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Zarei M, Elmi Anvari S, Maktabi S, Saris PEJ, Yousefvand A. Identification, proteolytic activity quantification and biofilm-forming characterization of Gram-positive, proteolytic, psychrotrophic bacteria isolated from cold raw milk. PLoS One 2023; 18:e0290953. [PMID: 37703270 PMCID: PMC10499245 DOI: 10.1371/journal.pone.0290953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Accepted: 08/19/2023] [Indexed: 09/15/2023] Open
Abstract
Psychrotrophic bacteria of raw milk face the dairy industry with significant spoilage and technological problems due to their ability to produce heat-resistant enzymes and biofilms. Despite extensive information about Gram-negative psychrotrophic bacteria in milk, little is known about Gram-positive psychrotrophic bacteria in milk, and their proteolytic activity and biofilm-forming characteristics. In the present study, Gram-positive, proteolytic, psychrotrophic bacteria of cold raw milk were identified, and their proteolytic activity and biofilm-forming capacity were quantified. In total, 12 genera and 22 species were represented among the bacterial isolates, however 50% belonged to three genera, namely Staphylococcus (19.4%), Bacillus (16.7%), and Enterococcus (13.9%). Different levels of proteolytic activity were detected in the identified isolates, even among the strains belonging to the same species. In addition, proteolytic activity was significantly higher at 25°C than at 7°C for all isolates. The crystal violet staining assay in polystyrene microtitre plates revealed a high level of variation in the biofilm-forming capacity at 7°C. After 72 hours of incubation, 11.1% of the strains did not produce a biofilm, while 27.8%, 52.8%, and 8.3% produced low, moderate, and high amounts of biofilm on polystyrene, respectively. The psychrotrophic bacteria were also able to produce biofilms on the surface of stainless steel coupons in ultra-high temperature milk after 72 h of incubation at 7°C; the number of attached cells ranged from 1.34 to 5.11 log cfu/cm2. These results expand the knowledge related to the proteolytic activity and biofilm-forming capacity of Gram-positive psychrotrophic milk bacteria.
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Affiliation(s)
- Mehdi Zarei
- Department of Food Hygiene, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran
| | - Sahar Elmi Anvari
- Department of Food Hygiene, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran
| | - Siavash Maktabi
- Department of Food Hygiene, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran
| | - Per Erik Joakim Saris
- Department of Microbiology, Faculty of Agriculture and Forestry, University of Helsinki, Helsinki, Finland
| | - Amin Yousefvand
- Department of Microbiology, Faculty of Agriculture and Forestry, University of Helsinki, Helsinki, Finland
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Moreira IMFB, da Silva Rodrigues R, Machado SG, de Carvalho AF. Phylogenetic characterization and biodiversity of spore-forming bacteria isolated from Brazilian UHT milk. Braz J Microbiol 2023; 54:2153-2162. [PMID: 37495831 PMCID: PMC10484864 DOI: 10.1007/s42770-023-01063-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 07/05/2023] [Indexed: 07/28/2023] Open
Abstract
Among the milk contaminating microorganisms, those which are able to form heat-resistant spores are concerning, especially for dairy companies that use ultra-high temperature (UHT) technology. These spores, throughout storage, can germinate and produce hydrolytic enzymes that compromise the quality of the final product. This study evaluated 184 UHT milk samples from different batches collected from seven Brazilian dairy companies with a possible microbial contamination problem. The bacteria were isolated, phenotypically characterized, clustered by REP-PCR, and identified through 16S rDNA sequencing. The presence of Bacillus sporothermodurans was verified using biochemical tests (Gram staining, catalase and oxidase test, glucose fermentation, esculin hydrolysis, nitrate reduction, and urease test). According to these tests, none of the isolates presented typical characteristics of B. sporothermodurans. In sequence, the isolates, that presented rod-shapes, were submitted to molecular analyses in order to determine the microbial biodiversity existing among them. The isolates obtained were grouped into 16 clusters, four of which were composed of only one individual. A phylogenetic tree was constructed using the sequences obtained from the 16S rDNA sequencing and some reference strains of species close to those found using BLAST search in the NCBI nucleotide database. Through this tree, it was possible to verify the division of the isolates into two large groups, the Bacillus subtilis and the Bacillus cereus groups. Furthermore, most isolates are phylogenetically closely related, which makes it even more difficult to identify them at the species level. In conclusion, it was possible to assess, in general, the groups of sporulated contaminants in Brazilian UHT milk produced in the regions evaluated. In addition, it was also possible to determine the biodiversity of spore-forming bacteria found in UHT milk samples, thus opening up a range of possible research topics regarding the effects of the presence of these microorganisms on milk quality.
