Studies on acceleration of Ras cheese ripening by aminopeptidases enzyme from buffaloes' pancreas. I. purification and characterization of buffaloes pancreas aminopeptidas

Aminopeptidaes [EC. 3.4.11.1] was purified from fresh buffaloes pancreas by ammonium sulfate fractionation at 30-40% saturation [w/v], followed by gel filtration chromatography on sephadex G-l 00 column about 9.6 fold with 20% recovery of crude extract. The enzyme had a molecular weight [MW] about 20 kDa by gel filtration chromatography on sephadex G 100 column. The purified enzyme exhibited maximum activity on leucine-p-nitroanilide pH 6.0 and 40°C. The enzyme was strongly activated by 1 mM of Ca [+2], Na[+], respectively, but strongly inhibited by 1 mM of Cu[+]2 and Cd[+]2. The purified aminopeptidase activity was not significantly affected by I mM of EDTA and 1, 10 Phenanthroline

Utilization of purified and characterized lipase from papaya [Carica papaya] in acceleration of ras cheese slurry

The lipase enzyme from papaya [Carica papaya] was purified by ammonium sulphate solution [40-50%] and fractionated by gel filtration on sephadex G-100. Throughout the overall process, the final purification was 9.32, 13.16, 6.94 and 10.32 folds of F1, F2, F3 and F4 respectively. The optimum pH for all previous fractions was at 7.0. Crud extracted lipase was used to accelerate cheese slurry ripening with concentrations of 2.0 and 4.0 ml/100 g curd. Slurries were incubated at 37° for 7 days. All slurries were analyzed for acidity, pH, moisture, SN/TN, T.V.F.A. and flavour evaluation. The results indicated that the ripening indices of all slurries [pH, acidity, SN/TN and T.V.F.A.] gradually increased as ripening period progressed. Also, flavour of all slurries gradually improved during incubation period [7 days, 37°]. Progress of flavour score with slurry [2ml lipase/100 g curd] after 3 days was close to control after 7 days; while with slurry [4 ml lipase/100g curd] after one day close to control after 7 days. At the end of incubation period slurry with 4 ml/100g curd had a high total volatile fatty acids content and the same time had a high flavour scoring

Studies on ras cheese ripening with enzymes addition. 1. Preparation of lipase and protease from bacteria and its addition to ras cheese slurry

Ten microbiolgical sources were screened for abilites to produce proteolytic and lipolytic activities. Three organisms were selected from them for proteolytic activity and lipolytic activity. Both of them were used to accelerate cheese slurries ripening with concentrations of 0.5, 1.0 and 1.5 ml / 100 g curd. Slurries were incubated at 37° for 7 days. The best results were obtained when Lactobacillus delbrueckii subsp. bulgaricus was used for both protease and lipase

Studies on ras cheese ripening with enzymes addition. 2. Application of bacterial proteases and lipases in accelerating ripening of ras cheese

The preliminary experiments on slurry [1] were used to accelerate Ras cheese ripening. Mixture of protease and lipase: being 1.0 ml and 1.5 ml / kg were used. Cheese moulds were ripened at 12° for 4 months. Cheese samples were weekly analysed for ripening indices, chemical analysis and organoleptic properties. After 3 months cheese resultant was exposed for U.V. rays for 2 min to stop the lipase activity and keep the cheese without deterioration. From the results, it could be concluded that the use of mixture enzyme shortened the ripening period of Ras cheese and saved about 50% of ripening period. Also hasted the flavor development and improved the characteristics of body and texture

Production and characterization of bacterial coagulants as calf rennet replacer for Egyptian cheese making.

The bacterial coagulant as calf rennet replacer was aimed to evaluate. The productivity and milk clotting activity [MCA] of coagulants of 12 strains of B. subtilis and 9 strains of B. megaterium were screened. Specific activities of coagulants were tested whether in the crude or in the purified form. The chemical, physical, microbial and organoleptic properties of Ras cheese slurry, coagulum and Domiati cheese [from conventionally salted milk] made with bacterial rennet [concentrated by dialysis against polyethelenglycol 40%] were investigated. Five strains of B.subtilis and three strains of B.megaterium produced milk clotting enzyme [MCE] with MCA> 100 SU/mI, after incubation for 7 days at 30°. The max. relative MCA was recorded at milk temperature of 65° for both types of bacterial rennet in the crude form and increased to 75° [B.subtilis] or 80° [B.megaterium] when purified. While the purification did not change the sensitivity of bacterial coagulants to NaCI or CaC1[2] concentration, where the former salt inhibited while the latter one improved the MCA. The purified enzyme of B.megaterium exhibited higher km and lower Vmax than those occurred by that of B.subtilis.Ras cheese slurry made with B.subtilis rennet matured after 5 days of incubation at 37° and was slightly higher in the flavour score than that of B.megaterium. Both slurries of bacterial rennet possessed a stimulating effect on the growth of the starter cultures added. Bacterial rennet coagulum was softer and synersed lower whey amount than that of calf rennet. Bacterial rennet had also an accelerating effect on Domiati cheese ripening as appeared from the ripening indices determined. Some weakness in the consistenôy associated with Domiati cheese made with bacterial rennet but the flavour score was better after one month and then slightly lowered after two months than the control pickled for the same period