Research on process parameter optimization and process intelligent control is an important element in the design and development of grain drying equipment. Existing methods mostly use simulation, device experiments or field experiments to obtain data, which have large differences with the actual drying results or the experimental process is time-consuming and vulnerable to interference. In this study, with reference to the process and structure of large continuous grain drying production equipment, a continuous grain drying simulation experimental system was developed and designed, including grain feeding equipment, dryer main body, grain discharge equipment, waste heat recovery, condensing device, hot air equipment and measurement and control system, which can simulate the grain drying operation process. This system can also optimize the drying process parameters, and carry out indoor grain drying quality change law, energy consumption law and production efficiency. The system can be used as the first-line staff post. The system could be used as the pre-service training for the workers on the production line, the experimental teaching of related majors in universities and colleges and the experimental research system of scientific research institutions.

介绍了响应面分析法及其适用性,应用该分析方法以谷物中不饱和脂肪酸的提取率为响应值,设计了一个四因素五水平实验,探究微波萃取反应条件中萃取温度、萃取时间、料液比和丙酮占比各因素对提取率的影响,并将得到的最优化实验条件应用于本科生实验课程教学.响应面分析法引入到大学化学实验中,能够有效地优化既有实验的反应条件,降低实验成本;也有利于学生了解实验设计的概念,形成科学的实验设计思维.

The content of unsaturated fatty acid (UFA) is an important index to evaluate the quality of corn. It is not only the main fatty acid of corn, but also a very important dietary fatty acid and essential nutrient in human body. In order to study the relationship between UFA content and the drying system coupling factor of corn, an orthogonal experiment was designed. This experiment was based on the actual drying parameters of the corn dryer in Harbin grain dryer. First, the drying process was divided into three stages, each stage had different hot air temperature and relative humidity, so as to establish a six factors and three levels of sectional temperature and humidity orthogonal drying experiment. There were a total of 30 groups of experiments. Then, the content of UFA in dry corn was determined by microwave extraction and gas chromatography. Finally, the relationship between drying system coupling factor and UFA content in corn was calculated. On the premise of meeting the drying standard of edible corn, the highest content of UFA was 6.553% under the drying conditions of hot air temperature of 35 oC-50 oC-50 oC and relative humidity of 30%-45%-30%.After repeated verification, the actual optimal value was 6.547%. It is proved that the actual optimal value was consistent with the predicted value through the verification of the predicted optimal combination. Then the coupling relationship between UFA and coupling factors of the drying system ( including accumulated temperature, the absolute water potential sum of the air, the absolute water potential sum of the grain, the difference between the absolute water potential sum of the air and the absolute water potential sum of the grain, the accumulated of the absolute water potential of the air, the accumulated of the absolute water potential of the grain, the difference between the accumulated of the absolute water potential of the air and the accumulated of the absolute water potential of the grain) were calculated, and the results showed that the order of coupling relationship between UFA content and drying system was as follows: STMMG (0.674 3)> DSTMMGA (0.660 2)> STMMA (0.608 9)> SGT (0.589 3)> DATMMGA (0.477 2)> ATMMA (0.315 7)> ATMMG (0.257 6)> EAT (0.203 8). The coupling relationship between UFA content and absolute water potential of grain was the best. The formula for calculating the absolute water potential of grain can explain the coupling degree between them, and also prove that the theory of water potential can analyze and predict the content of unsaturated fatty acids in corn grains.

