Assessment of the inhibitory effects of sodium nitrite, nisin, potassium sorbate, and sodium lactate on Staphylococcus aureus growth and staphylococcal enterotoxin A production in cooked pork sausage using a predictive growth model

This study was conducted to analyze the effects of sodium nitrite,nisin,potassium sorbate,and sodium lactate against Staphylococcus aureus(S.aureus)growth and staphylococcal enterotoxins(SEs)production in cooked pork sausage by inoculating sausage samples containing preservative with an S.aureus strain producing staphylococcal enterotoxin A(SEA)and then storing them at 37℃ for 36 h.Samples were analyzed every 3 h to count the S.aureus colonies and to detect SEA.The modified Gompertz model was used to describe S.aureus growth in the samples under various conditions,and the preservatives with a significant antimicrobial effect were selected.In addition,the antimicrobial effects of the selected preservatives under various concentrations were tested.Results showed that sodium nitrite,nisin,and potassium sorbate had a weak effect against S.aureus growth and had no effect against SEA production,whereas sodium lactate could significantly inhibit S.aureus growth and SEA production.Moreover,the antimicrobial effect of sodium lactate was concentration-dependent,wherein sodium lactate concentration<12 g/kg showed no inhibitory effect,but when the concentration was increased to 24 g/kg,sodium lactate could effectively inhibit S.aureus growth and SEA production,and at 48 g/kg,sodium lactate had a significant inhibitory effect.

Effect of Pork Meat pH on Iron Release from Heme Molecule during Cooking

This study investigated the relationship between the level of iron chemical forms and the initial raw meat pH values during cooking, including the effect of the sodium nitrite presence. The pH value, the heme iron （HI） and non-heme iron （NHI） concentrations were measured on one ground portion of five loin, five masseter, five semimembranosus, five neck muscles and five shoulder muscles. Afterwards, all raw meats were halved and mixed with NaCl （2%）, ascorbic acid （0.05%） and 0 mg/kg of sodium nitrite （mix1） or 150 mg/kg of sodium nitrite （mix2）. Both mixes were divided into 50 g-portions, vacuum packed in cryovac bags and cooked in thermostatic bath up to F （10, 71 ℃） = 30 minutes at the core. The NHI and HI concentrations were determined both on the cooked meats and on the juice lost during cooking. The cooking process caused the release of NHl and H1 on all cooked sample juices. The HI overall percentage was significantly lower than raw meat one （P 〈 0.005） and the NHI significantly higher （P 〈 0.005） in all cooked mix 1. The raw and cooked HI percentage variances depended on the pork meat pH values （ra = 0.70）. The overall HI percentage was unchanged respect to raw meats on cooked mix 2, while the NHI amount was not quantitatively estimated. These results emphasized the role of sodium nitrite on tying up NHI in the cooked meats and safeguarding the oxidative stability of cooked meat products.