Current situation and Development Countermeasures

2022-08-16
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Grain: current situation and Development Countermeasures of rice packaging

husk the rice to get brown rice, and then grind the brown rice to remove the peel and embryo to become rice. Because rice has lost the protection of its shell, the endosperm is directly exposed to space and is vulnerable to external factors. Therefore, compared with rice, the storage stability of rice is relatively poor, especially in the summer with high temperature and humidity, it is easier to rancidity and aging, so it is particularly important to study the packaging of rice

1. Current situation of rice packaging

1.1 basic requirements of rice packaging

the basic requirements of rice packaging are mold proof, insect proof and fresh-keeping, followed by convenient access

1. 1.1 during the processing of mould proof rice, the surface will be contaminated with bran powder, which is very vulnerable to the influence of external temperature and humidity and moisture absorption and return, which is conducive to the proliferation of microorganisms. The hygroscopic capacity of rice is related to the processing accuracy, the content of bran powder and the total amount of broken rice, especially bran powder, which has strong hygroscopic capacity and contains more microorganisms. At the same time, bran powder also contains a lot of fat, which is easy to oxidize and decompose, so that the fatty acid value increases. Mold is the most likely cause of rice mildew. At the initial stage of mildew, the rice surface turns gray and loses luster; In the process of mildew, it shows fever and emits a slight musty taste. The mold itself and the pigment produced by its metabolism will accelerate the discoloration of rice. Mildew is significantly related to water content, ambient temperature, humidity and gas composition of rice. In addition, rice's own respiratory metabolism leads to rice fever, mildew and deterioration. Therefore, the first requirement for rice packaging is mold resistance

1. 1.2 the pest of insect proof rice is mainly rice weevil, which does not lay eggs when the temperature is lower than 11 ℃ or higher than 35 ℃. The gas environment has a significant impact on pests. Wang Ruidong et al. [1] believe that CO2 can stimulate the respiration of pests, make the valve of pests open continuously, and the oxygen consumption in the body increases sharply until the oxygen is exhausted. The research shows that [2] about 17% CO2 concentration can inhibit or kill pests in three days; Controlling O2 concentration below 10%, pests can survive in dormant state; O2 concentration is less than 4%, and it will die in two weeks; The concentration of O2 is less than 2%, and the pests die within 48 hours

1. 1.3 prevent aging of aged rice during storage. The aging of rice is mainly manifested by the decrease of luster, the increase of acidity, the disappearance of rice flavor, the decrease of viscosity and the appearance of aged rice smell. Cooking quality deteriorated. Generally, aging occurs in varying degrees after one year of storage. If rice has high moisture, high temperature, low precision and more bran powder, microorganisms are easy to reproduce and age quickly, otherwise it is slow. The moisture content of rice is an important factor affecting aging. When the water content is below 12%, the bacterial reproduction is difficult, and when the water content is below 14%, it has a certain inhibitory effect on some mold spores [3]

1. 2 rice packaging materials

in the early 1990s, rice packaging was mainly made of gunny bags, cloth bags and plastic woven bags, each weighing almost more than 25kg. Although gunny bags and cloth bags are cheap and can be reused, they are difficult to achieve the purpose of long-term preservation due to their high permeability. At present, these two materials are rarely used in rice packaging. At present, plastic woven bags and composite plastic bags are commonly used

1. 2.1 plastic woven bag plastic woven bag is made of plastic film (polyethylene, polypropylene, nylon and other films) into a narrow band with a certain width, or woven from plastic flat belt with high strength and small elongation by hot stretching method. The strength of plastic woven bags is much higher than that of plastic film bags, which is not easy to deform and has good impact resistance. At the same time, due to the woven lines on the surface of woven bags, it improves the anti-skid performance and is convenient for stacking during storage. Almost all rice packages weighing more than 5kg are made of plastic woven bags

plastic woven bags are used to pack rice. The packaging method is simple, the moisture resistance and barrier of materials are poor, the rice is easy to oxidize and mildew, and the pest phenomenon is serious, especially in summer, the storage period is shorter