In 2015, the Ministry of Agriculture of the People's Republic of China formally put forward the strategy of using potatoes as the staple food. Potato is one of the most productive crops in China. However, fresh potato is easy to go moldy in storage. Fatty acid is an important component for quality of food. Most of the fatty acid in potato is unsaturated fatty acid which is the necessary nutrient of the human body and has an important physiological function. In this research, we have conducted an orthogonal experiment to determine extraction temperature, extraction time, the proportion of acetone and the solid-liquid ratio for microwave-assisted extraction of unsaturated fatty acid from raw potato flours. The content of unsaturated fatty acid in each group of experiment was tested by the gas chromatographic method. After all the data were acquired, the microwave-assisted extraction process of the unsaturated fatty acid in the raw potato flours was optimized by virtue of Design-Expert 8.05 Analysis and Response Surface Method. Then the optimized program was used for studying the influence of the hot air drying temperature on the content of unsaturated fatty acid of potato. The results allowed us to develop the extraction model (P=0.000 1<0.01,R2=0.939 8) of unsaturated fatty acids in raw potato flours . By use of the model, the optimum extraction technology of unsaturated fatty acids in raw potato flours was obtained and they were, the extraction temperature was 81 ℃, the extraction time was 11 min, the volume ratio of acetone in the extraction solvent was 0.802 5, and the solid-liquid ratio was 3.25:1. The effects of various factors on the content of the unsaturated fatty acids were as follows: the volume ratio of acetone > the solid-liquid ratio > the extraction temperature > the extraction time, and the predicted value of the content of unsaturated fatty acid in the raw potato flours was 1.084 mg/mL. After getting the average value from three replicated tests for the optimal extraction process, the actual value of the content of the unsaturated fatty acid in the raw potato flours was 1.081 mg/g, which confirmed the predicted response value. In the application of optimization scheme, the drying of raw potato flours was operated by making use of different temperature (50, 60, 70, 80 and 90 ℃ ), and the determination showed that, with the increase of the drying temperature, the content of total unsaturated fatty acids had been increased (P<0.05), therein, the content of linoleic acids had also been increased significantly (P < 0.05), and the content of oleic acids and linolenic acids had been also increased, which has been not increased significantly by comparing with the content of linoleic acids. Such change can be attributed to two reasons: on the one hand, the lipolysis had produced the glycerol and fatty acid, on the other hand, the fatty acid has constantly been biosynthesized. Through the research on the influence of hot air drying temperature on the quality of raw potato flours, the optimal hot air drying temperature was obtained according to the index of content of unsaturated fatty acid to realize the optimal quality of raw potato flours after drying so as to promote the strategy of taking potato as the staple food.

In early 2015, Ministry of Agriculture put forward the strategy that potato is classified as the fourth staple food and transferred into popular principal food suitable for dietary habit in China. Even though the China's potato production ranks the first in the world, the sustainable development of potato processing and consuming is still extremely restricted due to the following reasons: The percentage of potato deep processing remains low; the processing products of potato are single, and have low nutrition and add value; and the potato products as staple food suitable for our dietary habit are in lack. Potato flour is one of prime products in potato deep-processing, and hot air drying has been widely used in the drying for agricultural products because of its easy operation, low cost and simple requirements for environment, court and equipment. The potato gelatinization characteristics affect the reproducibility of dehydrated products of potato. The more highly gelatinized the potato, the worse the reprocessing property, and the more difficult the application of potato as China's principle cooking food. Therefore, it has an important significance to the research of the effects of the hot air drying conditions on the gelatinization characteristics, the drying technology of dehydrated potato products and China's strategy of potato as staple food. Based on thin-layer drying experiment, the paper researched the influence of different temperature (40, 50, 60, 70, 80, and 90℃), different air velocity (0.5, 1.0, 1.5, 2.5 and 3.5 m/s) and different dicing length of fresh-cut potato (2.5, 5, 10 and 15 mm) on potato flour gelatinization quality. Microstructure and gelatinization quality of potato flour were analyzed with the use of scanning electron microscopy (SEM) and differential scanning calorimeter, and the water-absorbing capacity was measured. The results showed that gelatinization enthalpy could represent the degree of potato gelatinization; the lower the gelatinization enthalpy, the lower the degree of gelatinization; the range of initial gelatinization temperature was 62.31-64.96℃, and the range of termination temperature was 70.16-74.19℃, which was higher than the gelatinization temperature of pure starch product; the starch was not completely gelatinized when drying under the temperature higher than gelatinization temperature; the samples dried under the air velocity of 0.5-2.5 m/s showed no significant difference in gelatinization enthalpy (P>0.05), while the gelatinization enthalpy of the samples dried under the air velocity of 3.5 m/s was significantly smaller than that under other air velocities; the enthalpy of potato flour decreased significantly with the increase in dicing length (P<0.05); ungelatinized samples showed no significant difference in water-absorbing capacity, and water-absorbing capacity was strengthened as the degree of gelatinization got higher; the gelatinization degree of potato dehydrated products was low when the hot air drying was under the temperature of 70℃, the air velocity of 1.0 m/s and the cutting length of 10 mm. This research can provide theoretical basis for the production of ungelatinized potato flours with hot air drying method.

