Effect of developed acidity and neutralization of milk on sensory, microstructural and textural changes in khoa prepared from cow and buffalo milk

Physico-chemical properties of Khoa prepared from lactose hydrolyzed buffalo milk

Lactose is a reducing sugar which is abundantly found in mammalian milk. Lactose intolerance affects more than 70% of the world population, being apparent by the absence of β-galactosidase enzyme, thus leading to the inability to consume dairy products. In the present work, Khoa was prepared from lactose hydrolysed milk and its physico-chemical, textural and microbiological quality were examined during storage at 5-7 °C for 28 days. The sensory quality of low lactose Khoa was comparable with that of the control Khoa up to the 14th day of storage. Significant differences (p < 0.05) between the acidity, hydroxyl methyl furfural (HMF) content, lightness, redness, springiness, chewiness and hardness values of the low lactose Khoa and the control Khoa were observed. The standard plate count (SPC), coliform and yeast and mould counts of the low lactose Khoa were within Food safety and standards authority of India (FSSAI) standards throughout the 28 days of storage. Therefore, the low lactose Khoa developed in this study had different physicochemical properties from the control sample with better shelf life.

Effect of quality of milk on physico-chemical characteristics of buffalo milk concentrate (khoa) during storage

The present work was conducted to evaluate the quality of milk (fresh/acidic/neutralized) on the physico-chemical, textural and fatty acid profile of khoa prepared from buffalo milk and stored in poly-alu-poly laminates for 30 °C/7 days and 5 °C/21 days, respectively. The degree of deterioration of common quality parameters was rapid during storage at 30 °C as compared to storage at 5 °C. Khoa stored at 30 °C showed greater variation in various physico-chemical and textural parameters as compared to khoa stored at 5 °C. Acidity, ash, tyrosine value, furosine, HMF, FFA, peroxide value, TBA value, butyric acid and stearic acid showed an increasing trend whereas, decrease in pH and oleic acid was observed as storage period progressed. Noticeable changes were observed in textural attributes of khoa during storage. However, the SDS-PAGE pattern of caseins from different types of khoa showed almost negligible deviation during storage.

Effect of type and quality of milk on heat induced protein-protein interactions in khoa

The present study was carried out to evaluate the effect of developed acidity and subsequent neutralization of milk (cow/buffalo) on heat induced protein-protein interactions occurring at various stages during khoa preparation. Protein-protein interactions were studied in terms of surface hydrophobicity (Fmax), sulfhydryl (-SH) group and SDS PAGE. As milk progressed to boiling stage, increase in Fmax and decrease in -SH content was observed. Khoa prepared from cow milk had comparatively higher values for Fmax and lower values for -SH group. Fmax was observed to be highest in acidic samples followed by neutralized and fresh samples. While considering -SH group, maximum values were observed in neutralized samples followed by acidic and fresh samples of both milk and khoa. However, no visible difference was observed in SDS PAGE patterns of casein fractions isolated from different types of samples. The bands of β-lg and α-la did not resolve clearly in the khoa samples due to high heat treatment involved in its preparation, indicating intense denaturation of whey proteins especially in neutralized samples where an alkaline medium resulted in strong binding between casein and whey proteins. The quality of milk also resulted in altered heat induced protein-protein interactions in khoa.

Determination of forced convection heat transfer coefficients and development of empirical correlations for milk in vessel with mechanical agitators

Heating of milk is an important unit operation to produce many milk based products. This process is done either in heat exchangers or in agitated vessels, where the mode and type of heat transfer plays a significant role. Use of mechanical agitator with suitable impeller would result in uniform agitation of the liquid. Data for forced convection heat transfer coefficients for milk in agitated vessel have not been documented. In the present investigation, forced convection heat transfer coefficients for milk, using mechanical agitators in vessels have been determined. Experiments have been conducted in vessels (Baffled as well as Unbaffled vessel) that were designed and fabricated under standard procedure employing: (1) Flat Six Blade Turbine impeller, (2) Inclined Six Blade Turbine impeller, (3) Three Blade Propeller impeller and (4) Two Bladed Paddle. Heat transfer coefficients were determined for h¯ for cow milk (3.5% fat), standardised milk (4.5% fat) and full cream milk (6.0% fat). The Two Bladed Paddle was found to as yield the highest heat transfer coefficient h¯ for all three types of milk. In addition, empirical correlations for the forced convection heat transfer using Nu=a·Reb·Pr0.33 have been developed for each case. These heat transfer correlations derived will find application in large scale design and the experimental setup would be useful for future investigation with different liquids and impellers.

Effect of quality of milk on maillard reaction and protein oxidation during preparation of cow and buffalo milk khoa

The browning indicators (Lactulose, HMF and Furosine) and protein bound carbonyls were used to assess the effect of developed acidity and subsequent neutralization of milk at various stages of khoa (heat desiccated milk product) preparation. Available lysine was also analyzed in raw milk and final product i.e. khoa. Available lysine decreased as milk progressed to khoa preparation. Present study indicated that increase in heating intensity resulted in increased concentration of browning indicators and protein bound carbonyls (PC) in boiled milk and khoa. Concentration of browning indicators was found to be significantly higher in buffalo milk and khoa samples whereas, PCconc. was higher in cow milk and khoa samples. Neutralization of milk significantly affected Maillard reaction by elevating concentration of browning indicators and PC in both milk and khoa.