Effect of gelation temperature on the properties of skim milk gels made from plant coagulants and chymosin

Reconstituted skim milk was gelled at 25–40C with the plant-origin coagulants fromCynara cardunculusL. orCynara humilisL.or with fermentation-produced chymosin. Gel formation and ageing were monitored by low amplitude oscillatory rheology andconfocal scanning laser microscopy. Arrhenius plots for the rate of mil kgelation were also determined. Plant coagulants had shortergelation time (tg)at25C, 35C and 40C, and higher initial rate of increase inG0values at all temperatures tested. The firmest gelsat long ageing times were produced by chymosin at 30C and 32C. At a gelation temperature of 25C, the differences in rheologicaland microstructural characteristics between plant coagulants and chymosin were considerable; plant coagulants had shortertgandhigherG0values. For the lowest gelation temperatures, plant coagulants had smaller activation energy values for gelation. Most ofthe gelation results were similar between plant coagulants, but some differences were found in the values oftg;the rate of increase inG0and loss tangent parameter. The characteristics of gels produced with plant coagulants were influenced less by the changesin temperature compared with chymosin-produced gels, which may be an important consideration in using plant-origin coagulantsin the production of cheeses with a wider range of gelation temperatures