Study On Conditioning And Preservation Technology Of Pork And Its Adaptability To Normal Temperature Logistics

As a new type of meat products,the prepared pork products are mainly processed with technology including food additive treatment,molding,and so on.These products are safe,convenient and nutritive,and have attracted a lot of attentions.But,the shelf lives of the products are usually short because of the microorganism growth caused spoilage,hindering the development of the related industry.The exploitation of control technology based on microorganism growth inhibition,to prolong the shelf lives,is an effective method for solving this industrial problem.The ‘Internet plus’ business model is spring up rapidly in China with an increasing number of online consumer.Electronic business effectively promotes the development of fresh food industry.At present,the quality control of fresh product is challenged due to the imperfect cold-chain logistics system for the products.The quality control of fresh product under normal temperature logistics is rarely reported.This work studied the combined technology of quality control for prepared pork meat(PPM),and investigated the effects of logistics factors on the technology to obtain the optimized parameters.The main research contents and results are as follows.(1)Optimizing the gas mixture ratio of modified atmosphere packaging(MAP)for PPM by simplex-centroid design.Based on the design,total bacteria count,total volatile basic nitrogen(TVB-N)value,pH value and sensory score were used as indices to evaluate the effect of gas mixture ratio(O2,CO2 and N2)on chilled meat.Compared with the control group of pallet packing,a fitting mixture of gases could obviously inhibit bacterial growth,reduce TVB-N production and maintain sensory quality.The indices showed significant correlations with each other(p < 0.01).Total bacteria count,TVB-N value and their weighted value measured at 8th day and 10 th day were selected to establish six regression mathematical models with three factors including O2 percentage,CO2 percentage and N2 percentage,followed by optimizing the gas mixture ratio independently.The optimum gas ratio was confirmed to be 22% O2 and 78% CO2 after comparative investigation on the preservation effects on PPM.Under this condition,the total bacteria count and TVB-N value of PPM kept at 8th day was respectively 5.85 lg(cfu/g)and 14.00 mg/100 g,and the shelf life comparing with that of pallet packing extended for 5 days.(2)Screening the preservatives of PPM followed by formulation optimization.According of <Standards of using food additives>,8 preservatives can be used in prepared meats,in which ε-PL,tea polyphenol and nisin showed relative stronger inhibition on pseudomonas.Their diameters of inhibition zone at the dose of 50 mg/m L were 52.51±0.51 mm,50.20±0.86 mm and 49.14±2.64 mm,respectively.The optimized working concentration of preservatives in our previous work was adopted,i.e.0.5 g/100 mL.Based on simplex-centroid design,the effects of preservative formulation on the storage quality of MAP-PPM were investigated.Compared with the control group,all the formulation could obviously inhibit bacterial growth,reduce TVB-N production and maintain sensory quality.Total bacteria count,TVB-N value and sensory score analyzed at 9th day and 12 th day were selected to establish six regression mathematical models with three factors including ε-PL percentage,tea polyphenol percentage and nisin percentage.The optimum formulation was confirmed to be 100% ε-PL after comparative investigation on the preservation effects on MAP-PPM.Meanwhile,it was implied that all the preservatives had no synergistic effect with each other.Meanwhile,it was implied that al the preservatives had no synergistic effect with each other.After treatment with ε-PL,the total bacteria count and TVB-N value of MAP-PPM kept at 9th day was respectively 5.99 lg(cfu/g)and 13.72 mg/100 g,and the shelf life comparing with that of control group extended for 2 days.(3)Evaluation and optimization of preservation technology of PPM in normal temperature logistics.The effects of absorbent paper,ambient temperature and vibration time on the storage quality of MAP-ε-PL-prepared pork meat were investigated.Absorbent paper could obviously inhibit bacterial growth,reduce TVB-N production and maintain sensory quality by absorbing the juice outflowed from PPM during the chilling storage.The effect of quality improvement positively associated with using numbers of the paper,but there was no significant difference between number 2 3(p > 0.05).The quality worsening of MAP-PPM at normal temperature could be slowed down by placing in a polystyrene foam box containing ice packs for the control of microclimate temperature.The shelf life gradually reduces with the increased normal temperature from 8℃ to 38℃,and obviously prolonged with the increased number of ice packs.The shelf life of MAP-PPM co-packed with 2 ice packs extended 7 days at the normal temperature of 18℃,compared with that packed without ice pack.The long time logistics vibration could increase the total bacteria count and TVB-N value of MAP-PPM during cold storage compared with the control,and the increases were significantly promoted after more than 18 h vibration.The synthetical preservation technology of PPM,composed of preservative treatment,MAP with 2 absorbent papers and polystyrene foam box packing with 2 ice packs,was carried out in normal temperature logistics.Compared with the non-transported control,both turn-around transportation inside and outside Wuhan city at normal temperature(8~15℃)could significantly impact on the total bacteria count,TVB-N production,drip loss,sensory quality,pH and texture,and the transportation outside city shortened the shelf life of PPM for 2 days.The results indicate that the storage quality of PPM after normal temperature logistics can be effectively maintained by the technology based on preservative treatment,MAP,microenvironment adjustment and transportation time limitation.However,to promote the industrialized application of this technology,the standards of packing microenvironment and transportation time responding to the quality control at different normal temperatures need to be further investigated.