Microbiology in Dairy Processing: Challenges and Opportunities. By Palmiro Poltronieri. IFT Press Series, Wiley-Blackwell, UK, 2017; 321 pp.; ISBN: 978-1-119-11480-2 (original) (raw)
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2019
Lactobacillus delbrueckii ssp. bulgaricus, an important species of lactic acid bacteria, is widely used in the dairy industry, particularly in yogurt production. Commonly used in mixed cultures and especially with Streptococcus thermophilus, L. bulgaricus is mandatory for traditional yogurt and also confers several health benefits that meet the prerequisites for probiotic bacteria. The current standard medium, de Man, Rogosa and Sharpe (MRS), is unreliable as a selective method for isolating L. bulgarcius species from different sources including dairy products. MRS can also present a false positive for L. bulgaricus in some dairy products due to the presence of high background colonies of similar species. Consequently, there is a need for a better, more reliable medium for the differential enumeration of L. bulgaricus. The objective of this study was thus to formulate an agar medium that is effective for the differential isolation and enumeration of L. bulgaricus. A modified reinfor...
Rapid methods of microbial detection in dairy products
Food Control, 2020
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Microbiological Research on Some Dairy Products
One hundred samples of dairy products (25 each) of UHT milk, plain yoghurt, fruit yoghurt and white soft cheese samples were examined for total viable count, and the presence of foodborne pathogenic microorganisms. The results declared that the mean total bacterial counts/mL or gm were 2.9 x10 4 and 7.8 x10 4 in examined UHT milk and white soft cheese samples, respectively. Staphylococci, Enterococci, E. coli, and Clostridium perfringens were detected in (0.0, 28.0, 40.0 and 64.0 %) & (16.0, 20.0, 36.0 and 48.0 %) & (0.0, 20.0, 28.0 and 28.0 %) and (8.0, 0.0, 0.0 and 12.0 %) of examined samples, respectively. The mean values of isolated organisms/mL or gm were (0, 1.2 x10 3 , 1.3 x10 3 and 3.4 x10 3) & (1 x10 3 , 1.4 x10 3 , 1.98 x10 3 and 1.95 x10 3) & (0, 7.6 x10 2 , 2.2 x10 3 and 2.1 x10 3) and (0.9 x10 3 , 0, 0 and 3.3 x10 3), respectively. The predominant isolated bacterial stains were Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Enterococcus faecium, Enterococcus durans, E. coli, and Clostridium perfringens by frequency distribution of (0.0, 21.7, 12.9 and 20.4 %) & (0.0, 26.2, 29.0 and 26.5 %) & (28.6, 21.7, 19.4 and 10.2 %) & (42.8, 8.7, 12.9 and 14.3 %) & (0.0, 0.0, 3.2 and 8.2 %) & (0.0, 21.7, 22.6 and 14.3 %) and (28.6, 0.0, 0.0 and 6.1 %) of total isolates, respectively. Meanwhile, Campylobacter jejuni and Salmonellae failed to be detected in all examined samples. The sanitary and public health importance of these organisms as well as control measures to improve the quality of dairy products and to safeguard the consumers from infection were discussed.
2018
Chocolate milk typically has higher microbiological counts than unflavored milk and is susceptible to off-flavor development before the end of targeted shelf life. It has been suggested that the addition of multiple ingredients (chocolate, sucrose, stabilizers, and vitamin A and D) contributes to expedited growth of spoilage organisms in chocolate milk. The objective of this study was to isolate and identify the organisms responsible for off-flavor development in nonfat chocolate milk. Nonfat chocolate milk was obtained from regional fluid milk processors (3 plants). At the end of shelf life (18 d) off-odors had developed and the milk was serial diluted and spread plated on standard and differential media including tryptic soy agar, De Man, Rogosa and Sharpe agar, skim milk agar, spirit blue agar, chocolate milk agar, and MacConkey agar. Isolates were streaked on chocolate milk agar (standard methods agar with 10% vol/vol chocolate milk). Five causative isolates were selected based ...
Evolution of microbiological analytical methods for dairy industry needs
Frontiers in Microbiology, 2014
Traditionally, culture-based methods have been used to enumerate microbial populations in dairy products. Recent developments in molecular methods now enable faster and more sensitive analyses than classical microbiology procedures. These molecular tools allow a detailed characterization of cell physiological states and bacterial fitness and thus, offer new perspectives to integration of microbial physiology monitoring to improve industrial processes. This review summarizes the methods described to enumerate and characterize physiological states of technological microbiota in dairy products, and discusses the current deficiencies in relation to the industry's needs. Recent studies show that Polymerase chain reaction-based methods can successfully be applied to quantify fermenting microbes and probiotics in dairy products. Flow cytometry and omics technologies also show interesting analytical potentialities. However, they still suffer from a lack of validation and standardization for quality control analyses, as reflected by the absence of performance studies and official international standards.
A 100-Year Review: Microbiology and safety of milk handling
Journal of dairy science, 2017
Microbes that may be present in milk can include pathogens, spoilage organisms, organisms that may be conditionally beneficial (e.g., lactic acid bacteria), and those that have not been linked to either beneficial or detrimental effects on product quality or human health. Although milk can contain a full range of organisms classified as microbes (i.e., bacteria, viruses, fungi, and protozoans), with few exceptions (e.g., phages that affect fermentations, fungal spoilage organisms, and, to a lesser extent, the protozoan pathogens Cryptosporidium and Giardia) dairy microbiology to date has focused predominantly on bacteria. Between 1917 and 2017, our understanding of the microbes present in milk and the tools available for studying those microbes have changed dramatically. Improved microbiological tools have enabled enhanced detection of known microbes in milk and dairy products and have facilitated better identification of pathogens and spoilage organisms that were not known or well ...
Journal of Applied Microbiology, 2022
Traditionally, fermentation was used to preserve the shelf life of food. Currently, in addition to favouring food preservation, well standardized and controlled industrial processes are also aimed at improving the functional characteristics of the final product. In this regard, starter cultures have become an essential cornerstone of food production. The selection of robust microorganisms, well adapted to the food environment, has been followed by the development of microbial consortia that provide some functional characteristics, beyond their acidifying capacity, achieving safer, high-quality foods with improved nutritional and health-promoting properties. In addition to starters, adjunct cultures and probiotics, which normally do not have a relevant role in fermentation, are added to the food in order to provide some beneficial characteristics. This review focuses on highlighting the functional characteristics of food starters, as well as adjunct and probiotic cultures (mainly lac...
World Journal of Microbiology and Biotechnology, 2011
Raw milk used to produce Grana cheese was subjected to several treatment regimes, including varying temperatures and storage times. Milk from morning and evening milking were transferred to a dairy factory separately (double delivery) or together (single delivery), after storage at the farm for 12 h; in the former case, milk was stored at 12 or 8°C, whereas, in the latter, it was kept at ambient temperature or 18°C. Values of pH of the vat milk were lower for milk samples kept at room temperature, while other physico-chemical parameters and rheological characteristics tested did not show significant differences linked to the different storage temperatures of milk used for ''Grana Trentino'' cheese production. Total microorganisms and several microbial groups (psychrotrophic bacteria, coliforms, mesophilic and termophilic lactic acid bacteria, including enterococci, pseudomonads and clostridia) were detected and quantified by classical (plate count and most probable number) techniques, after each technological treatment for a total of 212 milk and cream samples. The application of a culture-independent microbiological strategy, consisting of denaturing gradient gel electrophoresis, allowed the recognition of several bacterial genera and species.