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Affiliation(s)
- Isabella Maria Fernandes Botelho Moreira
- InovaLeite - Laboratório de Pesquisa em Leites e Derivados, Departamento de Tecnologia de Alimentos, Universidade Federal de Viçosa, Viçosa, MG, 36570 900, Brazil
| | - Rafaela da Silva Rodrigues
- InovaLeite - Laboratório de Pesquisa em Leites e Derivados, Departamento de Tecnologia de Alimentos, Universidade Federal de Viçosa, Viçosa, MG, 36570 900, Brazil
- InsPOA - Laboratório de Inspeção de Produtos de Origem Animal, Departamento de Veterinária, Universidade Federal de Viçosa, Viçosa, MG, 36570 900, Brazil
| | - Solimar Gonçalves Machado
- InovaLeite - Laboratório de Pesquisa em Leites e Derivados, Departamento de Tecnologia de Alimentos, Universidade Federal de Viçosa, Viçosa, MG, 36570 900, Brazil
| | - Antônio Fernandes de Carvalho
- InovaLeite - Laboratório de Pesquisa em Leites e Derivados, Departamento de Tecnologia de Alimentos, Universidade Federal de Viçosa, Viçosa, MG, 36570 900, Brazil.
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3
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Sun Y, Wang R, Li Q, Ma Y. Influence of storage time on protein composition and simulated digestion of UHT milk and centrifugation presterilized UHT milk in vitro. J Dairy Sci 2023; 106:3109-3122. [PMID: 37002142 DOI: 10.3168/jds.2022-22602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Accepted: 12/06/2022] [Indexed: 03/31/2023]
Abstract
The centrifugation presterilizing UHT (C-UHT) sterilization method removes 90% of the microorganism and somatic cells from raw milk using high-speed centrifugation following UHT treatment. This study aimed to study the changes in protein composition and plasmin in the UHT and C-UHT milk. The digestive characteristics, composition, and peptide spectrum of milk protein sterilized with the 2 technologies were studied using a dynamic digestive system of a simulated human stomach. The Pierce bicinchoninic acid assay, laser scanning confocal microscope, liquid chromatography-tandem mass spectrometry, and AA analysis were used to study the digestive fluid at different time points of gastric digestion in vitro. The results demonstrated that C-UHT milk had considerably higher protein degradation than UHT milk. Different processes resulted during the cleavage of milk proteins at different sites during digestion, resulting in different derived peptides. The results showed there was no significant effect of UHT and C-UHT on the peptide spectrum of milk proteins, but C-UHT could release relatively more bioactive peptides and free AA.
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Affiliation(s)
- Yue Sun
- Department of Food Nutrition and Health, School of Medicine and Nutrition, Harbin Institute of Technology, Harbin, China, 150001
| | - Rongchun Wang
- Department of Food Nutrition and Health, School of Medicine and Nutrition, Harbin Institute of Technology, Harbin, China, 150001; Zhengzhou Institute, Harbin Institute of Technology, Zhengzhou, China, 450001.
| | - Qiming Li
- New Hope Dairy Co. Ltd., Chengdu, Sichuan, China, 610063; Dairy Nutrition and Function, Key Laboratory of Sichuan Province, Chengdu, China, 610000
| | - Ying Ma
- Department of Food Nutrition and Health, School of Medicine and Nutrition, Harbin Institute of Technology, Harbin, China, 150001; Zhengzhou Institute, Harbin Institute of Technology, Zhengzhou, China, 450001
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4
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Du B, Meng L, Liu H, Zheng N, Zhang Y, Zhao S, Li M, Wang J. Diversity and proteolytic activity of Pseudomonas species isolated from raw cow milk samples across China. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 838:156382. [PMID: 35660435 DOI: 10.1016/j.scitotenv.2022.156382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 05/27/2022] [Accepted: 05/27/2022] [Indexed: 06/15/2023]
Abstract
Pseudomonas spp. are common microorganisms from cold-storage raw milk, and protease secreted by Pseudomonas spp. can cause the deterioration of stored milk. However, analyses of Pseudomonas spp. diversity and proteolytic activity in raw milk from different regions of China have not been extensively examined. With this aim, the diversity and proteolytic activity of Pseudomonas isolated from 25 raw cow milk samples from Inner Mongolia, Heilongjiang, Gansu, Henan, Anhui, Jiangsu, Chongqing and Hunan of China in different seasons were evaluated by PCR targeting 16S rDNA and rpoD, as well as TNBS method, respectively. A total of 116 Pseudomonas isolates from 25 raw cow milk samples were identified at the species level, including P. fluorescens, P. veronii, P. psychrophila, P. lundensis, P. lactis, P. azotoformans, P. granadensis, P. lurida, P. rhizosphaerae, P. rhodesiae and P. extremorientalis. P. fluorescens accounted for 75.8% of the total. Of all 116 Pseudomonas isolates, 68.9% of them displayed proteolytic activity at 4 °C, 81.9% at 10 °C and 85.3% at 25 °C, respectively. The aprX gene encoded a secreted and heat-resistant metalloprotease that was present in 60.3% of the Pseudomonas isolates tested. The proteases showed residual activity ranged from 73 ± 4% to 84 ± 7% residual activity after the heat treatment at 72 °C for 15 s and 62 ± 3% to 74 ± 2% after the heat treatment at 132 °C for 4 s. This is the first report to compare Pseudomonas spp. diversity and proteolytic activity at species levels in raw milk from different regions of China. The results of this study provide valuable data about the diversity and spoilage potential of Pseudomonas species in raw milk and the thermal resistance of the proteases. Therefore, these findings provide a reference for the importance to prevent Pseudomonas spp. contamination of raw cow milk to ensure the quality and safety of milk and dairy products.
