application of vacuumstorage technology in grain production.