Quality Changes Of Beef Granules (Dog Food) During Drying And Storage Process

With the improvement of living standards in China and the arrival of the aging society, the petfood industry bears great potential for development. Nowadays, the development of the pet foodindustry in China is very fast, but there is almost no research on pet food, and less enterprisetechnological innovation and low technical ability either, all of these hindered the development ofthe pet food industry seriously. We chose the pet food （dog food） produced by Jixian GuaYueLvFaPet Products Factory on this project to research（Hereinafter referred to as beef granules）, thenutrition content of the product was studied to make it meet the needs of pets and provide a reliablebasis for the finalization of the formulation of the product, drying characteristics during dryingprocess and use low-field NMR to study the changes of water characteristics, as well as storagestability of the products in25℃and37℃storage conditions. What we have done providedtheoretical and practical help for enterprises. The results were as follows:1. Determination of nutrition of pet food. The pet food were processed by two ways: one usedminced beef, flour, starch, beef liver, beef bone mud, glycerol and so on as the main materials, afterblending with other ingredients, stretching, cooking, cutting, drying, cooling then packed. Anotherwas use the same main materials and auxiliary material but less water, after extruding, sprayinggrease and natamycin, cooling then packed. The content of basic nutrition of moisture, protein, fatand ash and mineral elements content of Ca, Mg, Fe, Zn, Cu and Mn of different batches of aproduct were detected. According to this improved the formula of the product continuously to makethe nutrition of the product follow up with the AAFCO standard requirements finally.2. Low field-NMR in measuring water mobility and distribution. After cooking the moisturecontent of half-finished beef granules was40.48%. After drying the moisture content fell to21%.The results of drying characteristics and changes of water distribution at different dryingtemperature and drying powers were as follows: drying can reduce beef granules moisture contentand microwave drying rate significantly higher than the hot air drying. Drying also resulted in theAw drop（P <0.05）and TPA （Texture Profile Analyse） change. Hardness and chewiness increased（P <0.05）while springness and cohesiveness decreased（P <0.05）during hot air drying process.Microwave drying has the same change trend but has lower hardness and better springness.Considering drying quality and efficiency, hot air drying should be selected dried at50℃for90min, the moisture content of dried product was21.44%, Aw value was0.671, hardness andelasticity were5571.04g and0.793respectively; microwave drying should be chosen dried at680Wfor90s, the moisture content of the product was20.87%, Aw value was0.696, the hardness and springness were3468.32g and0.878after drying.The T₂relaxation test results showed that in the drying process, immobilized water wasconverted into bound water and free water. The relaxation time of transformed bound water wasincreased which means the association degree decreased than the original one. The bound waterproportion is the largest when drying at50℃compared to40and60℃, the largest bound waterproportion when using microwave drying is680W. MRI results showed that the loss rate of theouter layer water in the beef granules is higher the loss rate of the inner water during hot-air dryingprocess, but during microwave drying process, the two rates is equivalent.3. The quality changes of different packaging at destructive test and validation test were asfollows: Deoxidizer can inhibit the growth of mold and fat oxidation obviously, products withoutdeoxidizer become mildewed within30days when stored at25℃conditions, which means thenecessary of deoxidizer. Packaging material had shown significant difference in moisture content,Aw and TPA（P <0.05）.The KOP coextruded film packaging have the significantly higher moisturecontent, minimum hardness and chewiness and the highest springness（P <0.05）. The impact ofpackaging materials on the organization was no difference. The KOP coextruded film can bestmaintain the original odor of the product, while the other two kinds had no difference. Thedifference of TBARS value of EVOH coextrusion film and PA/PE film was not significant（P <0.05）, while the KOP coextrusion film storaged at25℃could significantly inhibit fat oxidation（P <0.05）, when stored at37℃only significantly lower than the other after75d（P <0.05）.The mold number of KOP coextrusion film during the whole storage period was <50cfu/g whilethe other two kinds of packing were>50cfu/g. From a security point of view only KOPcoextrusion film can meet the storage requirements and the ability to maintain product quality wasbest. When packaging should choose KOP coextrusion film or high barrier property of packagingmaterial which has lower moisture permeability and oxygen permeability than the KOP coextrusionfilm and cooperate with the deoxidizer at the same time.