Abstract
Elevation of acid degree values (ADV) and peroxide value (POV) indicates deterioration of nutritional and sensory qualities of dairy products during storage. Iron fortification in bovine milk cheeses in relation to lipolytic parameters and their correlations have been studied, while no such studies have been reported on caprine milk cheeses. The objectives of this study were to evaluate levels of ADV and POV of iron fortified [regular ferrous sulfate (RFS) and large microencapsulated ferrous sulfate (LMFS)] goat milk Cheddar cheeses compared to those of non-fortified control cheese (CC) and their correlations. Three batches of 3 types (CC, RFS and LMFS added) of goat milk cheeses were manufactured and stored at two temperatures (4°C and -18°C) for 0, 2 and 4 months. Iron was supplemented to RFS and LMFS cheeses by 8.23 g and 9.03 g per 9 kg, respectively. ADV and POV were determined using standard methods of examining dairy products (Richardson, 1985) and AOCS (1975) procedures. Results showed that ADV values for CC, RFS and LMFS cheeses for 0 and 4 month storage at 4°C were: 0.67, 0.73, 0.64; 1.24, 1.78, 1.58, respectively, indicating significant (P < 0.05) elevations occurred in ADV for all three cheeses during 4 months storage. The cheese samples at 4 months storage showed significantly (P < 0.05) higher peroxide values compared to 0 and 2 month stored ones. The samples stored at refrigeration temperature (4°C) revealed slightly more lipid oxidation than those stored at frozen temperature (-18°C). Significant (P < 0.05) elevations in POV for all goat cheeses stored for 4 months and slight increases in POV at higher temperature implies that the longer time and higher temperature storage can elevate the rate of lipid oxidation in goat milk Cheddar cheeses. Correlations (r) between ADV and POV for the pooled data of three types of the caprine cheeses across storage periods were significant (P < 0.01), while r values of CC cheeses alone were negative. It was concluded that significant correlations exist between extents of lipolysis and lipid oxidation in the caprine milk Cheddar cheeses during 4 months storage.
Highlights
Quality of dairy products has been evaluated by various analytical methods
The objectives of this study were to: 1) determine acid degree value (ADV) and peroxide value (POV) of control and iron fortified caprine milk cheeses stored at two temperatures (4 ̊C and −18 ̊C) for 0, 2 and 4 months, and 2) evaluate correlation coefficients between acid degree values (ADV) and POV of the experimental goat cheeses in relation to the extents of lipolysis and lipid oxidation of the products
The outcomes of the present study revealed that the ADVs had significant positive correlations with the POVs of the three types of goat Cheddar cheeses stored both 4 ̊C and −18 ̊C for 4 months storage period
Summary
Lipolysis is the hydrolysis of lipids catalyzed by lipase enzymes, which has been a major dairy industry problem due to its implication of rancid flavor defect in milk, cheese and other dairy products [1]. Flavor deterioration resulted from lipolysis of dairy products has caused serious industry problems in storage stability and consumer acceptability [2] [3]. Lipolysis and proteolysis are two major processes in dairy products ripening controlled by a variety of chemical, physical, microbiological, textural and rheological changes which take place under controlled environmental conditions [1] [4] [5] [6] [7] [8]
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