The Study Of Different Pre-cooling,Packaging And Storage Methods On The Carbon Footprint And Food Quality Of Cooked Rice From The Perspective Of Unit Operations

Global warming is a global issue,and the methods to reduce the amounts of greenhouse gases(GHGs)emissions are carried out by many countries.Since the food system produces large amounts of GHGs,its carbon footprint(CF)arouses widespread concern.Therefore,it is meaningful to develop CF measurement and classification methods for food processes.Food production process is combined with many unit operations,sothe effects of different pre-cooling methods,packaging methods and storage methods on the CF and food quality of products were investigated,in order to simple the whole life cycle assessment.The pre-cooling methods were included refrigerator cooling,air blast cooling,vacuum cooling.The packaging methods were included vacuum packaging,air packaging and modified air packaging.The storage methods were included refrigerator storage and light incubator storage.The results of this research are shown in the following.Firstly,the results showed that the final CF of cooling 200 g cooked rice were 54.36±1.07 gCO2 eq,66.05±2.00 gCO2 eq,741.55±27.26 gCO2 eq,1914.10±141.24 gCO2 eq,2463.61±221.21 gCO2 eq,and 3916.54±202.28 gCO2 eq,under conditions of refrigerator cooling at 0 °C and 8 °C,vacuum cooling,and air blast cooling at 0 °C,3 °C and 8 °C,respectively.The carbon emissions from electricity consumption contributed to the vast majority of the final CF for product during cooling process.Secondly,the effects of different pre-cooling methods on the quality of cooked rice were investigated.Compared with other cooling methods,the refrigerator pre-cooling time was significantly increased(p<0.05).In addition,the effects of different pre-cooling methods on the water loss of cooked rice were investigated.Compared with traditional cooling methods,the water loss rate of cooked rice was increased significantly under vacuum cooling method(p<0.05).With the storage time increasing,whiteness and the hardness of the cooled rice increased.In addition,the pH value and the springiness decreased while the storage time increasing.There was no significant effect of different pre-cooling methods on rice whiteness and pH value(p>0.05).Thirdly,the results showed that the final CF of packaging 200 g cooked rice were 22.27±0.01 gCO2 eq,57.94±0.01 gCO2 eq,106.82±0.13 gCO2 eq,112.15±0.33 gCO2 eq,117.60±0.19 gCO2 eq and 122.71±0.19 gCO2 eq under conditions of vacuum packaging,air packaging and modified air packaging(40%O2+20%CO2+40%N2,50%O2+20%CO2+30%N2,60%O2+20%CO2+20%N2,70%O2+20%CO2+10%N2),respectively.The carbon emissions from plastic consumption contributed to the majority of the final CF for product during packaging process.Besides,for modified air packaging,gas consumption contributed some of the final CF.Fourthly,the effects of different packaging methods on the quality of cooked rice were investigated.During the short period of storage,with the storage time increasing,the whiteness and the hardness of cooked rice increased,while the springiness of cooked rice decreased.The results show that there was no significant effect of different packaging methods on quality change of cooked rice(p>0.05).Fifthly,the effects of different storage methods on the quality of cooked rice were investigated.During the storage period,the whiteness and the hardness of the cooled rice increased correspondingly with the storage time increasing,respectively.When the storage temperature increasing,the whiteness and hardness decreased,the springiness increased and the storage time decreased.There was no significant effect of different storage methods on quality change of cooked rice(p>0.05).Fifthly,cooked rice could storage 3,2 and 1 day under 0 oC,4 oC and 10 oC,respectively.So the final CF ofstorage 200 g cooked rice were 358.29±0.72 gCO2 eq,217.81±0.84 gCO2 eq,134.56±0.45 gCO2 eq,1134.14±3.02 gCO2 eq and 475.1±3.52 gCO2 eq under conditions of refrigerator storage(0 oC,4 oC and 10 oC)and light incubator(4 oC and 10 oC),respectively.The storage time was decreased with the temperature increasing.Thus the final CF of storage was decreased.The final CF of refrigerator storage was decreased significantly compared to the other storage method(p<0.05).The consumption of electricity contributed a lot of final storage CF.Finally,taking quality of cooked rice,cooling CF,cooling time and weight loss of cooled rice into account,the result showed that the refrigerator cooling at 0 oC was the optimistic cooling method.Taking quality of cooked rice and final CF of packaging and storage into account,the results showed that the vacuum packaging and refrigerator storage at 4 oC were the optimistic packaging and storage methods,respectively.