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)
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.
African Journal of Microbiology Research, 2012
Bacterial contamination of pasteurized milk may originate from different sources: raw milk, process equipment surfaces and packaging materials. It is hypothesized that post-pasteurization contamination along the milk processing lines is responsible of reducing shelf life of Algerian pasteurized milk. This assumption was investigated through assessment of both the microflora of biofilms in milk pipeline systems at five dairy plants of Northwestern Algeria and the effectiveness of a quaternary ammonium based compound used for the disinfection of the plant equipment. Samples were collected before and after cleaning-in-place (CIP) systems from different segments of pasteurization lines with sterile cotton swabs. Quantitative assessment showed little reduction of the total bacteria count after CIP. On the average bacterial numbers were 5.6 × 10 3 , 1.2 × 10 4 , 5.1 × 10 4 , 2.5 × 10 5 and 9.7 × 10 7 cfu/cm 2 , respectively, in the different units. Phenotypic identification of isolates revealed predominance of Gram-positive bacilli belonging to Bacillus and notably the Bacillus cereus group, at maximal levels of 72 and 21% respectively. The other Gram-positive microflora included Staphylococcus (30%) and Micrococcus (10%). In contrast, the incidence of the Gram-negative bacteria was relatively low. Two genera, identified as Pseudomonas (9%) and Enterobacter (6%), were found only in two dairies. Three dairies were Gram-negative bacteria-free. That should be the result of common contamination sources or highly environmental selective pressure. Further studies have to address these hypotheses. Treatment of experimental Bacillus cereus sensu lato strains biofilms with a 50, 100 and 150 ppm of quaternary ammonium disinfectant, showed a significant resistance of biofilms to this product even after long exposure time (15 min). This study emphasized the importance of aerobic spore-forming bacteria in dairy-processing equipment as they are able to built recalcitrant biofilms on the inside equipment surfaces with subsequent resistance to conventional CIP system and potential transfer to pasteurized milk. Therefore, in order to reduce the contamination levels of spore-forming bacteria and improve the quality and shelf life of the product, these dairies have, besides improvement in the hygienic status of the plant equipments, also to monitor either the pasteurization process or the contamination from raw material (that is, milk powder).
Bacterial Contamination of Dairy Products
Food plays a vital role in our daily life. Globally, billions of people consume milk and dairy products every day. Milk and milk products have great nutritional qualities and hence, their consumption is increasing worldwide. Due to its highly nutritious nature of the milk and dairy products, it serves as an excellent growth medium for a wide range of microbes. Microbial contamination of milk and dairy products is a universal problem. Foodborne microbial diseases account for 20 million cases annually in the world. In the last two decades, foodborne illnesses from consumption of dairy products have been mainly implicated with Campylobacter jejuni, Escherichia coli 0157:H7, Listeria monocytogenes, and Salmonella entertica. The spoilage of milk products is an enormous economic problem worldwide. The microbial load and incidence of the bacterial pathogens in foods are indicators of food quality. Many of the microbiological hazards associated with dairy products such as butter, cheese, and yoghurt are derived from the raw milk. Pathogen like Staphylococcus aureus may be part of the resident microflora of the living animal, where as other pathogens such as Escherichia coli 0157:H7 or Salmonella spp. may originate from faecal contamination during initial milk collection. It can also be subjected to contamination during transport, storage and manufacturing processes. Preventing post process contamination by spoilage microorganisms and retarding the growth of surviving organisms remain a challenge to the dairy industry. Therefore, increased emphasis should be placed on the microbiological examination of milk and dairy foods. It is emphasized that milk should be properly pasteurized and adequate hygienic measures should be adopted during the preparation of dairy products. In addition, the education of food handlers about personal hygiene is of pivotal importance from food safety point of view.
Novel insights into the microbiology of fermented dairy foods
Fermentation is a traditional approach to food preservation that, in addition to improving food safety, also confers enhanced organoleptic, nutritional, and health-promoting attributes upon those foods. Dairy products can be fermented by a diverse microbiota. The accompanying microbes can be studied using a variety of different, including ‘omics’-based, approaches that can reveal their composition and functionality. These methods have increasingly been recently applied to study fermented dairy foods from the perspective of genetic diversity, functionality and succession. The insights provided by these studies are summarised in this review.
Food biotechnology applications in dairy and dairy products
Journal of Pharmacy Research, 2018
Biotechnological achievements of recent years have emerged as powerful tool to develop quality attributes of livestock products include dairy and dairy-based products. Biotechnology has applied to food processing in most developing countries makes use of microbial inoculants to enhance properties such as the taste, aroma, shelf-life, consistency, and nutritional value of foods/dairy products. Probiotic food products are a rapidly growing area of functional food, as found to be robustly accepted by the consumers. However, the food industry is looking for to produce diverse varieties of probiotic foods other than dairy products with prospective health benefits. In this review, the broad array of available dairy foods, by-product waste utilization of dairy and dairy processing challenges the microbiologist, engineer and technologist to find the best ways to prevent the entry of microorganisms, destroy those that do get in along with their enzymes and prevent the growth and activities o...
Characterization of the lactic acid bacteria in artisanal dairy products
Journal of Dairy Research, 1997
S. In all, 4379 isolates from 35 products, including 24 artisanal cheeses, were surveyed with a view to identifying strains that could be used as starters in commercial dairy fermentations. Of the isolates, 38 % were classified as Lactococcus, 17 % as Enterococcus, 14% as Streptococcus thermophilus, 12 % as mesophilic Lactobacillus, 10% as Leuconostoc and 9 % as thermophilic Lactobacillus. Acid production by the isolates varied considerably. Of the 1582 isolates of Lactococcus and 482 isolates of mesophilic Lactobacillus tested, only 8 and 2 % respectively produced sufficient acid to lower the pH of milk to 5n3 in 6 h at 30 mC. In contrast, 53, 32 and 13 % of Str. thermophilus, thermophilic Lactobacillus and Enterococcus isolates respectively reduced the pH to 5n3. These isolates were found only in some French, Italian and Greek cheeses. Bacteriocins were produced by 11 % of the 2257 isolates tested and 26 of them produced broad-spectrum bacteriocins which inhibited at least eight of the ten target strains used, which included lactic acid bacteria, clostridia and Listeria innocua. The most proteolytic of the 2469 isolates tested were
2018
Agri-food industriesmust guarantee the safety of the produced foods through the application of the existing regulations, by correctly implementing quality control systems. In relation to the quality of drinking milk, it is extremely important to monitor the industrial treatments to which it is subjected to avoid the multiplication of spoilage and pathogenic microorganisms. Raw milk must undergo strict quality controls at the primary production level based on the knowledge of themain factors that influence their quality andmicrobiological safety: hygienic practices, health status of cows, frequency andmoment of collection, storage temperature and time of transportation. To improve food safety and estimate food shelf life, predictive microbiology is a widely used tool for the estimation of microbial behavior as a function of intrinsic and extrinsic by using mathematical models. Throughout this chapter, a description of the current food quality management systems (FQMS) carried out by ...