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Affiliation(s)
- Bingyao Du
- Key Laboratory of Quality & Safety Control for Milk and Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; State Key Laboratory of Grassland Agro-Ecosystems, Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture and Rural Affairs, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730020, China; Laboratory of Quality and Safety Risk Assessment for Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Lu Meng
- Key Laboratory of Quality & Safety Control for Milk and Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; Laboratory of Quality and Safety Risk Assessment for Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Huimin Liu
- Key Laboratory of Quality & Safety Control for Milk and Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; Laboratory of Quality and Safety Risk Assessment for Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Nan Zheng
- Key Laboratory of Quality & Safety Control for Milk and Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; Laboratory of Quality and Safety Risk Assessment for Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Yangdong Zhang
- Key Laboratory of Quality & Safety Control for Milk and Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; Laboratory of Quality and Safety Risk Assessment for Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Shengguo Zhao
- Key Laboratory of Quality & Safety Control for Milk and Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; Laboratory of Quality and Safety Risk Assessment for Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Ming Li
- Key Laboratory of Quality & Safety Control for Milk and Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; Laboratory of Quality and Safety Risk Assessment for Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Jiaqi Wang
- Key Laboratory of Quality & Safety Control for Milk and Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China; Laboratory of Quality and Safety Risk Assessment for Dairy Products of Ministry of Agriculture and Rural Affairs, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
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Biochemical, microbiological, and structural evaluations to early detect age gelation of milk caused by proteolytic activity of Pseudomonas fluorescens. Eur Food Res Technol 2022. [DOI: 10.1007/s00217-022-04033-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AbstractHeat–stable peptidase AprX, released by Pseudomonas species in raw milk during cold storage, can cause gelation of UHT milk since it is able to split caseinomacropeptides (CMPtot) from κ-casein, so inducing aggregation of casein micelles. Identifying raw milk susceptibility to gelation would allow UHT milk manufacturers to select appropriate processing conditions or give the milk a different destination. Two approaches, i.e., detection of free CMPtot and evidence of casein aggregates, were evaluated as possible indicators for early detecting milk destabilization. With this aim, microfiltered milk was inoculated with a P. fluorescence strain and incubated at either 4 or 25 °C. The presence of CMPtot was detected using capillary electrophoresis after 96 and 24 h at the two temperatures, respectively, when milk also became heat unstable and small flocks of protein appeared. Confocal laser scanning microscopy evidenced initial aggregates of casein micelles after 48 and 24 h at 4 and 25 °C, respectively. Keeping the milk at 25 °C/24 h could be a useful condition to accelerate milk destabilization. Despite the similar timing of instability detection, presence of CMPtot was the only trait specific for AprX activity.
