Note: Influence of different heating media on thermal resistance of Neosartorya fischeri isolated from papaya fruit

Abstract

E. RAJASHEKHARA, E.R. SURESH AND s. ETHIRAJ. 1996. A heat-resistant mold identified as a strain of Neosartorya jischeri was isolated from microbiologically spoiled papaya fruits. The optimum heat activation temperature and time for the ascospores of the test mold was found to be 80°C for 15-30 min. The decimal reduction times (D-values) at 85", 87" and 89°C in phosphate buffer (pH 7.0) as heating medium were 35.25, 11.1 and 3.90 min respectively and hence the calculated z-value was 4.0"C. In grape and mango juices as heating media, the D,,oc and the DsjOc values were increased as the "Brix level raised from 10 to 45. In commercial fruit juices of mango, orange, pineapple and mango-pineapple blend as heating media DRsOc values were greater than those observed for phosphate buffer.

Modeling the inactivation of Neosartorya fischeri ascospores in apple juice by high pressure, power ultrasound and thermal processing

“…Beuchat (1986) also observed N. fischeri FRR 1833, FRR 2334, and FRR 110483 ascospore activation up to 4.5 logs in buffer by 75 and 80 C thermal processes during the first 15e45 min. Other investigators reported lower spore activation (0.25e0.8 log) between 10 and 50 min with N. fischeri (E7, C3, and isolated from spoiled papaya fruit) spores in buffer at the same temperatures which is similar to our results (Amaeze & Ugwuanyi, 2011;Rajashekhara, Suresh, & Ethiraj, 1996). Slongo and Aragão (2006) found that temperature of 85 C between 10 and 20 min was required for maximum activation of N. fischeri ascospores in pineapple and papaya nectar, however the level of activated spores was not mentioned.…”

“…The Weibull model has been used by Sant'Ana et al (2010) for the thermal inactivation of Byssochlamys fulva ascospores in apple juice. The majority of previous thermal studies found nonlinearities for N. fischeri log survivors (Beuchat, 1986;Kotzekidou, 1997;Rajashekhara et al, 1996;Salomão, Slongo, & Aragão, 2007), but used first order or linearized first order model proposed by Alderton & Snell (1970) to estimate the kinetic parameters. Although the error is higher and fitting not so good (0.924 R 2 , 0.365 MSE, 1.27 A f ), the first order D 90 C of 4.9 min was also determined to be able to compare with past results.…”

Heat resistance of Neosartorya fischeri in various juices

“…Spoilage by heat-resistant fungi is a major problem for fruit-processing industries and has been documented in many countries (Baglioni, Gumerato, & Massaguer, 1999;Kotzekidou, 1997;Obeta & Ugwuanyi, 1995;Rajashekhara, Suresh, & Ethiraj, 1996;Suresh, Ethiraj, & Jayaram, 1996). Contamination of processed fruits by fungi originates in fields and orchards, where the fungi have been isolated (Tournas, 1994).…”

Heat resistance and the effects of continuous pasteurization on the inactivation ofByssochlamys fulvaascospores in clarified apple juice

“…Nevertheless, the occurrence of deterioration episodes (Olliver and Rendle 1934;Obeta and Ugwuanyi 1995;Rajashekhara et al 1996;Suresh et al 1996;Kotzekidou 1997;Baglioni et al 1999) indicates that the stage to which microbiological stability and safety of the fruit juices (pasteurization) is attributed, may not, on its own, be efficient in reducing ⁄ eliminating even low loads of these contaminants. This can be due to the elevated heat resistance of mould ascospores (Tournas 1994) or to log-linear kinetics behaviour followed by some micro-organisms.…”