The influence of ultrafiltration on sheep milk rennet clotting properties
Advancing the chemical engineering fundamentals
Filtration (T2-11P)
Keywords: Ultrafiltration, sheep milk, renneting properties
In the cheese-making process, ultrafiltration (UF) of the milk could be used to concentrate the milk proteins. Rennet clotting properties (RCP) are extremely dependent on the milk concentration and therefore it is critical a systematic study of the ultrafiltration at different concentration factors. Several studies have been done with cow’s milk, but given the differences in milk composition the results shouldn’t be extrapolated for sheep milk.
This work addresses the investigation of sheep milk ultrafiltration (UF) at different operating conditions and its effect on the rennet clotting properties (RCP), namely rennet clotting time (RCT), rate of curd firming (k20) and curd firmness. UF experiments were carried out in concentration mode by varying the concentration factors from 1.2 to 2.0 that represented protein contents ranging from 4.8% to 10.6%. The UF unit (Celfa) with 25.5 x 10–4 cm2 of membrane surface area was equipped with a cellulose acetate membrane with molecular weight cut-off (MWCO) of 7000 Da.
The evolution pattern of the RCP of skimmed sheep milks feeds and retentates were assessed by Optigraph. A significant increase on curd firmness was detected with increasing protein concentration, whereas a decrease on the curd firming rate was observed. The behavior of curd firmness and curd firming rate with the protein concentration was linear and correlations were established.
Skimmed milk concentrated by ultrafiltration leads to higher cheese making yields and to the improvement of RCP evaluated by the firmness parameters.
Presented Tuesday 18, 13:30 to 15:00, in session Filtration (T2-11P).
