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Journal of Food and Nutrition Research
Online First Articles

Pohůnek, V. – Adamcová, M. – Kulišanová, I. – Šístková, I. – Rohlík, B.-A. – Ševčík, R.
Thermal inactivation of Aspergillus lacinosus ascospores as a function of temperature and soluble solids content in fruit jam

Václav Pohůnek, Department of Food Preservation, Faculty of Food and Biochemical Technology, University of Chemistry and Technology Prague, Technická 5, 16628 Prague 6 – Dejvice, Czech Republic. E-mail: vaclav.pohunek@vscht.cz

Received 27 March 2019; 1st revised 16 May 2019; 2nd revised 7 June 2019; accepted 11 June 2019; published online 10 September 2019

Súhrn: Moulds are the most frequently occurring spoilage microflora in jams, in particular the heat-resistant species of the Byssochlamys, Neosartorya and Aspergillus genera. An alarming number of uncommon heat-resistant isolates, such as Aspergillus lacinosus, with unknown thermal inactivation kinetic parameters, decimal reduction times (D values), were detected in recent studies. Aspergillus lacinosus, an ascospore-forming mould was isolated from commercially produced jams with reduced sugar content, during a thermal death study. The aim of our study was to determine D values for A. lacinosus in three types of matrices: physiological solution (PS, pH 6.6, refraction Rf = 1.2 °Brix), low-sugar jam (LSJ, pH 3.5, Rf = 57 °Brix) and extra-sugar jam (ESJ, pH 3.5, Rf = 65 °Brix) at 70–95 °C. ESJ was premium quality jam with minimal content of fruits 450 g per kilogram of product. Data obtained from thermal death curves showed various D values of A. lacinosus in these matrices, i.e. (23.25?±?7.21) min for PS, (8.18?±?3.56) min for LSJ and (4.89?±?1.89) min at 85 °C for ESJ. It was observed that ESJ had the lowest D value from all matrices for each temperature. Calculation of the temperature sensitivity of microorganisms (z values) showed the same phenomenon, the values ranging from 17.2 °C to 38.7 °C for strawberry jams and from 20.3 °C to 21.8 °C for forest fruit jams.

Kľúčové slová: heat-resistant mould; thermal treatment; inactivation; decimal reduction time; thermal sensitivity; thermal death curves

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