INFLUENCE OF CONTROLLED MICROBIAL CURING ON PORCINE MUSCLE

SUMMARY— A previously developed technique was adopted to study the influence of certain microbiological populations and their effects on processed meat. The technique consisted of an initial reduction of surface bacteria on conventionally handled muscle tissue via a hot water dip, followed by processing at 28° C in a sterile plastic isolator where Pediococcus cerevisiae was introduced into the curing solution. This treatment was compared to reduced initial count and conventional samples. Identification of the bacteria in the curing solution of each treatment indicated that a Lactobacillus spp. was predominant in the reduced initial count treatment. The inoculated Podiococcus cerevisiae was predominant in the reduced initial count inoculated treatment white Staphylococcus epidermidis and Flavobacterium diffusum were predominant in the conventional treatment depending upon the trial. Tenderness and bacterial load were significantly (P < .01) increased by treatment while pH was significantly (P < .01) decreased. Oxidation and muscle composition were not affected by treatment. Samples from all treatments were acceptable organoleptically.     

INFLUENCE OF BACTERIA ON THE CARBONYL COMPOUNDS OF GROUND PORCINE MUSCLE

Quantitative data were obtained for total carbonyls, total monocarbonyls, methyl ketones, saturated aldehydes, 2-enals and 2,4dienals from fresh, reduced surface flora (Dip) and inoculated muscle samples incubated at the optimal growth temperature of the respective bacteria. Individual monocarbonyl compounds were identified by thin-layer and gas liquid chromatography. Micrococcus cryophilus, Pseudomonas fluorescens and Staphylococcus aureus decreased total carbonyls by 57, 18 and 43%, respectively, and total monocarbonyls by 53, 20 and 33%, respectively. Pediococcus cerevisiae increased the total carbonyl and total monocarbonyl content by 70 and 71%. Concentrations of carbonyls in the control samples were directly related to temperature of incubation. Methyl ketones, saturated aldehydes, 2-enals and 2,4dienals were decreased by M. cryophilus, Ps. fluorescens and S. aureus but each monocarbonyl class was increased by P. cerevisiae.     

EFFECT OF A PORCINE PANCREATIC COLLAGENASE ON MUSCLE CONNECTIVE TISSUE

SUMMARY– Porcine and bovine pancreas as well as porcine spleen, liver and kidney were analyzed for possible collagenolytic activity. Both the porcine and bovine pancreas extracts possessed collagenolytic activity at pH 5.5 and 37°C. The ability of the pancreas extract to break down connective tissue was not due to tryptic or chymotryptic activity, but was due to a combination of collagenolytic and elastolytic activity. The collagenase was partially purified using Sephadex chromatography and was shown to degrade collagen into small soluble peptide fragments.     

TENDERNESS OF PRERIGOR STRETCHED PORCINE LONGISSIMUS MUSCLE

Bone and connective tissues at the 14th thoracic vertebra of one randomly selected side of each of six pork carcasses were cut 90 min postmortem by the Tendercut^TMprocedure, while companion sides served as controls. Carcasses were suspended from the hock tendon and chilled for 24 h. The Longissimus muscle (LM) was removed between the 9th thoracic and 4th lumbar vertebra and divided into three equal sections (locations 1, 2, 3; anterior to posterior) to determine the effect of Tendercut on Warner-Bratzler and Lee-Kramer peak force, sarcomere length, fat and moisture content. Tendercut resulted in lower (P < 0.05) Warner-Bratzler peak force, Lee-Kramer peak force and total energy in all locations within the LM. The average decrease was 14.2% for Warner-Bratzler peak, force and 14.5% and 16.2% for Lee-Kramer peak force and total energy, respectively. The Tendercut treatment also resulted in longer (P < 0.05) sarcomere lengths in all locations within the LM, with an average increase of 19%.     

INITIAL POSTMORTEM PORCINE MUSCLE PH EFFECT ON HEAT-INDUCED GELATION PROPERTIES

Heat-induced gelation properties of the semimembranous muscle from induced DFD (dark, firm and dry) and normal pigs were characterized to evaluate the effect of muscle pH on strength and cooking loss of gels induced by a heating at 0.7C/min. The pH of muscle slurries (10% protein with 2% Nacl) were adjusted to 5.5, 6.0, 6.5, or 7.0 with 1 M 2-[N-Morpholino] ethanesulfonic acid buffer. Muscle with a high initial pH (DFD) had lower cooking losses at all adjusted pHs. Force required to penetrate the gel (Pf), force required to move plunger through the gel (Fp), and viscosity index of the gel were consistently higher for DFD muscle at each adjusted pH except pH 5.5. These results indicate that ultimate pH influences the thermal gelation properties of a meat product if the pH is ≥ 6.0. DFD muscle had desirable protein functionality and cooking yield.     

MODE OF ACTION OF ETHYLENE OXIDE ON SPORES OF Clostridium botulinum 62A

SUMMARY— Death of spores of Clostridium botulinum when exposed to gaseous ethylene oxide followed first order kinetics. Supplementation of a synthetic medium with the purine and pyrimidine bases of DNA and RNA indicated, as judged by outgrowth from spores which had received sublethal ETO treatments, that the lethal action of ETO on the spores was through alkylation of the guanine and adenine components of DNA. Observed impairment of RNA and protein synthesis was considered an indirect effect resulting from alkylation of DNA components; however, additional evidence bearing on this point is needed to support a more definite conclusion.     

EFFECTS OF FOUR SPECIES OF BACTERIA ON PORCINE MUSCLE. 1. Protein Solubility and Emulsifying Capacity

SUMMARY– A technique was used to obtain aseptic porcine muscle, portions of which were inoculated with cultures of Pediococcus cerevisiae, Micrococcus luteus, Leuconostoc mesenteroides and Pseudomonas fragi. The inoculated samples were compared with aseptic controls throughout a 20-day storage period at temperatures of 2 and 10°C. All 4 organisms grew at 10°C, but only P. fragi and L. mesenteroides grew at 2°C. The solubilities of the various protein fractions were affected by inoculation treatment. This was exemplified by correlation coefficients ranging from —.37—0.50. The coefficients indicated the interrelationships affected by storage conditions and bacterial growth. Protein solubility studies revealed a loss in the water-soluble fraction during storage of the controls and the M. luteus- and L. mesenteroides- treated samples. Samples inoculated with P. fragi evidenced an initial loss, followed by an increase. The solubility of meat proteins in a salt solution increased during the first 8 days of storage, then decreased or remained relatively constant for all samples. In comparison with controls, samples inoculated with P. fragi increased in salt-soluble protein solubility during the first 8 days, whereas those inoculated with L. mesenteroides decreased during the latter part of storage. Insoluble protein generally increased except for P. fragi- inoculated samples, which decreased. Nonprotein nitrogen (NPN) increased for all treatments and controls during the 20-day storage period. NPN extracted from the samples inoculated with P. fragi increased greatly. The pH increased with growth of M. luteus and P. fragi and decreased with growth of P. cerevisiae and L. mesenteroides. The emulsifying capacity was not influenced by the growth of M. luteus or P. cerevisiae. However, the emulsifying capacity of samples inoculated with L. mesenteroides decreased, whereas that of samples inoculated with P. fragi increased.