Study On The Quality Characteristics Of Different Varieties Of Pork And Quality Grading Of Lean Meat Pork

The formulation of pork quality grading standards lays the foundation for a better pork market in China in terms of quality and price.Compared with foreign countries,pork grading started relatively late in China.The current quality grading standard traces back to the Industrial Pork Grading Standards revised respectively in 2009 and 2012.With the improvement of breeding quality,some major changes have taken place on pig carcasses.And therefore previous standards to an extent do not cater to the conditions of current pig carcasses.In the meantime,China has gradually formed a unique segmented meat consumption market,and the demand for segmented meat grading standards is particularly prominent.Based on this,the thesis analyzes the differences in pork quality characteristics among different local breeds and lean pig to establish a pork quality grading model suitable for China's national conditions.Moreover,the thesis aims at building up the pork belly grading photograph with Chinese characteristics.The research findings can provide a theoretical basis for the formulation of China's pork quality grading standards.The main results are as follows:(1)Taking the purebred Northeast Min Pig,Ba Min Black Pig,Beijing Black Pig and Wuzhishan Pig as the research objects,the differences of pork quality characteristics of different breeds were analyzed.The results showed that there were significant differences in water holding capacity,tenderness,pH,intramuscular fat,protein and water content of lean meat pigs and local pig breeds(P<0.05),and for the four local pig loins in 1 h after slaughter,the pH value was higher than that of lean meat pigs.Furthermore the shear force values of the loin of purebred Northeast Min Pigs and Ba Min Black Pigs were significantly lower than that of lean meat pigs(P<0.01),and the tenderness was better;the intramuscular fat and protein content of the outer loin of the Northeast Min Pig and the Ba Min Black Pig were significantly higher than those of the lean meat pigs(P<0.05).These results can provide a certain theoretical basis for the establishment of quality grading standards for lean meat pigs.(2)Taking lean carcass pig as the research object,the study aimes to establish a pig carcass grading model.In this study,data on 316 carcass of lean meat pigs were collected,and the results showed that the carcass weight range after slaughtering acid was 57.70?106.80 kg;the lean meat rate range was 44.22?63.35%,5?6 ribs and 5?6 lumbar eye muscle area was 26.00?66.00 cm~2 and 23.00?76.00 cm~2 respectively;the maximum average backfat thickness was the neck-chest junction,where the maximum backfat thickness reached 61.25 mm;the minimum average backfat thickness was 11?12 ribs,and the smallest thickness of the back fat reached 13.51mm.The thickness of the back fat gradually decreased from the head to the tail,that is,the junction of the neck and chest to the 5?6 lumbar vertebrae,and increased slightly at the last rib(fourteenth rib).The collected data were statistically analyzed by principal component regression,establishing a commercial pig carcass yield prediction model as:lean meat rate(%)=0.745+0.006×6?7 rib back fat thickness-0.006×carcass weight+0.002×the rib eye muscle area model of 5-6,R~2=0.842.Combined with the index of backfat thickness,carcass weight and other indicators,the carcass grade was comprehensively evaluated,and the commercial swine grade was divided into four levels from grade 1 to grade4.(3)Pork belly is a characteristic part preferred by residents in China,and yet there is currently no quality grading standard for pork belly.Based on the collected data for 125 lean meat commodity pork belly as the research object,and with the use of computer vision technology,the study used MATLAB to process photos for the lean meat and fat meat in the pork belly cross section to extract the lean meat proportion and lean meat characteristic parameters such as the number of layers,the area of lean meat,the thickness of subcutaneous fat,the evenness of lean meat,etc.to study the grading standards of pork belly.The results showed that the proportion of lean meat,the number of lean meat layers,the number of lean meat areas were significantly negatively correlated with the sensory evaluation level(P<0.01),and the thickness of subcutaneous fat,the uniformity of lean meat were extremely significantly positively correlated with the sensory evaluation level(P<0.01).The grading prediction equation of pork belly was constructed as:y=1.434+3.445×lean uniformity -0.288×lean area number,R~2=0.859,and according to the characteristic parameters combined with the image acquisition,a five-level grading photograph of pork belly from level 1 to level 5 was constructed to achieve the rapid identification of pork belly.