Prediction Of Sodium Nitrite Content In Meat And Research On The Flavor Reaction Model Systems Of Dry-cured Meat

Nitrite is commonly used in the modern process of meat products. The most important role of nitrite is to prevent the growth of Clostridium botulinum and to develop attractive cured color. However, the effect of nitrite on cured flavor is still controversial. In industry, the amount of nitrite used during meat processing largely depends on experience and is not well controlled. Thus, it is necessary to develop a strategy for predicting the content of nitrite in meat products. It is also necessary to establish model system to study the effect of nitrite on meat flavor formation.Factors affecting the nitrite content in meat products include the amount of sodium nitrite added, the storage time of product, the source of meat, and heated time. The addition of sodium erythorbate and curing time also affected the nitrite content significantly. These factors should be considered in further study of predictive models of sodium nitrite content in meat products and total heme pigment is used as a parameter for the source of meat. Predictive mathematic models of sodium nitrite content in minced meat products and dry-cured meat cut were developed. As for minced meat products without and with sodium erythorbate 500 mg/kg, they are Y=12.588+0.598X₁-0.626X₂ and Y=13.096+0.381X₁-0.363X+2 respectively, in which Y means sodium nitrite content (mg/kg), X₁ means the added amount of sodium nitrite (mg/kg), X₂ means total heme pigment (mg/kg). As for dry-cured meat, the predictive equation is: y=45.136+0.181x₁—1.306x₂⁰.342x₃, where y means sodium nitrite content (mg/kg), x₁, x₂, x₃ means the added amount of sodium nitrite (mg/kg), the curing time (d) , and total heme pigment (mg/kg) respectively. The above predicting equations could be used for the control of the content of sodium nitrite in the minced and dry-cured meat so that the color development and the content of sodium nitrite could reach the required standards.The amount of total aldehyde and hexanal in the volatile compounds from the dry cured meat made with sodium nitrite were significantly lower than those made without sodium nitrite. The reduction of hexanal generated from Fe²⁺—linoleic acid model systems indicated that sodium nitrite of 25 100 mg/kg had significant antioxidant effect on linoleic acid.The key volatile compounds obtained from the unheated reactions of D-Ribose with four amino acids (Leu, Ile, Val and Met) in acidic conditions were 3-methylbutanal; 2-Butanone, 2-methylbutanal, 2-methyl-2-butenal; 2-methylpropanal; dimethyl disulfide and 3-(methylthio)-propanal. The contents of volatile compounds in the model systems with sodium chloride or sodium nitrite were lower than those without them. Sodium chloride at a concentration of 5.8% could significantly prevent the generation of 3-methylbutanal (P<0.05). Large amount of sodium nitrite (6900 mg/kg) could significantly prevent the generation of 3-methylbutanal, 2-Butanone, dimethyl disulfide and 3-(methylthio)-propanal (P<0.05), and absolutely prevent the formation of 2-methyl-2-butenal. As for the concentration of 138 mg/kg sodium nitrite, it could significantly prevent the generation of 2-Butanone, 2-methyl-2-butenal, dimethyl disulfide and 3-(methylthio)-propanal (P<0.05). The reactiveness of amino acids with D-ribose follow the order Ile>Leu>Val.ATP, ADP, AMP, IMP, Adenosine and Inosine could not react with the four amino acids (Leu, Ile,Val, Met) to liberate volatile compounds under unheated conditions. It suggested that only ribose itself was the active flavor precursor. In fresh meat, dry cured meat of 1, 2,3 months and dry cured ham of 9, 19 months, the content of ribose (of dry matter base) were 3.28, 2.53, 3.41, 2.10, 1.02, and 0.48 mg/g respectively. These results showed that the content of ribose in dry cured meat decreased during curing and ripening, indicating that it might have some relationship with the formation of flavor compounds.