1. 2.2 composite plastic bags composite plastic bags are made of high barrier packaging materials EVOH, PVDC, pet, PA, PE, PP and other multi-layer plastics. This kind of packaging is better than plastic woven bag packaging in terms of moisture-proof, mold proof and insect proof effects. In addition, the pattern and trademark printing are very clear, and the text and bar code are clearly visible, which is easy to attract customers and promote sales. The vast majority of rice packages weighing less than 5kg are packed in composite plastic bags

composite plastic bags are used to pack rice, which are usually supplemented by vacuum or inflation technology and then heat sealed. Due to the compactness of the material itself and the vacuum pumping and inflation treatment, the problems of mold proof, insect proof and quality assurance on rice packaging are basically solved, which has a certain promotion and practical value. However, the compound bag packaging is easy to wrinkle when sealing and heat sealing, which will affect the aesthetics of the packaging bag. In addition, the compressive strength of composite bags is not enough, and some inflatable packaging often breaks the bag during transportation, thus affecting the shelf life of rice. In addition, the use of plastic bags is restricted due to their non degradability, difficult post-treatment, and the toxicity of plastic products

1. 3 rice packaging methods

from the perspective of packaging methods, there are basically three packaging forms, namely ordinary packaging, vacuum packaging and inflatable packaging

1. 3.1 ordinary packaging uses plastic woven bags made of polypropylene and other materials to pack rice, and uses stitches to seal. No one is imposed in the packaging process - robots, automated production lines and other intelligent devices are widely used in production. What fresh-keeping technology, this kind of packaging has a relatively poor effect on the insect prevention, mold prevention and fresh-keeping of rice, which can only accommodate grain in general. However, due to the strong tensile strength of plastic woven bags, rice with a packaging weight of more than 5kg is packaged in this way, and the shelf life is about three months

1. 3.2 vacuum packaging adopts vacuum packaging, which can reduce the O2 concentration in the storage environment, inhibit the respiratory intensity of rice and the propagation of mold, and prevent rice Chen from putting forward many valuable operable suggestions on jb/t9370 (1) 999 "changing the technical conditions of experimental machines", such as changing, mildew, insects, etc., so as to better maintain the quality of rice. At present, the vacuum degree of rice vacuum packaging is generally - 0 07~ - 0. Between 09kpa [4]. Due to the high vacuum degree, the packaging materials tightly wrap the rice, and the two ends of the rice are sharp, so the packaging bag is easy to be punctured by the rice grains, resulting in the failure of the vacuum packaging. The friction, collision and fall between bags in the circulation process of packaging bags are also easy to cause bag breakage. Therefore, the fresh-keeping packaging of rice should be combined with the circulation environment at the same time, so as to achieve good results

1. 3.3 inflatable packaging inflatable packaging is generally filled with CO2 and N2, which are colorless, odorless and non-toxic gases with relatively stable chemical properties. Rice has the ability to absorb CO2, forming a protective layer, so that rice is in a sleep state, so the changes of fatty acids, total acids, reducing sugars and viscosity are relatively small, extending the effective shelf life; Filling N2 reduces the O2 concentration in the storage environment, inhibits the growth of microorganisms in rice, and plays an important role in slowing down the change of quality. Most studies have shown that inflatable packaging can effectively maintain the quality of rice and prevent rice from mildew and insects

1. 4 evaluation index of rice

rice quality changes during storage. Through the determination of some components in rice, the quality changes can be analyzed. There are many evaluation indexes of rice. At present, the evaluation of rice quality at home and abroad focuses on sensory quality, nutritional quality and so on

