ELSEVIER zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Food Research International, Vol. 28, No. 6, pp. 531- 535, 1996 Copyright 0 1996 Canadian Institute of Food Science and Technology Published by Ekvier Science Ltd Printed in Great Britain 0963-9969196 $15.00 + 0.00 0963-9969(95)00004-6 On water dynamics and germination time of mold spores in concentrated sugar and polyol solutions zyxwvutsrqpo Jorge Chirife,” H&&or H. L. Gonzailezbpc & Silvia L. Resnikd ‘Departamento de Industrias, Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires, (1428) Buenos Aires, Argentina ‘Member of CONICET, Argentina ‘Facultad de Ingenieria, Universidad de Buenos Aires dA4ember of Comision de Investigaciones Cient@ cas de la Provincia de Buenos Aires The relative effect of concentrated solutions of selected glass formers on germi- nation time at 28°C of mold spores of Aspergillusflavus, A. niger and Eurotium herbariorum was determined. Solutes included glucose, fructose, mannose, glyc- erol, sucrose, maltose and propylene glycol. The effect of fructose concentration on the germination time of A. parasiticus was also studied. The results did not agree with previous literature experimental data used to support a ‘water dynamics’ approach of microbial stabilization in concentrated sugar and polyol solutions. Copyright 0 1996 Canadian Institute of Food Science and Technology. Published by Elsevier Science Ltd. Keywords: glass transition, water activity, water dynamics, germination, molds. INTRODUCTION Germination of a mold spore is a physiological reac- tion of a resting cell to changes in environmental con- ditions; germination can conveniently be divided into two stages: a period of increase in spore size (swelling phase), followed by the protrusion of the germ tube (Garraway & Evans, 1984). The morphological events of germination, swelling, and germ tube emergence are accompanied by changes in respiration and macro- molecular synthesis (Griffin, 1981). In general, fungal spores will not germinate under conditions of unfavor- able temperature, moisture, oxygen, or pH, although the absolute requirements vary considerably among species. Water is a predominant part of germination, and hydration of the medium is an important para- meter (Gervais et al., 1988). Slade and Levine (1986) compared the inhibitory effects for a series of concentrated solutions of selected glass-farmers, including glucose, fructose, mannose, maltose, sucrose, glycerol, on the germination of Asper- gillus parasiticus conidia. They also reported the germi- nation time of A. parasiticus in concentrated fructose solutions in the range 4&70% (w/w). The various glass formers were assayed in pairs, deliberately matched as to the individual parameters of approximately equal relative vapour pressure (RVP). Slade and Levine (1986) concluded that the observed rates of germina- tion of A. parasiticus spores in the different sugar and polyol solutions can be analyzed as a mechanical relax- ation process which is governed by the translational mobility of water. They added that the results obtained demonstrated the failure of the water activity (a,) con- cept to predict relative efficacy of solutes for antimicro- bial stabilization, and also proved that ‘water dynamics’ may be used (instead of water activity) to predict the microbial stability of concentrated and intermediate moisture systems. In subsequent papers they made ref- erence to their experiments on A. parasiticus as a demonstration of the usefulness of ‘water dynamics’ to predict microbial stabilization of concentrated food systems (Slade & Levine, 1987, 1991). It is the purpose of the present work to test the ‘water dynamics’ approach of Slade and Levine (1986) to interpret the effect of different sugar/polyol solutions on the germination time of various mold spores. 531