Abstract:
The current study was conducted at Haramaya University Dairy laboratory with the main
objective of investigating how heat treatment affects whey proteins and rennetability
property of camel milk for cheese making. Completely randomized design (CRD)was used
by evaluating effect temperature (heated at 400C,650C/30min,720C/30 sec, 750C/5 min,
850C/5 min and 900C/5 min).Unheated milk used for alternative reference during chemical
and whey protein denaturation evaluation. Similar experimental setup was also used for
cow milk for reference. Heat treatment was done in thermostatically controlled water bath.
The chemical composition of milk analysed using milkoscan, whey protein denaturation
analysis was done using gel electrophoresis and kjeldahal method. While for rennetabilty
properties parameters Rheometery ReoRox G2-4 was used. The result showed that raw
camel milk significantly (P<0.05) had lower percentage of protein, solid non-fat, casein
and lactic acid than cow milk. Heat treatment have no significant effect (P>0.05) on gross
chemical content of camel and cow milk. Total whey protein denaturation % increased
(P<0.05) as heating temperature increased in both camel and cow milk. In camel milk α-
lactalbumin (α-La)showed less denaturation while Camel serum albumin denatured at
higher heat treatment as band become invisible. While in cow milk β-lactoglobulin and α-
La denatured as temperature level increased while bovine serum albumin the denaturation
percentage increased constantly as temperature increased. Gelation time, and Time to
G'max were significantly increased(P<0.05) as heat treatment increased while G'max was
lowered as heating temperature increased for camel and cow milk. For camel milk short
(6min) gelation time was observed for heated at 400C while it increased to 14 min at 650C.
Significantly lower G'max observed at 75,85 and 900C/5min for camel while for cow milk
at 900C/5min. From heat treated higher at 650C/30min (51pas for camel and 111 for cow)
than the other temperatures. Similarly, time to G'max was also increased as heat treatment
increased. Pre heat treatment of milk can determine the gelation time and curd
aggregation property of cheese. Therefore, lower Pasteurization temperature that results
less denaturation of whey protein was optimal for cheese milk treatment. Pasteurization
temperature at 720C/30 sec can also be an alternative for cheese milk treatment to utilize
whey proteins without affecting coagulation processes.
