Combined effect of water activity and pH on the growth of food-related ascospore-forming molds

Abstract

Purpose The contamination of raw materials, packaging, or processing environments by fungal ascospores is a real concern for food industries, where variable rates of spoilage can be reached in pasteurized acidic products such as fruit juices, fruit jams, or soft drinks. The aim of this work was to assess the combined effect of aw and pH on the growth of six isolates from three genera of ascospore-forming molds that may occur in raw materials and in food industrial environments, in order to determine the environmental conditions that prevent the spoilage of pasteurized foods and beverages. Methods Growth tests were carried out on 60-day-old ascospores from Aspergillus hiratsukae (≡Neosartorya hiratsukae), Aspergillus thermomutatus (≡Neosartorya pseudofischeri), Chaetomium flavoviride, Chaetomium globosum, Talaromyces bacillisporus, and Talaromyces trachyspermus. The tests were performed up to 90 days at 25 °C, using sucrose solutions at different aw (0.85, 0.88, 0.92, 0.95) and pH (3.20, 3.50, 3.80, 4.20, 4.60) values. Growth was characterized by fitting an ordinary logistic regression model to the collected growth data. Results The explained percentage of the growth/no growth models ranged between 81.0 and 99.3%: aw exerted the largest influence on the growth of all tested species, while pH was significant only for Chaetomium isolates. The minimum conditions for germination and growth were aw 0.92 and pH 3.50 or 3.80, respectively, for C. flavoviride (46 days) and C. globosum (39 days), aw 0.92 and pH 3.20 for T. trachyspermus (13 days), aw 0.88 and pH 3.20 for T. bacillisporus (39 days), and aw 0.88 and pH 3.20 for the two aspergilli (33 and 27 days, respectively, for A. hiratsukae and A. thermomutatus). Conclusions Most of the spoiling mycetes tested were well-adapted to the formulations considered; therefore, foods strategies aiming to inhibit their growth should explore also the hurdle effect exerted by other factors (e.g., antioxidants, organic acids, oxygen levels).

Effect of Length of Storage and Chemical Additives on the Nutritive Value and Starch Degradability of Reconstituted Corn Grain Silage

“…In order to control fungal growth and spoilage in feed with a high concentration of DM, the application of propionic acid equivalents, in a concentration ranging from 12.5 to 30.0 g•kg −1 of water, was suggested. In addition, as the water concentration increases, more acid is needed to inhibit the development of molds [41]. In the present study, the rate of application, based on the manufacturer recommendations, was 2 L•t −1 (28%).…”

Exploring the Potential of Halotolerant Actinomycetes from Rann of Kutch, India: A Study on the Synthesis, Characterization, and Biomedical Applications of Silver Nanoparticles

“…Four different combinations ( Table 4 ) of pH and salt were used to study the haloalkaliphilic nature of the isolates. Control was kept without any stress [ 117 ].…”

The Role of Fungi in Food Production and Processing

“…Grains and cereals, rich in carbohydrates and moisture, provide favorable conditions for fungal proliferation, resulting in a diverse array of fungal inhabitants, including both beneficial and detrimental species [77]. In contrast, fruits and vegetables, with their acidic pH and antimicrobial compounds, exhibit a more limited fungal diversity, although certain spoilage fungi may still colonize these substrates under favorable conditions [78].…”