Aktivnost zgrušavanja mlijeka i primarna proteoliza liofiliziranog ekstrakta cvijeta artičoke (Cynara scolymus L.)

Research background. A few studies have investigated Cynara scolymus enzymes as a substitute for calf rennet in cheese making. They used aqueous extracts prepared by maceration of plant material and stored by freezing. However, it was indicated that lyophilisation is a better alternative to preserve the coagulant properties of plant extracts over a longer period of time, as it is a more controllable, stable and hygienic alternative with a better shelf life that is easier to transport, store and standardise. Experimental approach. We obtained a lyophilised extract of mature artichoke flowers, named CS, which was characterised for its milk-clotting properties at different pH and temperatures. In addition, the potential yield, whey composition and the primary hydrolysis profile of caseins by urea-polyacrylamide gel electrophoresis (PAGE) of mini curds prepared with different doses of coagulant were determined. Results and conclusions. The lyophilised extract was able to hydrolyse casein and showed stable proteolytic activity at pH=6.4 and 37 °C for 50 min, which decreased when the process temperature was increased to 41 and 45 °C and was lost at 70 °C. On the other hand, milk-clotting activity increased significantly (p<0.001) when the temperature increased from 37 to 45 °C and the pH of the milk decreased from 6.8 to 5.8. Potential yield ​​between 10 and 17 % was obtained for the mini curds prepared with the lyophilised artichoke extract, and the casein degradation pattern obtained by urea-PAGE was similar to that of the commercial coagulant. Novelty and scientific contribution. On a laboratory scale, our work has shown that the lyophilised artichoke extract has sufficient proteolytic and coagulant activity to be used as a milk coagulant, i.e. plant rennet, in cheese making as an alternative to animal rennet. As this extract is lyophilised, it has the advantage of being a better alternative in terms of preservation and shelf-life. It offers an innovative way to diversify cheese products and appeal to consumers with different dietary preferences and needs.Pozadina istraživanja. U nekoliko je istraživanja ispitana primjena enzima dobivenih iz artičoke (Cynara scolymus) kao zamjena za teleće sirilo u proizvodnji sira. U njima su korišteni vodeni ekstrakti dobiveni maceracijom biljnog materijala te skladišteni zamrzavanjem. Međutim, pokazalo se da se liofilizacijom bolje očuvaju koagulacijska svojstva biljnih ekstrakata tijekom duljeg skladištenja, jer ih je jednostavnije kontrolirati, održati stabilnima i higijenski ispravnima, a mogu se i dulje vrijeme skladištiti te lakše distribuirati i standardizirati. Eksperimentalni pristup. U ovom smo radu pripravili liofilizirani ekstrakt cvijeta zrele artičoke, te opisali njegova svojstva zgrušavanja mlijeka pri različitim pH-vrijednostima i temperaturama. Osim toga, određeni su mogući prinos, sastav sirutke i uzorak razgradnje kazeina u grušu pripremljenom u malim porcijama s različitim količinama sredstva za koagulaciju, ispitanom elektroforezom na poliakrilamidnom gelu s dodatkom uree. Rezultati i zaključci. Liofilizirani ekstrakt je razgradio kazein i imao stabilnu proteolitičku aktivnost pri pH-vrijednosti od 6,4 i temperaturi od 37 °C tijekom 50 min, koja se smanjila pri porastu temperature na 41 i 45 °C, a potpuno nestala pri 70 °C. Nasuprot tome, aktivnost zgrušavanja mlijeka se bitno povećala (p