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Nutritional value and shelf life of milk and dairy products depend on the composition and stability of their constituents. The aim of the present study was to evaluate the effects of carrots as cow feed carotenoid source on butter oil fatty acid (FA) composition and oxidative stability. Milk was obtained from one trial group (TG; n=5) and one control cow group (CG; n=5) in a conventional dairy farm in Latvia. TG cows received carrots 7 kg per cow per day; the length of the supplementation period was 39 days. The stability of butter oil exposed to sunlight (3h) and held for 14 days in the temperature of 60 °C was analyzed by peroxide value method. The changes of the FA content and ratios in TG milk fat were more positive with respect to the fat nutritional value as observed in CG -- stronger increase in the content of polyunsaturated FA (p<0.05), and in the ratio between stearic and palmitic acids (p<0.05); also a tendency was seen of increasing content of short and monounsaturated FA, as well as decreasing the ratio between ω6 and ω3 FA groups. Oxidative stability of the carrot supplemented cow group's milk butter oil samples that were collected after 25- day trial period, exposed to sunlight (3h) and stored at a temperature of 60 °C was significantly (p<0.05) higher compared to CG samples. After the 39-day long trial period stability difference was not significant, despite the tendency that average polyunsaturated FA content in TG samples was higher compared to the control. [ABSTRACT FROM AUTHOR]

The quality and nutritional value of milk and dairy products are considerably influenced by the stability of its constituents. The aim of the present study was to evaluate the possibility of enhancing oxidative stability of cow's milk fat and vitamin B2 using carrots and palm oil feed supplement CAF 100 as sources of natural antioxidants in cow feed. Milk samples were collected after 25-day period of feed supplementation. The intensity of riboflavin losses during its photo oxidative degradation in sunlight was measured by the fluorometric method. A slight and significant (p<0.05) difference in higher vitamin B2 stability was seen in carrot-supplemented group (TG1) milk, where the losses of vitamin B2 were by 3.01% less compared to CG (CG). The oxidative stability of butter oil samples stored in 60 °C temperature was analyzed by peroxide value (PV) method. The oxidative stability of samples initially affected by light from both trial groups was significantly (p<0.05) higher compared to CG showing the good potential of the cow diet enrichment with carotenoid additives. The longest induction period (> 14 days) was observed in CAF-100-supplemented (TG2) cow milk fats, which can be explained by carotenoids and tocopherol presence and its possible synergism in fat protection. The induction periods of the TG1 and CG were 12.03 and 10.97 days, respectively. [ABSTRACT FROM AUTHOR]

β-Carotene (BC) and α-tocopherol in milk fat have positive implications in human nutrition, besides the specifically protecting polyunsaturated fatty acids from oxidation. To determine the possible effect on some milk components, nutritional value and lipid stability of including carrots in the diet of lactating cows, ten cows were selected in a dairy farm and divided into 2 groups (control and experimental) by 5 cows in each. In experimental group's diet additionally 7 kg carrots per cow per day were included. Individual cow milk samples were obtained 1 day before feed enrichment, in days 7, 24, 35, 42 (during the feed enrichment), and 1 week after feed enrichment. Analyses of milk fat, protein content, somatic cell count (SCC), retinol, BC, vitamin C, tocopherols, immunoglobulins (Ig), lysozyme, fatty acids (FA) were made, and milk yield was measured. Supplying cow diet with carrots showed a tendency to improve milk quality by promoting the faster decrease of SCC, and significantly (p<0.05) increasing Ig and lysozyme content, thus potentially improving milk nutritional value. The vitamin content rose significantly (p<0.05) by retinol and tocopherol contents, but β-carotene content increase in milk was not observed. Also milk fatty acid (FA) stability changes during 5 day storage in temperature of 4 - 6 °C were not observed. [ABSTRACT FROM AUTHOR]

Three spectrophotometric methods were compared for the assessment of milk fat oxidation: the AOCS (American Oil Chemists' Society) 2-thiobarbituric acid (TBA) value direct method, the TBA method of Aristova, and the modified method for the estimation of total carbonyl compounds in oils of Endo et al. Two cow milk fat samples -- a fresh fat, obtained from fresh milk, and a rancid fat, obtained from a rancid commercial butter by means of high-speed centrifugation (15.871 x g, 30 minutes at 40 °C) -- were analyzed several times in a 22-day period after sample preparation. A positive linear correlation between absorbance and storage time was established in all used methods. The method of Aristova is appropriate for exact determination of oxidation products. This method had rather good R² value (0.85) of the fresh fat sample results; however, the coefficient of variation (45.78%) showed rather large deviations between parallel analyses. The methods of AOCS and Endo et al. can be used for the assessment of the dynamics of fat oxidation by reporting absorbance values from the assay directly. By these methods rather high R² values (0.86, 0.93) of the fresh fat sample results were obtained; the coefficients of variation also were satisfactory (10.13%, 11.12%). The last two methods are cheaper and require smaller sample amounts (< 0.2 g), while the method of AOCS is the most time-consuming method. [ABSTRACT FROM AUTHOR]