油茶籽储藏品质变化规律及条件优化

    Change rule of storage quality and optimization of storage condition for Camellia oleifera seeds

    • 摘要: 为探讨不同储藏条件下油茶籽品质的变化规律及其原因,找出适宜的储藏条件,该文分别以物料含水率、空气相对湿度和储藏温度为单因素,研究油茶籽储藏过程中的含油率、酸值、过氧化值等品质的变化规律及相应的脂肪酶、脂氧合酶活性,并对微生物的生长情况进行统计分析。运用响应面法,综合考察上述因素对油茶籽品质的影响。结果表明:油茶籽的储藏过程存在3至4个月的后熟期,酸值、过氧化值均随含水率、温度和储藏时间的增加而升高。脂肪酶及微生物的繁殖与酸值的关系比较显著。优化的油茶籽储藏工艺参数为:空气相对湿度57.6%~67.4%,储藏温度17.2~20.4 ℃,物料含水率8.9%~10.4%和储藏时间62.2~110.3 d。该研究可为油茶籽储藏及后续加工提高出油率和保障品质提供技术支持。

       

      Abstract: Abstract: Camellia oleifera seed, commonly known as the oil-seed camellia seed or oil-tea camellia seed, just like oil palm, olive and coconut, is one of the most prominent woody edible oilseeds. Camellia oleifera seed oil, one of the favorite cooking oil used wildly in China's southern provinces and Southeast Asia, has much in common with olive oil in chemical composition drawing great attention from the public, with high amounts of oleic acids (76.1%-83.3%) and linoleic acid (7.0%-11.03%) and was often titled as "Eastern Olive Oil". However, it is not easy to store the seeds because of the high total amount of unsaturated fatty acids up to 90% and high temperature and high humidity climate in Camellia oleifera seed producing area, which are tend to lead to the quality degradation during storage. In order to maintain good storage quality, the effects of storage conditions on quality of Camellia oleifera seeds and the reasons for them were explored in this study. Using moisture content of material (7%, 8.5%, 10%, 11.5%, 13%), air relative humidity (50%, 60%, 70, 80%) and storage temperature (4, 15, 20, 25℃) as single factors, the change in oil content, acid value and peroxide value of Camellia oleifera seeds were determined during the 8-months storage. At the same time, the lipase activity, lipoxygenase activity and the growth of microorganisms, which were highly related to the increases of acid value and peroxide value, were also investigated during storage. The change trend of oil content showed an increase in the beginning and decreased after the peak, indicating that there was a phenomenon of post-ripening observed during the storage. In this study, the post-ripening period of stored Camellia oleifera seeds was 3-4 months, which was similar to the post-ripening period of 2-3 months for peanut and was obviously longer than the post-ripening period of 10-20 days for corn. The acid value and peroxide value were increased with the increase of moisture content of material, storage temperature and storage time. The significantly positive correlation between the lipase activity and the acid value indicated that the increase for acid value of Camellia oleifera seeds during storage was mainly due to the accumulation of free fatty acids produced by hydrolysis of fat resulting from lipase. Within 6-months storage, only a few of molds of Camellia oleifera seeds were observed. However, once microorganisms grew in large quantities with the prolongation of storage time, lipase would be produced to further promote the increase of acid value. In addition, based on the above results, the effects of moisture content of material, air relative humidity, storage temperature and storage time on oil content, acid value and peroxide value were investigated using response surface method. The regression equation predicting quality variation was established and it proposed that suitable air relative humidity and storage temperature can promote the post-ripening of Camellia oleifera seeds during storage. The comprehensive optimization ranges of Camellia oleifera seed storage parameters, obtained using frequency analysis method from the regression analysis of standardized comprehensive score values, were as follows: air relative humidity of 57.6%-67.4%, temperature of 17.2℃-20.4℃, moisture content of 8.9%-10.4%, storage time of 62.2d-110.3d. Under the optimal conditions, the comprehensive qualities of Camellia oleifera seed oil are good. In order to make the best of post-ripening effect and improve the storage quality, it is suggested that in practical operation, air relative humidity of the storage during post-ripening period should be 1%-2% higher than the storage after the post-ripening stage, and the temperature should be 1℃-2℃ higher. This study can provide support for storage and the subsequent oil processing of Camellia oleifera seeds to improve the oil production rate and guarantee the quality.

       

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