عنوان مقاله [English]
Background and objectives: Nowadays, the demand for low-fat food products, such as cheese, has increased due to the increase in people's awareness about the relationship between fat and cardiovascular diseases. Therefore, the production of low-fat cheese with acceptable quality for consumers has great importance. The present study was conducted to investigate the effect of transglutaminase treatment and the addition of kappa-carrageenan gum, as a fat replacer, on the physicochemical, color and total acceptability of ultrafiltrated low-fat cheeses during 30 days cold storage (4 ◦C).
Materials and Methods: In this research, samples of ultrafiltrated low-fat cheese were produced from the retentate of ultrafiltrated milk. Milk protein concentrate powder (containing 80% protein and 0.6% fat) was used (as solution with 34% total solids) to reduce the fat content of the cheese samples and adjust the fat percentage to 8%. Kappa-carrageenan powder was used in 3 different levels (0, 0.03 and 0.06%) to produce gum-incorporated samples. After adjusting the amount of fat in the retentate and the addition of gum, the retentate was homogenized at 70 bar. After pasteurizing at 75°C for 15 seconds, the temperature of the samples was reduced to 32°C and transglutaminase was added at 2 levels (zero and 0.5 Unit/g protein). A low-fat sample, without enzyme and gum, was also produced as control sample.
Results: Based on the results, all investigated variables had a significant effect on pH, soluble nitrogen and syneresis parameters (p<0.01); While these variables, except the amount of kappa-carrageenan, had no significant effect on the moisture content (p>0.05). The pH decreased by increasing the amount of kappa-carrageenan, while the amount of this factor increased in the presence of enzyme. Also, the pH showed a decreasing trend over the time. The amount of soluble nitrogen increased by increasing the amount of kappa-carrageenan in the low-fat samples; the addition of the enzyme caused a decrease in soluble nitrogen. On the other side, the amount of soluble nitrogen showed an increasing trend over the time. The syneresis of all low-fat samples decreased by increasing the amount of kappa-carrageenan and transglutaminase. The highest percentage of syneresis was related to the control sample and the lowest percentage was related to the sample containing 0.06% kappa-carrageenan and 0.5 units of transglutaminase. Moreover, increasing the amount of gum declined the color quality of the samples, but no significant difference (in terms of brightness) was observed between the control and the samples containing 0.03% kappa-carrageenan (p>0.05). According to the results of sensory evaluation, the sample containing transglutaminase enzyme (0.5 Unit/g protein) and 0.03% gum scored as the best sample in terms of total acceptance
Conclusion: The results of this research revealed that low-fat ultrafiltrated cheese with a desirable quality can be produced by application of proper concentrations of kappa-carrageenan and transglutaminase (0.03% and 0.5 Unit/g protein, respectively).