Comparative appraisal of ghee and common vegetable oils for spectral characteristics in FT-MIR reflectance spectroscopy.

FT-MIR spectra of ghee (anhydrous milk fat) and common vegetable oils were acquired using HATR in 4000-650 cm-1 region. The differences in absorbance by carbon-hydrogen (C-H) stretch in fatty acid chain at 3.48 µm and absorbance by carbonyl (C-O) stretch of ester linkage at 5.7 µm in ghee and that in vegetable oils were studied. The clear differences in the spectra of ghee and that of the vegetable oils were noticed in fingerprint region, which can be very well utilized to develop FT-MIR spectroscopy as a promising tool to detect presence of common vegetable oils mixed in the ghee as an adulterant.

Comparison of Surti goat milk with cow and buffalo milk for physicochemical characteristics, selected processing-related parameters and activity of selected enzymes.

AIM: The study was undertaken to find out the physicochemical characteristics, selected processing-related parameters and activity of selected enzymes in Surti goat milk. MATERIALS AND METHODS: Milk samples from Surti goats and buffalo milk samples were collected during the period from July 2013 to January 2014 at Reproductive Biology Research Unit, Anand Agricultural University (AAU), Anand. Milk samples from Kankrej cows were collected from Livestock Research Station, AAU, Anand. Samples were analyzed for physicochemical characteristics such as acidity, viscosity, surface tension, specific gravity, refractive index, freezing point, and electrical conductivity. Samples were also analyzed for selected processing-related parameters such as heat coagulation time (HCT), rennet coagulation time (RCT), rate of acid production by starter culture, alcohol stability, and activity of selected enzymes such as alkaline phosphatase activity, catalase activity, proteolytic activity, and lipase activity. RESULTS: Goat milk had the highest acidity, viscosity and surface tension, followed by cow milk and buffalo milk. However, the differences in acidity, specific gravity, surface tension, refractive index, electrical conductivity, HCT and lipase activity of three types of milk studied, viz., goat, cow, and buffalo milk were found statistically non-significant (p<0.05). The buffalo milk had the highest specific gravity, followed by those found in cow and goat milk. The viscosity, freezing point and RCT of goat milk was significantly lower (p>0.05) than that of the buffalo milk. However, the difference in viscosity, freezing point and RCT of goat milk and that of the cow milk was statistically non-significant. The cow milk had the highest refractive index, followed by goat and buffalo milk. The cow milk had the highest proteolytic activity and heat coagulation time (HCT), followed by those found in buffalo and goat milk. The goat milk had the lowest freezing point, lipase activity, and RCT, followed by those found in cow and buffalo milk. The goat milk had the highest electrical conductivity, followed by those found in buffalo and cow milk. The collected goat, cow and buffalo milk samples showed negative stability at 68% (v/v) alcohol concentration. Goat milk showed positive alcohol test at 75% (v/v) alcohol concentration. Acidity was found to increase proportionally with time. After 14 h, it was found that goat milk became thicker, but the curd had a very low consistency. Cow milk had the highest alkaline phosphatase activity and catalase activity followed by those found in goat milk and lowest alkaline phosphatase activity and catalase activity was found in buffalo milk. The alkaline phosphatase activity and proteolytic activity of goat milk was significantly lower (p>0.05) than that of the cow milk. However, the difference in alkaline phosphatase activity and proteolytic activity of goat milk and that of the buffalo milk was statistically non-significant. Alkaline phosphatase activity of buffalo milk was significantly lower (p>0.05) than that of the alkaline phosphatase activity in cow milk. CONCLUSION: It can be concluded from the study that the goat milk has highest acidity, viscosity, electrical conductivity, and surface tension compared to that of cow and buffalo milk. The goat milk has lowest specific gravity, freezing point, proteolytic activity, lipase activity, RCT and HCT compared to cow and buffalo milk. Goat milk had highest refractive index compared to buffalo milk, whereas lowest refractive index compared to cow milk. Goat milk showed positive alcohol test at 75% (v/v) alcohol concentration. The curd formed from goat milk after 14 h was having very weak consistency. The goat milk has higher alkaline phosphatase activity, catalase activity compared to buffalo milk while it has lower alkaline phosphatase activity, catalase activity compared to cow milk.

Comparison of Surti goat milk with cow and buffalo milk for gross composition, nitrogen distribution, and selected minerals content.

