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The effects of selected organic acids and salts on microbial numbers, pH, exudate, and color were studied for vacuum-packaged, fresh pork chops. Pork chops were dipped for 2 min in (vhr) 1% acetic acid, 1% acetic/l% lactic acid, 1.5% acetic/l.5% sodium acetate, 3% acetic/ 3% sodium ascorbate, 3% acetic/2% NaCl or sterile, distilled water before being vacuum-packaged and stored at 2" -4°C for 6 weeks. Treatments containing 3% acetic acid resulted in lower aerobic microbial numbers (PcO.05) and effectively inhibited Enrerobacferiaceae. Treatments containing 1% acetic acid, with or without 1% lactic acid, were ineffective.All acid treatments increased exudate and were detrimental to meat color (PcO.05) although sodium ascorbate reduced color damage. Chops treated with 3% acetic acid/3% sodiuti ascorbate had the highest Hunter a and L color scores.

Effects of 3.0-kGy irradiation on microflora and other attributes of fresh, vacuum-packaged pork loins were examined during storage (2-4"C, 98 days) and mishandling (24-2X, 24 and 48 hr). Shelf life of pork chops from irradiated loins was determined at 5°C. Irradiated loins kept at 2-4"C tested negative for Salmonella spp., Campylobacter spp., Clostridium perjkingens and Staphylococcus aureus. Yersinia spp. was detected in pork chops held at 5°C; this organism, C. perfringens and Aeromonas spp. were present in abused samples. In two irradiated samples Listeria monocytogenes was found. Irradiation reduced aerobic, anaerobic and Aeromonos spp. counts; lactobacilli were least affected. Chemical spoilage began after 91 days at 2-4°C. With irradiation, TBA values were unaffected but Hunter a color values increased.

Pure cultures of Salmonella typhimurium, Pseudomonas aeruginosa, Staphylococcus aureus and two lactic starters were plated with laboratory media containing 0.5% of a food grade poly-or pyrophosphate. Heated or unheated tetra sodium pyrophosphate (TSPP) was highly inhibitory or lethal to all cultures tested, followed by unheated sodium tripolyphosphate (STPP) and sodium polyphosphate glassy (SPG), while sodium acid pyrophosphate (SAPP) was not inhibitory or enhanced recoveries. Heating reduced the effectiveness of phsophates as inhibitors.

Survival and growth of naturally occurring or inoculated bacteria were studied in refrigerated (5"C), vacuum-packaged ground pork irradiated at 100 krad (1kGy). Numbers of naturally occurring mesophiles, psycbrotrophs and anaerobes or facultative anaerobes were reduced (PCO.01) by irradiation, whereas lactic acid bacteria were least affected. Partial bacterial recovery during subsequent storage at 5°C suggested sublethal bacterial injury due to irradiation. Irradiation prolonged shelf-life 2.5-3.5 days (3@44%) in uninoculated and l&1.5 days in inoculated (lo5 CFU/g) meat. Added sodium acid pyrophosphate (SAPP) (0.4%) contributed two additional days to inoculated, irradiated pork shelf-life but had no effect on the naturally occurring micrbflora. Lipid oxidation did not increase (P>O.O5) due to irradiation and was unaffected by phosphates.

Microbiological and some physical and chemical effects of treating pork chop surfaces with sodium acid pyrophosphate, a commercial phosphate blend, potassium sorbate and phosphate/sorbate/sodium acetate solutions, with or without sodium chloride, before packaging were studied in pork chops vacuum-packaged and stored at 2A"C for 10 weeks. All treatments containing potassium sorbate reduced (P

A calorimetric method developed for determining p,g levels of soluble orthophosphates in soils was successfully used in cooked and uncooked pork to monitor hydrolysis and residual levels of added sodium acid pyrophosphate (SAPP). The method is based on the formation of blue color by reacting existing orthophosphate with molybdate ions in an acid medium and preventing further reaction by rapidly sequestering excess, unreacted molybdenum ions with a citrate-arsenite reagent. The usefulness of the method to monitor poly-and pyrophosphate hydrolysis in meat is discussed.

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