Effect of heat treatment of milk on the physicochemical, microbiological and sensory characteristics of white cheese (Gibna bayda)

This study was conducted to determine the effect of heat treatment of milk on the physicochemical, microbiological, and sensory characteristics of white cheese (Gibna bayda).  The cheese was made from raw warmed (45 °C) milk (T1) and heat-treated (72 °C/1 min) milk (T2) to which the starter culture (2% w/w), sodium chloride (2% w/w) and CaCl2 (0.02% w/w) were added. After manufacture, cheese was preserved at 5 °C for 45 days and subjected to physicochemical, microbiological, and sensory analysis.  The results revealed that T2 had longer coagulation time (75.5 min) and higher cheese yield (17.1 kg/100 L) compared to T1.  Fat (25.28%), moisture (55.70%), and ash (6.40%) contents were higher in T1, while protein (18.51%), total solids (47.49%) contents, and acidity (0.56%) were high in T2.  Total viable bacteria [TVB] (log10 6.64 cfu/gm), Staphylococcus aureus (log10 1.88 cfu/gm) and yeasts and moulds (log10 5.53 cfu/gm) counts were high in T1, while Escherichia coli count was log10 <1.0 cfu/gm in both treatments.  T1 scored better in taste (2.43), body (2.26), and overall acceptability (2.79), while T2 scored better in colour (3.44), flavour (2.79), and T2 cheese was slightly salty (1.45) than T1 cheese. The study concluded that heat treatment of milk improved some physicochemical and sensory characteristics of cheese, and heat-treated milk cheese was safer for human consumption than raw milk cheese.