Factors affecting the thermal activation of Neosartorya fischeri in pineapple and papaya nectars

Abstract

In this research factors that influence the activation of Neosartorya fischeri ascospores (heating medium, temperature of production and age of the ascospores) were studied. The heating medium used was pineapple and papaya nectars at different ratios (ºBrix/acidity). Lower activation times were observed for the N. fischeri ascospores in pineapple and papaya nectars under the conditions of temperature and production age of 25ºC for 1 month and using ratios of the heating medium of 10 for pineapple nectar and 26 for papaya nectar. In these cases, the activation time was 5 minutes for the pineapple nectar and 10 minutes for the papaya nectar at 85ºC. For the ascospores produced at 35ºC over three months, heated in pineapple nectar at a ratio of 38 and in papaya nectar at a ratio of 66, the longest activation times of 15 and 20 minutes, respectively, were observed. The statistical analysis showed that the factors which had the most influence in the activation time of the ascospores were the ratio and the production temperature of ascospores.

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

“…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. Activation of spores has also been reported with thermal processed (105e120 C, 5e30 min) bacterial spores such as Bacillus stearothermophilus spores (Corradini, Normand, Eisenberg, & Peleg, 2010;Finley & Fields, 1962).…”

“…However, it has been recognized that the thermal process may activate the dormant ascospores of moulds which subsequently cause deterioration, hence resulting in economic loss (Katan, 1985;Slongo & Aragão, 2006;Splittstoesser, Nielsen, & Churey, 1993). Increasing the intensity (temperature or processing time) of the heat treatment is not desirable, due to quality reasons and consumer demands for 'fresh-like' fruits.…”

Modeling the influence of water activity and ascospore age on the growth of Neosartorya fischeri in pineapple juice

“…The effects of this factor on the heat inactivation of mold spores have been reported in the literature. Slongo and Aragão (2006) found that ascospore age influences the heat resistance of N. fischeri in papaya and pineapple juices. However, little information is available related to the effect of this factor on the growth of molds.…”

Growth of Byssochlamys nivea in pineapple juice under the effect of water activity and ascospore age

“…Some more heat resistant species owe their heat resistance to thick walled sexual ascospores, which can survive to thermal processes usually applied in the food production, including the production of fruit juices (23). Ascospores can be activated by the process’ temperature, being able to germinate and grow into the package during storage, reducing the product’s shelf life and causing economic losses (17). Extremely resistant species such as Byssochlamys nivea , Byssochlamys fulva , Talaromyces flavus and Neosartorya fischeri serve as standards for spore resistance and their absence indicates the quality of sterilization processes (7).…”