1. 4.1 sensory quality of rice the sensory quality of rice can not only make people feel happy, but also affect the digestion and absorption of rice. The sensory quality of rice is identified according to gb5492 - 85, and scored according to color, smell and taste stickiness. The quality of rice is closely related to the origin, variety, cultivation, harvesting, storage, processing, cooking method and process of rice. If any link is not handled well, it will affect the sensory quality of rice

1. 4.2 changes in water content the adsorption of rice on water molecules is mainly caused by the interaction between polar groups contained in rice and water molecules. The water content on the surface of rice is mainly produced by adsorption, and the internal water content is mainly caused by the diffusion of the surface of rice to the inside, except that it is contained in the scope of the oscilloscope first. Therefore, the water content of rice has a great relationship with the environmental humidity. Measuring the water content of rice can also measure the quality of rice, and the water content is determined according to the drying method of gb5497 - 85

1. 4.3 change of fatty acids fatty acid value is one of the sensitive indicators of grain quality deterioration, and the content can be determined according to gb5510 - 85. The content of lipids in rice ranges from 0 6 %~3. 9%, and the fat content directly affects the eating quality of rice. The higher the fat, the better the gloss of rice. The aroma of rice is related to the unsaturated fatty acids contained in rice grains. The fat in rice is most prone to change, which is decomposed into glycerol and fatty acids through the catalytic action of esterase, so that the free fatty acids increase. The free fatty acids are encapsulated in the spiral structure of amylose components, making it difficult for the water required for gelatinization to pass through, and the strength of starch particles increases, causing the hardness of rice to increase. At the same time, fatty acids can also be further decomposed into low-grade aldehyde and ketone compounds, reducing the edible quality of rice

1. 4.4 change of reducing sugar rice contains a small amount of low molecular sugars, such as glucose, maltose, etc. these sugars contain free reducing groups, which will affect the reducibility of rice. The product variety and quality level of sensors and tension machine components in China are easy to be oxidized under appropriate conditions, seriously affecting the quality of rice. Compared with the rice stored at low temperature, the reducing sugar in aged rice is about 50% more, so the change of reducing sugar in rice also reflects the change of rice quality. Reducing sugar in rice is generally determined by direct titration with alkaline copper tartrate [5]

2 main problems in rice packaging

from the big gunny bag packaging in the 1990s to the small plastic packaging now, rice packaging has undoubtedly made great progress. However, there are still many problems in rice packaging from the aspects of packaging materials, packaging technology and methods and packaging structure

2. 1. The grade of rice packaging is low

as we all know, packaging plays an important role in promoting commodities. However, there is a big gap between China's rice packaging and the world's advanced countries, resulting in many problems in the circulation of rice and the lack of competitiveness to enter the international market

in terms of packaging materials, plastic bags are mostly used in China, which will bring varying degrees of environmental pollution; In foreign countries, such as Germany, most rice is packed in cartons, 500g a box. The outstanding advantages of this paper packaging are non-toxic, tasteless and pollution-free. From the perspective of packaging patterns, the design is monotonous and not novel, which is difficult to attract consumers' attention. Judging from the certification of rice, some are incomplete and lack of necessary certification. At present, there are not many marked with QS certification, green food, organic food, etc

there are many varieties of high-quality rice in China, such as Xiangzaoxian 18 in Hunan, Yangdao 4 in Zhejiang and Lujing 94-16 in Shandong. Compared with Thai fragrant rice that has entered the domestic market in recent years, the quality and variety of rice in China are not inferior. The problem is that the technology of rice storage and fresh-keeping packaging, packaging decoration and materials are backward, resulting in low-grade goods, which are difficult to enter the high-end consumer market [6]

2. 2 rice packaging technology is relatively backward

at present, ordinary packaging, inflatable or vacuum packaging are widely used in China. Due to its limited technical level, it is easy to cause packaging breakage, which brings great trouble to the sales and storage of rice. In order to achieve better packaging results, we can consider improving these technologies. The quality of foreign products is relatively good, and the semi-automatic meter of Sasaki company in Japan

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