Study On The Effect Of Different Oil Storage Technology On Quality And Preservation Of Oils

China is the world's largest country in the production and consumption of edible vegetable oils.The annual consumption of edible vegetable oils exceeds 34 millio n tons,of which the consumption of flavored oils such as Luzhou peanut oil exceeds 3 million tons.In the process of edible vegetable oil production,storage and circulation,how to achieve the quality and freshness of oil products and extend the shelf life has always been a concern of the industry,and it is also a more complicated and difficult task.Because vegetable oil is affected by its own nature and storage conditions,can not avoid oxidative rancidity and quality deterioration.This paper used the soybean oil with the largest reserves in China and the peanut oil with the largest sales in the market as the experimental raw materials;conducted a more in-depth and systematic study of the correlation between storage methods and the comprehensive quality of storage vegetable oils;provided support for the development of green vegetable oil storage technologies and the preservation of oil quality;promoted the technical upgrade and product upgrade of vegetable oil storage.Designed and manufactured 8 steel oil storage tanks(the capacity of single oil storage tank were 200 kg,equipped with automatic temperature measurement and nitrogen filling equipment),of which 4 tanks stored third-grade soybean oil,another 4 tanks stored first-grade peanut oil,the storage conditions of the two vegetable oils were: static atmosphere aboveground tanks,added TBHQ aboveground tanks,nitrogen-filled aboveground tanks,and low-temperature underground tanks.The storage period is 24 months.Periodically,oil samples were taken from each oil tank to detect acid value(AV),peroxide value(PV),vitamin E and physterol contents;quantitative detection and evaluation of the volatile flavor compounds of peanut oil were conducted by headspace solid-phase microextraction-gas chromatography-mass spectrometry(SPME-GC-MS)and gas-sniffing instrument(GC-O);the effects of different storage conditions on the comprehensive quality of the two oils were studied.The results showed that the average week of annual oil storage temperature of the aboveground tanks was 19.5 ?,and the average week of annual oil storage temperature of the underground tanks was 16.8 ?.After 18 months of storage(labeled shelf life of edible vegetable oil products),the AV and PV of all oils(this is an important indicator for judging whether the quality of edible oil is qualified according to national standards)have continued to increase.The AV of the four peanut and soybean oils did not exceed the national standard limit.With PV reaching the national standard limit(6 mmol/kg for first-grade peanut oil and 9.85 mmol/kg for third-grade soybean oil),the shelf life of peanut oils: added TBHQ aboveground storage(>24 months)> underground storage(13 months)> nitrogen-filled aboveground storage(10 months)> static atmosphere aboveground storage(5 months);the shelf life of soybean oils: added TBHQ aboveground storage(>24 months)> underground storage(24 months)> nitrogen-filled aboveground storage(18 months)> static atmosphere aboveground storage(7 months).Compared with static atmosphere aboveground storage,the shelf life of peanut oil and soybean oil underground storage have been extended by 8 months and 17 months,respectively.Compared with nitrogen storage oil,the shelf life of peanut oil and soybean oil underground storage have been extended by 3 months and 6 months,respectively,and underground oil storage avoided frequent nitrogen filling operations and omited investment in nitrogen filling facilities.Although the shelf life of underground oil storage was shorter than added TBHQ oil storage,it was a safer green oil storage technology.Regardless of the oil storage technologies,the vitamin E and physterol contents continued to decrease with the increase of oil storage time,compared with static atmosphere aboveground storage,the loss rates of vitamin E and physterol in peanut oil underground storage were reduced by 13.12,9.06 percentage points,and the loss rates of vitamin E and physterol in soybean oil underground storage were reduced by 13.44,6.52 percentage points.It showed that underground storage technology played an important role in keeping the freshness of oil(taking nutritional content and nutritional quality as evaluation indexes).For Luzhou peanut oil,the change in aroma intensity and purity during storage was also an important indicator for evaluating its quality(sensory quality)preservation.The results showed that 9 kinds of 64 volatile flavor compounds were isolated and identified in the Luzhou peanut oil.Among them,pyrazines and aldehydes accounted for more than half of the total volatile flavor compounds(36.42% for pyrazines and 23.82% for aldehydes).Pyrazines were mainly 2,5-dimethylpyrazine and 2-methylpyrazine,with contents of 12.28% and 6.42%,respectively.Aldehydes were mainly phenylacetaldehyde,and the content was as high as 9.23%.These two kinds of volatile flavor compounds constituted the basic flavor of the nutty,barbecue,and sweet aromas of the Luzhou peanut oil.After the peanut oil was stored under the above 4 different conditions,static atmosphere aboveground