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Andrewes P. Predicting the shelf-life of microbially-stabilised dairy products: What are the roles of stability studies, storage trials, ‘accelerated’ trials, and dairy science? Int Dairy J 2022. [DOI: 10.1016/j.idairyj.2021.105239] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Morandi S, Pica V, Masotti F, Cattaneo S, Brasca M, De Noni I, Silvetti T. Proteolytic Traits of Psychrotrophic Bacteria Potentially Causative of Sterilized Milk Instability: Genotypic, Phenotypic and Peptidomic Insight. Foods 2021; 10:foods10050934. [PMID: 33923137 PMCID: PMC8145555 DOI: 10.3390/foods10050934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 04/15/2021] [Accepted: 04/22/2021] [Indexed: 11/16/2022] Open
Abstract
The proteolytic traits of the psychrotrophic strains Pseudomonas poae LP5, Pseudomonas fluorescens LPF3, Chryseobacterium joostei LPR1, Pseudomonas fulva PS1, Citrobacter freundii PS37, Hafnia alvei PS46, and Serratia marcescens PS92 were initially investigated by phenotypic and genotypic approaches. Six strains elicited extracellular proteolytic activity, and five expressed the thermostable AprX or (likely) Ser1 enzymes. Then, the strains were inoculated (104 CFU/mL) in microfiltered pasteurized milk and kept at 4 °C for five days. All of the strains reached 108 CFU/mL at the end of storage and five produced thermostable extracellular proteolytic enzymes. The freshly inoculated samples and the corresponding samples at 108 CFU/mL were batch-sterilized (131 °C, 30 s) and kept at 45 °C up to 100 days. The former samples did not gel until the end of incubation, whereas the latter, containing P. poae, P. fluorescens, C. joostei, C. freundii, and S. marcescens, gelled within a few days of incubation. The thermostable proteolytic activity of strains affected the peptidomic profile, and specific proteolyzed zones of β-CN were recognized in the gelled samples. Overall, the results confirm some proteolytic traits of psychrotrophic Pseudomonas spp. strains and provide additional insights on the proteolytic activity of psychrotrophic bacteria potentially responsible for sterilized milk destabilization.
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Affiliation(s)
- Stefano Morandi
- National Research Council, Institute of Sciences of Food Production, Via G. Celoria 2, 20133 Milan, Italy; (S.M.); (M.B.); (T.S.)
| | - Valentina Pica
- Department of Food, Environmental and Nutritional Sciences, Università degli Studi di Milano, Via G. Celoria 2, 20133 Milan, Italy; (V.P.); (F.M.); (S.C.)
| | - Fabio Masotti
- Department of Food, Environmental and Nutritional Sciences, Università degli Studi di Milano, Via G. Celoria 2, 20133 Milan, Italy; (V.P.); (F.M.); (S.C.)
| | - Stefano Cattaneo
- Department of Food, Environmental and Nutritional Sciences, Università degli Studi di Milano, Via G. Celoria 2, 20133 Milan, Italy; (V.P.); (F.M.); (S.C.)
| | - Milena Brasca
- National Research Council, Institute of Sciences of Food Production, Via G. Celoria 2, 20133 Milan, Italy; (S.M.); (M.B.); (T.S.)
| | - Ivano De Noni
- Department of Food, Environmental and Nutritional Sciences, Università degli Studi di Milano, Via G. Celoria 2, 20133 Milan, Italy; (V.P.); (F.M.); (S.C.)
- Correspondence:
| | - Tiziana Silvetti
- National Research Council, Institute of Sciences of Food Production, Via G. Celoria 2, 20133 Milan, Italy; (S.M.); (M.B.); (T.S.)
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Luo Q, Zhong Z, Zheng Y, Gao D, Xia Z, Wang L. Preparation and evaluation of a poly(N-isopropylacrylamide) derived graphene quantum dots based hydrophilic interaction and reversed-phase mixed-mode stationary phase for complex sample analysis. Talanta 2021; 224:121869. [DOI: 10.1016/j.talanta.2020.121869] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 10/28/2020] [Accepted: 11/03/2020] [Indexed: 11/27/2022]
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9
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Porcellato D, Smistad M, Bombelli A, Abdelghani A, Jørgensen HJ, Skeie SB. Longitudinal Study of the Bulk Tank Milk Microbiota Reveals Major Temporal Shifts in Composition. Front Microbiol 2021; 12:616429. [PMID: 33708181 PMCID: PMC7940241 DOI: 10.3389/fmicb.2021.616429] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 02/04/2021] [Indexed: 01/04/2023] Open
Abstract
Introduction of microbial contaminations in the dairy value chain starts at the farm level and the initial microbial composition may severely affect the production of high-quality dairy products. Therefore, understanding the farm-to-farm variation and longitudinal shifts in the composition of the bulk tank milk microbiota is fundamental to increase the quality and reduce the spoilage and waste of milk and dairy products. In this study, we performed a double experiment to study long- and short-term longitudinal shifts in microbial composition using 16S rRNA gene amplicon sequencing. We analyzed milk from 37 farms, that had also been investigated two years earlier, to understand the stability and overall microbial changes over a longer time span. In addition, we sampled bulk tank milk from five farms every 1–2 weeks for up to 7 months to observe short-term changes in microbial composition. We demonstrated that a persistent and farm-specific microbiota is found in bulk tank milk and that changes in composition within the same farm are mostly driven by bacterial genera associated with mastitis (e.g., Staphylococcus and Streptococcus). On a long-term, we detected that major shift in milk microbiota were not correlated with farm settings, such as milking system, number of cows and quality of the milk but other factors, such as weather and feeding, may have had a greater impact on the main shifts in composition of the bulk tank milk microbiota. Our results provide new information regarding the ecology of raw milk microbiota at the farm level.