Potato, which is widely regarded as a total nutrient food, is the fourth major food crop after wheat, corn and rice in the world. In the same time, potato is one of the most highly productive food crops in China with potentiality of further development in the future and has been widely used in the food, feedstuffs and pharmaceutical industry. So it has also been endowed with the properties of both food crops and commercial crops. The preservation techniques in China, the largest potato producer, are so lagging that the loss amount is estimated to be over 15% each year, which is far above that of developed countries in Europe and America. The potato drying process is an important step as it plays a crucial role in reducing the moisture of agricultural products, extending the storage period and improving the additional values. As the most extensive method among all artificial drying processes, hot air drying has the properties of easy manipulation, low cost, and fewer demands for the environment, space and equipment. Research on the property of hot air drying, development of drying models and determination of water transfer parameters has great importance to the effectiveness in predicting, regulating and optimizing of the drying process. In this paper, the drying curves, the material temperature, the moisture effective diffusivity velocity and the activation energy are discussed at the different hot-air temperature, air velocity and dice length based on the thin layer drying experiments. The hot air temperatures are taken as 40, 50, 60, 70, 80 and 90℃. The air velocities are 0.5, 1.0, 1.5, 2.5 and 3.5 m/s. The potato dices have the cross section of 10 mm × 10 mm, and the lengths are classed as 2.5, 5, 10 and 15 mm. The main results are as follows. The hot air drying of fresh diced potatoes has typical characteristics of the Weibull distribution with the falling rate. The process can be divided into 2 phases, i.e. the stage at first increase phase and then the deceleration phase. The drying time is shortened with the rising of the hot air temperature and the decreasing of the dice length, and the air velocity has a little effect on the time except the early stages when the increasing air velocity can give the promotion of drying rate. The hot-air drying process of fresh diced potatoes obeys the Weibull function, and the value ofR2 ranges from 0.991 to 0.999, which means the hot-air drying process is in good agreement with the Weibull distribution function. The scale parameter in the model grows with the increase of hot-air temperature and air velocity, and decreases with the rise of dice length. The shape parameter in the model has positive correlation with the dice length and air velocity, while air temperature causes little impact on the shape parameter. The moisture effective diffusivity velocity, which is between 1.859×10-9 and 12.509×10-9 m2/s, is significantly (P<0.05)correlated to the hot-air temperature and air velocity, but the dice length is not significantly (P>0.05). The geometric dimension parameter is relevant to the dice length and air velocity, which increases with the rise of air velocity and dice length). The activation energy of hot-air potato drying is found to be 19.107 kJ/mol, which is lower than the average activation energy of diced or chipped fruit and vegetable, and thus hot-air potato drying is easier to accomplish. This research will help to provide theoretical and technical foundation to the hot-air drying of the fresh diced potato.

利用酶水解法和酶比色法2种方法来检测马铃薯自由淀粉的含量[1],结果表明与传统的酶水解法相比,酶比色法利用多个函数拟合的方法能够科学的计算出标准工作曲线,更加准确、合理,并且在测量结果基本一致的前提下大大缩短了时间.