storage,added TBHQ aboveground storage,nitrogen-filled aboveground storage,and low-temperature underground storage for 18 months.The content of pyrazines decreased from 36.42% to 16.33%,21.92%,27.02% and 29.08%,respectively.The content of phenylacetaldehyde in aldehydes decreased from 9.23% to 0.83%,0.98%,1.23% and 1.29%,respectively.The hexanal content increased to the initial value 6.40,2.08,4.37 and 2.10 times,respectively.The roasting taste,sweet aroma and overall flavor of peanut oil were significantly weakened,and the rancid taste was enhanced;TBHQ and nitrogen could effectively delay the loss of characteristic flavor compounds of peanut oil,but it was detected in peanut oil added TBHQ storage,a large number(22.55% of total volatile compounds)of oxidative decomposition products tert-butyl-p-benzoquinone and other volatile harmful compounds of TBHQ,and evaluated from the food safety aspects of oil storage,underground storage and nitrogen-filled storage oil were more scientific and green technologies.At the same time,underground storage has better flavor retention effect than nitrogen-filled storage.The above-mentioned experimental research showed that underground storage oil technology has distinct advantages,which mainly depended on the relatively constant low-temperature conditions of underground storage,but whether it was above-ground storage or underground storage,the storage temperature of oil could not be constant due to the influence of seasons and weather.So it was impossible to accurately evaluate the influence of temperature on the quality of oil during storage.To this end,three constant temperature and humidity incubators were used to conduct experimental research on the effects of different storage temperatures and different antioxidants(TBHQ,tea polyphenol,rosemary,and VE)on oil storage quality.The results showed that the temperature has a significant effect on the quality of oil during storage,the shelf life of peanut oil stored at 25 ? is 4 times that of 45 ? and 6 times that of 65 ?;the shelf life of soybean oil stored at 25 ° C is 5.1 times that of 45 ° C and 7.7 times that of 65 ?.The antioxidant effects of the four antioxidants in peanut oils and soybean oils all decreased with increasing of storage temperature.At the same temperature,different antioxidants also showed different effects,adding TBHQ has better antioxidant effect than natural antioxidants.Under different temperature conditions,the addition of antioxidants could reduce the VE loss in peanut oils;whether the antioxidants were added or not,there was a negative correlation between the stability of vitamin E and storage temperature.Adding TBHQ to delay vitamin E loss in peanut oil and soybean oil was better than natural antioxidants;physterols had good stability at room temperature and slowly oxidized under long-term storage at high temperature.Adding antioxidants(except vitamin E)could delay the oxidation of peanut and soybean oils physterols,but added vitamin E at high temperature storage would accelerate the oxidation of peanut and soybean oils physterols.Generally,a shorter and more convenient accelerated oxidation test of the oven method is used to predict the shelf life of the oil.The predicted shelf life of blank peanut oil adding TBHQ,tea polyphenol,rosemary extract,and vitamin E peanut oils were 55.7 d,229.2 d,161.6 d,161.0 d,56.5 d,and corresponding to the predicted shelf life of the soybean oils were 144 d,408 d,112 d,152 d,and 109 d,respectively.The synthetic antioxidant TBHQ has better antioxidant effects on peanut and soybean oils than natural antioxidants tea polyphenol,rosemary extract,and vitamin E.The shelf life of the accelerated oxidation test in the oven method <the shelf life obtained from the oil storage test in the incubator <the shelf life of large oil tanks aboveground<the shelf life of large oil tanks underground.In summary,in order to delay the aging of peanut and soybean oil storage quality,different oil storage technologies can be used,especially the underground natural low temperature oil storage technology(no antioxidants added and nitrogen-filled),compared with ground oil storage,the shelf life of peanut oil and soybean oil could be extended by 8 months and 17 months,and the loss of VE and sterol was reduced by 13.12 and 9.06;13.44 and 6.52 percentage points,the effect of retaining peanut oil flavor was the best;peanut oil and soybean oil were stored at different temperatures and antioxidants,low-temperature storage was conducive to their quality and safety,retaining their nutritional content.TBHQ was better than natural antioxidants in delaying the change in oil storage quality;the shelf life of the accelerated oxidation test in the oven method <the shelf life obtained from the oil storage test in the incubator <the shelf life of large oil tanks aboveground<the shelf life of large oil tanks underground.Regardless of the changes in the overall quality of the oil quality index and nutritional quality and sensory quality during storage were evaluated,the underground storage method with natural low temperature and dark protection was significantly better than added TBHQ aboveground storage and nitrogen-filled aboveground storage,of course,the effect of underground storage technology was far superior to the static atmosphere aboveground storage.