AIM: The study was undertaken to find out the gross composition, nitrogen distribution, and selected mineral content in Surti goat milk, and its comparison was made between cow and buffalo milk. MATERIALS AND METHODS: Goat milk samples of Surti breed and buffalo milk samples were collected during the period from July to January 2014 at Reproductive Biology Research Unit, Anand Agricultural University (AAU), Anand. Cow milk samples of Kankrej breed were collected from Livestock Research Station, AAU, Anand. Samples were analyzed for gross composition such as total solids (TS), fat, solid not fat (SNF), protein, lactose, and ash. Samples were also analyzed for nitrogen distribution such as total nitrogen (TN), non-casein nitrogen (NCN), non-protein nitrogen (NPN), and selected minerals content such as calcium, magnesium, phosphorous, and chloride. Total five replications were carried out. RESULTS: Goat milk had the lowest TS, fat, protein, and lactose content among all three types of milk studied in the present investigation. On the other hand, the highest TS, fat, protein, and lactose content were found in buffalo milk. Buffalo milk had the highest SNF, calcium, magnesium, and phosphorous content, which was followed by goat milk and lowest in cow milk. The SNF, protein, TN, and calcium content of goat milk were statistically non-significant (p<0.05) with cow milk. The lactose content of goat milk was significantly lower (p>0.05) than that of the cow milk as well as buffalo milk. The goat milk had the highest ash and NCN content, which were followed by buffalo milk and lowest in cow milk. However, the differences in ash, NPN, and phosphorous content of three types of milk studied, viz., goat milk, cow milk, and buffalo milk were found statistically non-significant (p<0.05). The NCN content of buffalo milk was statistically non-significant (p<0.05) with cow milk as well as goat milk. The NCN and magnesium content of goat milk were significantly higher (p>0.05) than that of the cow milk. The magnesium content of goat milk was statistically non-significant (p<0.05) with buffalo milk. The chloride content of goat milk was significantly higher (p>0.05) than that of the buffalo milk as well as cow milk. CONCLUSION: It can be concluded from the study that the goat milk has lower TS, fat, lactose, protein content, TN as well as NPN but higher ash and NCN content compared to cow milk and buffalo milk. The goat milk has lower calcium, phosphorous compared to buffalo milk while it has higher calcium, phosphorous compared to cow milk, and it has higher magnesium, chloride content compared to cow milk and buffalo milk.

Blocked Lysine in Dairy Products: Formation, Occurrence, Analysis, and Nutritional Implications.

Lysine residues in milk proteins become "blocked" when they react with reducing sugars, particularly lactose, in the Maillard reaction. The blocked or glycated lysines reduce the biological availability of the lysine to metabolic processes and also hinder hydrolysis of the parent protein by digestive enzymes. Heating and storage of milk and milk products are the major promotants of the Maillard reaction and resulting chemical damage to the proteins. Several methods have been proposed to estimate the extent of this protein damage. Two major compounds, furosine, a product of acid hydrolysis of lactulosyl-lysine, the 1st stable product of the Maillard reaction, and carboxymethyl-lysine are used for assessing the early and advanced stages of the Maillard reaction, respectively. In addition, several methods are used for assessing the bioavailability of lysine in a protein; these include chemical, enzymic, and animal-based methods. This review discusses the Maillard reaction and its significance in milk and dairy products, methods of assessing the extent of the reaction and of the bioavailability of lysine, and the nutritional significance of blocked lysines and associated Maillard reaction products in milk proteins.

Comparison of five analytical methods for the determination of peroxide value in oxidized ghee.

In the present study, a comparison of five peroxide analytical methods was performed using oxidized ghee. The methods included the three iodometric titration viz. Bureau of Indian Standard (BIS), Association of Analytical Communities (AOAC) and American Oil Chemists' Society (AOCS), and two colorimetric methods, the ferrous xylenol orange (FOX) and ferric thiocyanate (International Dairy Federation, IDF) methods based on oxidation of iron. Six ghee samples were stored at 80 °C to accelerate deterioration and sampled periodically (every 48 h) for peroxides. Results were compared using the five methods for analysis as well as a flavor score (9 point hedonic scale). The correlation coefficients obtained using the different methods were in the order: FOX (-0.836) > IDF (-0.821) > AOCS (-0.798) > AOAC (-0.795) > BIS (-0.754). Thus, among the five methods used for determination of peroxide value of ghee during storage, the highest coefficient of correlation was obtained for the FOX method. The high correlations between the FOX and flavor data indicated that FOX was the most suitable method tested to determine peroxide value in oxidized ghee.