Caseinolytic activity of fruit extract from Opuntia ficus-indica on bovine, caprine, and ovine sodium caseinates

Isolation and Partial Characterisation of Milk-clotting Aspartic Protease from Streblus asper

A rennin-like milk-clotting protease from the twigs of Streblus asper was purified by a factor of 65 times with 36% recovery using ethanol precipitation, ion-exchange and size-exclusion chromatographic techniques. The enzyme was found to be monomeric in nature having a molecular mass of 55kDa. The enzyme acts optimally at 55°C and was stable in the temperature range of 30–40°C. Easy enzyme inactivation by moderate heating, makes this protease extract potentially useful for cheese production. The purified enzyme is an acid protease with an optimum pH of 5.5 and it retained 96% of its residual activity between pH 5.0 and 6.0. Pepstatin A inhibited the proteinase activity, whereas iodoacetamide, phenylmethyl sulphonyl fluoride, β-mercaptoethanol and ethylenediaminetetraacetic acid had no significant inhibitory effect suggesting the presence of aspartic acid residue at the active site. The milkclotting aspartic protease showed predominant α-helical conformation in phosphate buffer as evidenced from circular dichroic spectroscopy.

Digestive enzymes of the crustaceans Munida and their application in cheese manufacturing: a review

Crustaceans Munida (fam. Galatheideae, ord. Decapodi) were fished in the Southern Adriatic Sea and their proteolytic activities were characterized and tested for potential application in cheese manufacturing. Enzymes extracted from whole crustaceans, mainly serine proteases, showed high caseinolytic and moderate clotting activities. Analysis by 2D zymography of the digestive enzymes extracted from Munida hepatopancreas, showed the presence of several isotrypsin- and isochymotrypsin-like enzymes in the range of 20–34 kDa and 4.1–5.8 pI. Moreover, specific enzymatic assays showed the presence of aminopeptidases and carboxypeptidases A and B. Overall, optimum activity was achieved at pH 7.5 and 40–45 °C. Caseinolytic activity, determined both spectrophotometrically and by SDS gel electrophoresis, indicated higher activity on β-casein than on α-casein. Miniature cheddar-type cheeses and Pecorino-type cheeses were manufactured by adding starter, rennet and Munida extracts to milk. Reverse-phase HPLC and MALDI-ToF mass spectrometry showed a more complex pattern of proteolytic products in cheeses made using Munida instead of chymosin. Munida extracts were found to degrade the chymosin-derived β-casein fragment f193–209, one of the peptides associated with bitterness in cheese. In conclusion, Munida digestive enzymes represent a promising tool for development of new cheese products and shorten cheese ripening when used either alone or in addition to calf rennet.

Proteolysis in miniature cheddar-type cheeses manufactured using extracts from the crustacean Munida as coagulant

Miniature (20 g) Cheddar-type cheeses were manufactured using enzymes extracted from the crustacean Munida or chymosin as coagulant. Cheeses were ripened at 8 degrees C and samples were collected for analysis after 2, 6 and 12 weeks. Proteolysis was assessed by urea-polyacrylamide gel electrophoresis, which showed that cheeses manufactured with the Munida extracts had a higher extent of degradation of beta-casein than cheeses made using chymosin as coagulant. Patterns of proteolysis were also obtained by reverse-phase high-performance liquid chromatography (RP-HPLC) and matrix assisted laser desorption ionisation-time of flight (MALDI-ToF) mass spectrometry. In general, the products of proteolysis were more complex in cheese made using the Munida extracts than in cheese made by chymosin as coagulant. Statistical analysis of results clearly discriminated the cheeses on the basis of coagulant used. Molecular mass of peptides found in cheese made using Munida extracts were similar to those of peptides commonly detected in cheeses made using chymosin as coagulant.

Cactus stems (Opuntia spp.): A review on their chemistry, technology, and uses

Although traditionally used as a valuable health supporting nutrient, the vegetative parts of Opuntia spp. plants are scarcely used in modern nutrition and medicine. While all kinds of different Opuntia spp. have been studied, a systematic approach regarding the inter-relationships between the composition and the pre- and postharvest conditions is still missing. Therefore, the present review compiles and discusses literature on the chemical composition of cactus stems, the knowledge on uses in food, medicine, and cosmetics. It is concluded that much research is needed to get an insight into the multitude of bioactivities reported in the traditional literature but also to take advantage of the respective constituents for food and pharmaceutical applications.