Abstract
Abstract Spore forming bacteria can play an important role in food quality and safety as spoilage and pathogenic microorganisms due to resistance to heat-treatment. However, there are limited number of studies focused on evaluate the microbiological quality and the occurrence of these bacteria in UHT goat milk, soymilk and dairy beverage of goat milk and soy protein. In this context, 75 samples of these beverages were evaluated regarding heterotrophic mesophilic microorganisms by conventional plate count and selective methods to detect microorganisms from Bacillus cereus group and Clostridium perfringens. Population counts greater than 104 CFU.ml-1 of heterotrophic mesophilic microorganisms were observed in 80% of the lots of goat milk and 100% of the lots of soymilk and dairy beverage of goat milk and soy protein. The presence of bacteria belonging to B. cereus group was observed in 16%, 52% and 44% of goat milk, soymilk and dairy beverage of goat milk and soy protein, respectively. C. perfringens was isolated from 8% samples of UHT soymilk. The frequency of genes hblA, hblB, hblC, nheA, nheB, nheC in 29 isolates obtained from these products was 62%, 48.2%, 96.5%, 79.3%, 68.9% and 79.3%, respectively. The microbiological quality of the evaluated products was unsatisfactory.
Highlights
Spore forming microorganisms can be present in dairy products, and they are usually associated with spoilage of milk and dairy products, especially those processed under high temperature, including powder milk, canned dairy products, goat milk, cow milk and some cheeses (Eijlander et al, 2019; Jindal & Anand, 2018; Pinto et al, 2018; Oliveira et al, 2016c; Vidal et al, 2016; Reindl et al, 2014)
This study focused on count populations of heterotrophic mesophilic microorganisms, the bacteria belonging to Bacillus cereus group and C. perfringens in Ultra Hight Temperature (UHT) treated goat milk, soymilk and dairy beverage based on combination of goat milk and soy proteins, and posteriorly verify the diarrheagenic potential of the isolates belonging to B. cereus group
The presence of bacteria belonging to B. cereus group, that comprises Bacillus anthracis, Bacillus mycoides, Bacillus thuringiensis, Bacillus cereus, Bacillus pseudomycoides, Bacillus weihenstephanensis and Bacillus cytotoxicus, was detected in 28 of 75 (37.33%) samples and 10 of 15 (66.66%) lots evaluated, with 52%, 44% and 16% of the samples of soymilk, dairy beverage of goat milk and soy protein and goat milk, respectively
Summary
Spore forming microorganisms can be present in dairy products, and they are usually associated with spoilage of milk and dairy products, especially those processed under high temperature, including powder milk, canned dairy products, goat milk, cow milk and some cheeses (Eijlander et al, 2019; Jindal & Anand, 2018; Pinto et al, 2018; Oliveira et al, 2016c; Vidal et al, 2016; Reindl et al, 2014) These microorganisms can be isolated in non-dairy products, such as soymilk, that has been increasingly consumed by lactose-intolerant people and children’s formulas. The goat milk has high dietary value and nutritional quality, and it has been highly recommended to feed children, adults and elderly people suffering from cow milk allergies, and I is being used as a substitute for dairy products by consumers with dietary restrictions (Fangmeier et al, 2019; Mituniewicz-Małek et al, 2019; Pradeep Prasanna & Charalampopoulos, 2019; Beltrán et al, 2018; Nakajima et al, 2010). Goat milk products have high added values with a growing marketing demand (Mituniewicz-Małek et al, 2019; Fonseca et al, 2013)
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