Microbial quality of fresh pork loin during storage affected by oregano oil and cranberry pulp diet supplementation in pigs

International export of fresh products means long distances and long storage periods, even up to several weeks. Pork is highly perishable and must be maintained under optimal conditions to prevent physicochemical degradation and microbiological spoilage. At the plant level, new technologies such as the use of modified atmosphere packaging, control of storage conditions and carcass pasteurization processes. Some strategies also add synthetic products to reduce physicochemical defects and microbiological spoilage in meat products. However, consumers are increasingly concerned about the quality of their food and demand more natural alternatives to the use of additives and preservatives in fresh meat (‘‘green labeling’’). The aim of this study was the supplementation of oregano oil and ground cranberry pulp added to the diets of finishing pigs to determine their antimicrobial effects on fresh loin during storage at 2±1ºC. At 8 wk of age, a total of 42 (Yorkshire x Landrace) x Duroc barrows, with an initial body weight of 25 kg, were individually allocated in pens. Six weeks before slaughter, each animal received, once a day as a top dress, 200 g of supplement made from a blend of oregano oil, ground dehydrated cranberry pulp and ground maize. Two doses of oil (250 and 500 mg/kg) and three doses of cranberry (5, 10 and 20 g/kg) were tested according to a factorial experimental design. The control group did not receive any supplements. The meat was vacuum packed and analyzed after 0, 23, 45 and 60 d. Samples were re-packaged under aerobic conditions after 0 or 23 d and analyzed after 4, 8 and 12 d.

The dietary treatments had no effect on pig growth performances (average daily gain, feeding conversion, final weight) and carcass yield compared with the control group (P<0.05). Microbial analysis was performed periodically throughout the experiment. Initial cell counts were below detection level for total aerobic mesophilic (TAM) (<10² cfu/g), Pseudomonas spp. (<10² cfu/g), presumptive lactic acid bacteria (LAB) (<10² cfu/g), and Escherichia coli and coliform counts (<10¹ cfu/g). No significant difference in TAM counts were observed between all of the six different treatments and the control group except for samples packaged at day 0 under aerobic conditions after 12 d of storage where a significant effect of the supplementation was observed (P<0.03). Under anaerobic conditions, LAB were not affected and remained the predominant microflora despite antimicrobial treatments.

It is concluded that supplementation of feed with oregano oil and ground cranberry pulp had a limited effect on the microbiological profile of the meat during cold storage. But, on the other hand, oregano oil and cranberry pulp supplemented diets do not negatively interfere with the modulation of the microflora in favour of the LAB compared with the control group.

Fortier, M. P., Saucier, L. and Guay, F. 2012. Effects on microbial quality of fresh pork loin during storage from oregano oil and cranberry pulp diet supplementation in pigs. Can. J. Anim. Sci. 92: 465-471. doi:10.4141/CJAS2012-078