Effects Of Low Sodium Composite Salt On The Eating Quality Of Dry-Cured Duck

Dry-cured duck, also known as "salted duck" or "dried duck", is one of the Chinese traditional cured meat products. Dry-cured duck is easy to be processed as it just requires to be marinated and dried under natural conditions. Due to its characteristics of unique flavor, dry-cured duck is well favourble with consumers. However, Chinese traditional dry-cured duck always has high content of sodium chloride, and excessive sodium intaking will initiate problems such as high blood pressure or cardiovascular diseases according to the previous researches. Therefore, it is very important and necessary to develop the low salt dry-cured meat products with lower salt content.Firstly, this experiment was performed to study the effects of partial replacement of sodium chloride by using potassium chloride, calcium chloride and calcium lactate on the physicochemical properties and sensory quality of dry-cured duck. Base on the single factor tests for potassium chloride, calcium chloride, and calcium lactate, the Box-Behnken response surface methodology was applied to optimize the percentages of the replacement. And the best replacement ratio of sodium chloride by composite salt was determined. Finally, the effects of sodium chloride partially replaced by low sodium composite salt on the protein, fat, and flavor compound of dry-cured duck was studied. Detailed research contents and results are as follows:1 Effects of replacement of sodium chloride by potassium chloride, calcium chloride and calcium lactate on physicochemical properties and sensory quality of dry-cured duckThe effects of sodium chloride partially replaced by potassium chloride, calcium chloride and calcium lactate on moisture content, color, textural properties and sensory quality of dry-cured duck have studied. The results showed that, the mass fraction of sodium chloride is 10% in the control group. With 25%,10%and 15% molar substitution of sodium chloride by potassium chloride, calcium chloride and calcium lactate respectively, we got the best suitable alternative when we were considered all the factors.2 The response surface optimization test of sodium chloride partly replaced by low sodium composite saltThe Box-Behnken response surface methodology was applied to optimize the percentages of the replacement, and two quadratic polynomial mathematical models about textural properties and sensory quality were established. The results showed that, in the potassium chloride single factor experiment, with the substitution increasing, potassium chloride addition had a markedly negative effect on the taste (P<0.05) but had no significant effect on the texture of the products (P>0.05). The highest substitution percentage was 25. In the calcium chloride single factor experiment, calcium chloride addition had a significant effect on the hardness and chewiness (P<0.05) but not the spring of products (P>0.05). While it had a significant effect on the sensory attributes of texture, aroma, taste, bitterness, and overall acceptability but not saltiness (P<0.05) and the highest substitution percentage of the calcium chloride was 10. In the single factor experiment of calcium lactate, it had a significant effect on the texture of hardness and chewiness and sensory evaluation of aroma, taste, saltiness, odor, and overall acceptability (P<0.05), but no significant effect on the spring or the texture (P<0.05). The substitution percentage of 15 of calcium lactate was the best suitable. The response surface model, with potassium chloride, calcium chloride, and calcium lactate as independent variables and textural properties and sensory quality as responses, was highly fitted (R1/2=0.9572;R2/2=0.9845). The textural properties of the dry-cured duck was significantly influenced by calcium chloride, calcium lactate, and calcium chloride × calcium lactate (P<0.01). While the sensory quality of the dry-cured duck was significantly influenced by potassium chloride, calcium chloride, calcium lactate, calcium chloride × calcium lactate (P<0.01), and calcium chloride × calcium lactate (P<0.05). Thus, the maximum replacement percentages of the sodium chloride by potassium chloride, calcium chloride, and calcium lactate were 21.30%, 11.93% and 11.12%, respectively. Compared with the control group, the chewiness was almost not changed, and overall acceptability was decreased slightly (but in the acceptable range) in the verification test. The relative error of chewiness and overall acceptability compared with the predicted value were 2.07% and 11.12%, respectively. Under such conditions, the concentration of sodium chloride being added to the dry-cured duck was decreased by 44.45% without changing the major eating attributes of the products.3 Effects of sodium chloride replaced by low sodium composite salt on protein, fat and flavor substance of dry-cured duckThe effects of sodium chloride partially replaced by low sodium chloride on the total nitrogen, non-protein nitrogen, proteolysis index, free amino acid, TBARs and flavor have been studied. The results showed that, compared with the control group, the total nitrogen, non-protein nitrogen and proteolysis index had been decreased slightly in the low sodium group. But the difference was not significant (P>0.05). The content of Leu and Arg were significantly higher than the control group in drying 40h (P<0.05). At the end of drying, the content of Ser and Arg was significantly higher than those in the control group (P<0.05). The content of Asp and Glu which had umami properties and the content of Gly, Ala and Ser which had sweet properties was not significantly difference compared with the control group(P>0.05). Other free amino acids had the same results. At the end of drying, compared with control group, TBARs value was slightly up regulated, but the difference was not significant (.P>0.05). All free fatty acids but linolenic acid were not significantly different compared with the control group (P>0.05). SPME-GC-MS was used to analysis the volatile components in low salt duck. The volatile components were mainly composed of hydrocarbons, alcohols, aldehydes, ketones, esters and other compounds. It had 49 kinds of flavor components. The content of hexanal and 3-hydroxy-2-butanone was significant higher than the control group>0.05). These substances have important contributions to the flavor of the dry-cured duck. It was proved that composite salt was beneficial to the formation of the flavor.