The changes in pork quality in relation to packaging conditions during chilled storage in households

The effects of several different common packaging methods for storing fresh meat in households on the various quality characteristics of pork loin were examined during storage at 5 . These methods were: wrapping with polyethylene pouch (WP), keeping in an air-tight plastic container (CP), and using a household vacuum packaging machine (VP). The increase in the total aerobic bacteria (TPC) during storage was fastest in the WP samples, followed by the CP and VP samples. The increase in thiobarbituric acid (TBA) and volatile basic nitrogen (VBN) values over the storage period occurred most significantly in the WP samples compared to the CP and VP samples. The off-odour, tested 30 min after opening the pack, was first notable at day 15 in the CP and VP samples and at day 11 in WP samples. The colour deteriorated earlier in the WP samples than in the CP and VP samples. According to the sensory tests, WP samples were evaluated to be the worst over the storage period. Introduction Shelf life of fresh meat can be affected by some problems encountered during chilled storage, i.e. microbial growth, lipid oxidation, discoloration and increase of weep loss etc. (Hotchkiss, 1994; Lee & Yoon, 2001). In households, the left-over fresh meat from the meal should be stored in a refrigerator properly until it will be consumed again. However, in most of the current refrigerators for storing fresh meat, humidity control is poorly conducted. Therefore, by introducing an appropriate packaging, shelf life of meat can be extended by excluding the sources of additional microbial contamination and reducing evaporation during chilled storage. Most commonly, left-over fresh meat is stored in the households either by wrapping with gas permeable film or by putting in a household plastic pouch. Alternatively, meat can be kept in plastic air-tight containers, the use of which for preserving different kinds of foodstuffs and meals is, nowadays, widespread in households. More recently, the use of household vacuum packaging machines is becoming popular. Therefore, a study was carried out to compare the effects of these kinds of different common packaging methods for storing fresh meat in households on the various quality characteristics of pork loin stored at 5 . Materials and methods Both sides of loin were removed by sanitary sampling methods from five pigs, 24 h postmortem, in A grade, according to the Korean carcass classification system. pH24 values of sample meats ranged between 5.6 and 5.8. The samples were trimmed from exterior fat and cut into lengths of 6 cm, thus obtaining 38 pieces in total. The packaging methods incorporated in this experiment were as follows; (1) wrapping with household high density polyethylene pouch (WP), thickness 25 μm (Lotte Aluminum Co., Korea), keeping in an air-tight container made of polypropylene (CP) (Lock & Lock Co., Korea), and using a household vacuum packaging machine (VP) (VP-3000, Foodguard, Korea). The samples were then stored in a low temperature incubator (BI-1000M, Jeio Tech., Korea) at 5±0.5 and were allocated to each of seven intervals (0, 3, 5, 8, 11, 15, and 19 days). The TPC was determined by incubation on a Standard-I agar (Merck, Germany) at 30 for 2 days. The pH was measured using a combined glass electrode (720A, Orion, USA). Changes in the TBA were used to assess lipid oxidation (Witte et al., 1970). The VBN test using the microdiffusion technique of Conway (1958) was used to determine proteolytic degradation. A trained, 10-member sensory panel evaluated meat samples by using a 5-point hedonic scale with 0.5 intervals for discoloration and off-odour (5=none; 1=total) and outer appearance (5=extremely desirable; 1=extremely undesirable). This experiment was replicated twice and the mean values were obtained from six measurements on three separate samples at each day. All data were analyzed using Statistical Analysis System (SAS/STAT, 1988). Duncan's Multiple Range Test was used to compare means and significance which was established at P<0.05.