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Affiliation(s)
- Davide Porcellato
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, NMBU, Ås, Norway
| | - Marit Smistad
- Norwegian Veterinary Institute, Oslo, Norway.,TINE SA, Oslo, Norway
| | - Alberto Bombelli
- Department of Agrotechnology and Food Science, Wageningen University and Research, Wageningen, Netherlands
| | - Ahmed Abdelghani
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, NMBU, Ås, Norway
| | - Hannah Joan Jørgensen
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, NMBU, Ås, Norway
| | - Siv B Skeie
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, NMBU, Ås, Norway
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Martin NH, Torres-Frenzel P, Wiedmann M. Invited review: Controlling dairy product spoilage to reduce food loss and waste. J Dairy Sci 2020; 104:1251-1261. [PMID: 33309352 DOI: 10.3168/jds.2020-19130] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Accepted: 09/16/2020] [Indexed: 01/30/2023]
Abstract
Food loss and waste is a major concern in the United States and globally, with dairy foods representing one of the top categories of food lost and wasted. Estimates indicate that in the United States, approximately a quarter of dairy products are lost at the production level or wasted at the retail or consumer level annually. Premature microbial spoilage of dairy products, including fluid milk, cheese, and cultured products, is a primary contributor to dairy food waste. Microbial contamination may occur at various points throughout the production and processing continuum and includes organisms such as gram-negative bacteria (e.g., Pseudomonas), gram-positive bacteria (e.g., Paenibacillus), and a wide range of fungal organisms. These organisms grow at refrigerated storage temperatures, often rapidly, and create various degradative enzymes that result in off-odors, flavors, and body defects (e.g., coagulation), rendering them inedible. Reducing premature dairy food spoilage will in turn reduce waste throughout the dairy continuum. Strategies to reduce premature spoilage include reducing raw material contamination on-farm, physically removing microbial contaminants, employing biocontrol agents to reduce outgrowth of microbial contaminants, tracking and eliminating microbial contaminants using advanced molecular microbiological techniques, and others. This review will address the primary microbial causes of premature dairy product spoilage and methods of controlling this spoilage to reduce loss and waste in dairy products.
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Affiliation(s)
- N H Martin
- Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, NY 14853.
| | - P Torres-Frenzel
- Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, NY 14853
| | - M Wiedmann
- Milk Quality Improvement Program, Department of Food Science, Cornell University, Ithaca, NY 14853
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Identification, phylogenetic characterisation and proteolytic activity quantification of high biofilm-forming Pseudomonas fluorescens group bacterial strains isolated from cold raw milk. Int Dairy J 2020. [DOI: 10.1016/j.idairyj.2020.104787] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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12
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Identification of Pseudomonas jessenii and Pseudomonas gessardii as the most proteolytic Pseudomonas isolates in Iranian raw milk and their impact on stability of sterilized milk during storage. J DAIRY RES 2020; 87:368-374. [PMID: 32893770 DOI: 10.1017/s0022029920000709] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Identification of the most proteolytic Pseudomonas strains that can produce heat-resistant proteases and contribute to the Ultra High Temperature (UHT) milk destabilization is of great interest. In the present study, among the 146 Pseudomonas isolates that encoded the aprX gene, five isolates with the highest proteolytic activity were selected and identified based on 16S rRNA, rpoD and gyrB gene sequences data. The identification results were confirmed by phylogenetic analysis based on multilocus sequence analysis and identified the representative isolates as P. jessenii (two isolates) and P. gessardii (three isolates). Casein zymography demonstrated the ability of these species to produce heat-resistant enzymes, AprX, with molecular mass of about 48 kDa during storage at 7° C for 72 h. In sterilized milk samples, the residual activity of AprX caused a considerable enhancement in the degree of protein hydrolysis, non-protein nitrogen and non-casein nitrogen contents of the samples during a two-month storage. This enhancement was slightly higher in samples containing enzyme produced by P. jessenii compared to P. gessardii ones, resulting in earlier onset of sterilized milk destabilization. Hence, this study revealed that P. jessenii and P. gessardii can play a considerable role in deterioration of Iranian commercial long-life milk.
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