| Halloumi cheese can be used as a good ingredient for grilled foods due to its special anti-melting property.Salt plays an essential role in the taste and preservation of cheese.However,numerous studies have noted that high salt or sodium intakes have close relation with hypertension which is the most substantial risk factor for cardiovascular disease.Reducing salt content has become an important challenge for all food producers.Currently,Halloumi cheese has not been introduced into the China,so there is a lack of research on its production process parameters.The optimization of Halloumi's production process parameters will lay a foundation for the industrial production of Halloumi cheese in China and the exploration of effects of cooking and low-salt storage on the quality of Halloumi cheese will provide references for the improvement of functional quality and storage method of Halloumi cheese.In this study,the yield,physicochemical,texture and sensory qualities of cheese under different process parameters were determined.Results revealed that increasing the proportion of goat milk in raw milk caused an increase in the yield,protein content,hardness and chewiness of Halloumi cheese.However,due to the high price and unpleasant astringency of goat milk,cow's milk was a better choice to be used as raw material for the later experiments.By envaluating the effects of pasteurization method,calcium chloride and squeeze pressure on the yield,physicochemical composition,texture and sensory quality of Halloumi cheese,the optimal process parameters were determined as follows: the pasteurization method was 65 ?,30 min,the addition of calcium chloride was 0.015%,and the pressing method was a stepwise pressure(cheeses were treated at 0.2 MPa for 20 minutes and then treated at 0.6 MPa for 40 minutes).Effects of cooking temperature(0°C,65°C,80°C,95°C)on the functional quality of Halloumi cheese were investigated.Results showed that the protein and calcium content were significantly increased and the surface structure was more flat in cooked cheeses.Fourier infrared spectroscopy analysis indicated that cooking could greatly promote the hydrophobic interaction between casein structures and thus lead to rearrangement of casein secondary structure.Results of the melting value and DSC thermal analysis proved that the anti-melting property of cheese cooked at high temperature could be greatly enhanced compared with the control group.The p H4.6-SN/TN,12% TCA-SN/TN,5% PTA-SN/TN and free amino acids content in cooked cheeses were much lower indicating that the degree of proteolysis was significantly reduced after cooking.The color value results demonstrated that cooking at high temperature caused reduced brightness while increased yellowness.The analysis of volatile components in cheese by GC-MS showed that the content of alcohols,ketones and acids in the hot-melt cheese decreased,while the content of ketones,aldehydes and esters increased.Based on the comprehensive texture and sensory quality,95°C was determined as the best cooking temperature to form the functional quality of Halloumi cheese.Effect of salt reduction on Halloumi cheese was investigated throughout 4 weeks of storage.Protein,moisture,sodium,salt-in-moisture ratio,p H,and lactic acid were analyzed for their physicochemical composition.Proteolysis was evaluated by nitrogen fractionation.A texture analyzer was used to determine the textural properties.Microbiological analyses included yeasts and molds and lactic acid bacteria.The sensory analysis was conducted by a 30-member panel.Results revealed that salt reduction had a significant effect on moisture,sodium,salt-in-moisture ratio,lactic acid,and p H of the cheese.Levels of p H4.6 SN,TCA SN,PTA SN and free amino acids increased significantly during storage,moreover,no significant difference was found between salt treatments until the level of salt reduction reached 40%.Hardness and chewiness were apparently lower in low-salt cheeses than that in high-salt cheeses,whereas meltability showed the opposite trend which increased significantly with the reduction of sodium concentration.In addition,the mean counts of yeasts and molds and lactic acid bacteria decreased significantly during storage.Sensory analysis revealed salt treatments had a great effect on texture and flavor in the late two weeks.Performances of high-salt cheeses generally outweighed the low-salt cheese,while cheese salted with 6% sodium brine was the most preferable at the end of 4 weeks of storage.Taking 6% Na Cl-salted cheese as a control group,effects of partial substitution of Na Cl by KCl on the storage quality within four weeks were measured.The moisture content,p H value and counts of lactic acid bacteria in KCl-substituted group were much higher while hardness and chewiness were much lower.In the later stage of storage,significant sourness and bitterness appeared in 2/3 KCl-substituted group,and the total scores of the 1/3 KCl-substituted group and the 1/2 KCl-substituted group were significantly higher than that of the 2/3 KCl-substituted group. |
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