RESUMO
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.
RESUMO
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 ß-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.
RESUMO
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.
RESUMO
Khoa is a heat desiccated milk product which serves as base material for traditional dairy based Indian sweets. Sensory, textural and microstructural changes in khoa were studied to assess the effect of developed acidity and neutralization of milk. Noticeable changes were observed in sensory, textural and micro structural quality of khoa as affected by quality of milk. Lower hardness, springiness, cohesiveness and accordingly, gumminess and chewiness were observed in khoa manufactured using neutralized milk due to higher moisture retention as compared to control and acidic milk khoa. It was also evident from the Scanning Electron Microscopy that higher moisture retention in neutralized milk khoa resulted in elongation of native microstructure of khoa by suppressing the grain formation leading to smooth and plain surface while, developed acidity in milk resulted in greater granule formation in the resulting khoa causing shrinkage of native microstructure and acidic flavour in khoa. Similarly, acidification and subsequent neutralization of milk adversely affected sensory attributes of resulting khoa.