title: Relationships between ultimate pH and microbial, chemical, and physical characteristics of vacuum-packaged pork loins.
abstract: This study evaluated the effect of ultimate pH (pHu) of pork on shelf life based upon microbial growth, drip loss, and oxidative rancidity (2-thiobarbituric acid [TBA] procedure) in vacuum-packaged loins stored at 4 degrees C. Glucose and lactate concentrations of the pork loins were also measured. Thirty-six pork loins (pH = 5.56 to 6.57) were collected at a commercial slaughter facility 1-d postslaughter. All pigs were from the same genetic line. Loins were grouped by pH (group: pH range): A: 5.55 to 5.70, B: 5.71 to 5.85, C: 5.86 to 6.00, D: 6.01 to 6.15, and E: > 6.16. They were analyzed at days 0, 6, 14, 24, and 34. For aerobic plate counts, groups A and B were significantly lower than C through E, while psychrotrophic or Enterobacteriaceae counts of groups A and A through C were significantly lower than groups B through E and D and E, respectively. Lactic acid bacteria counts were not significantly influenced by pHu. Group A had higher glucose concentrations than groups C through E and higher lactate concentrations than groups D through E on most sampling days. Group A had a higher TBA value than group E at days 0 and 34. Group A displayed greater drip loss than groups D and E at day 6 and groups B through D on days 24 and 34. Based on the microbial and drip loss results, a pork loin pHu of 5.8 to 5.9 appears to be optimum to provide a vacuum-packaged shelf life of at least 24 d with minimum drip loss.
authors.affiliation: Department of Food Science and Technology, University of Tennessee, 2605 River Drive, Knoxville, TN 37996-4591, USA.
authors.forename: B L
authors.initials: BL
authors.lastname: Knox
authors.forename: R L J M
authors.initials: RL
authors.lastname: van Laack
authors.forename: P M
authors.initials: PM
authors.lastname: Davidson
mesh_terms: D000818:Animals; D001420:Bacteria, Aerobic / Q000254:growth & development; D015169:Colony Count, Microbial; D003258:Consumer Behavior; D003257:Consumer Product Safety; D004755:Enterobacteriaceae / Q000254:growth & development; D005516:Food Microbiology; D018857:Food Packaging / Q000379:methods*; D005519:Food Preservation / Q000379:methods*; D005947:Glucose / Q000032:analysis; D006801:Humans; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000032:analysis; D007778:Lactobacillus / Q000254:growth & development; D015227:Lipid Peroxidation; D008460:Meat / Q000382:microbiology* / Q000592:standards*; D011786:Quality Control; D013552:Swine; D013649:Taste; D013696:Temperature; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis; D013997:Time Factors; D014618:Vacuum
chemical_list: D017392:Thiobarbituric Acid Reactive Substances; D019344:Lactic Acid; D005947:Glucose