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Giagnoni L, Deb S, Tondello A, Zardinoni G, De Noni M, Franchin C, Vanzin A, Arrigoni G, Masi A, Stevanato P, Cecchinato A, Squartini A, Spanu C. The impact of milk storage temperatures on cheese quality and microbial communities at dairy processing plant scale. Food Res Int 2023; 172:113101. [PMID: 37689865 DOI: 10.1016/j.foodres.2023.113101] [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: 02/14/2023] [Revised: 05/11/2023] [Accepted: 06/09/2023] [Indexed: 09/11/2023]
Abstract
Cheese production is an applied biotechnology whose proper outcome relies strictly on the complex interactive dynamics which unfold within defined microbial groups. These may start being active from the collection of milk and continue up to its final stages of maturation. One of the critical parameters playing a major role is the milk refrigeration temperature before pasteurization as it can affect the proportion of psychrotrophic taxa abundance in the total milk bacterial population. While a standard temperature of 4 °C is the common choice, due to its general growth control effect, it does have a potential drawback. This is due to the fact that some cold-tolerant genera present a proteolytic activity with uncompleted proliferation, which could negatively affect curd clotting and regular cheese maturation. Moreover, accidental thermal variations of milk before cheese-making, in a plus or minus direction, can occur both at farm collection sites and during transfer to dairy plant. This present research, directly commissioned by a major fresh cheese-producing company, includes an in-factory trial. In this trial, a gradient of temperatures from 4 °C to 13 °C, which were subsequently reversed, was purposely adopted to: (a) verify sensory alterations in the resulting product at different maturation stages, and, (b) analyze, in parallel, using DNA extraction and 16S-metabarcoding sequencing from the same samples, the presence, abundance and corresponding taxonomical identity of all the bacteria featured in communities found in milk and cheese samples. Overall, 1,714 different variants were detected and sorted into 394 identified taxa. Significant bacterial community shifts in cheese were observed in response to milk refrigeration temperature and subsequently associated with samples having altered scores in sensory panel tests. In particular, proteolytic psychrotrophes were outcompeted by Enterobacteriales and by other taxa at the peak temperature of 13 °C, but aggressively increased in the descent phases, upon the cooling down of milk to values of 7 °C. Relevant clues have been collected for better anticipation of thermal abuse effects or parameter variations allowing for improved handling of technical processing conditions by the cheese manufacturing industry.
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Affiliation(s)
- Lucia Giagnoni
- Department of Veterinary Medicine, University of Sassari, Via Vienna, 2, 07100 Sassari (SS), Italy; Department of Agronomy, Food, Natural Resources, Animals and Environment, DAFNAE, University of Padova, Viale dell'Università 16, 35020 Legnaro, (PD), Italy.
| | - Saptarathi Deb
- Department of Agronomy, Food, Natural Resources, Animals and Environment, DAFNAE, University of Padova, Viale dell'Università 16, 35020 Legnaro, (PD), Italy
| | - Alessandra Tondello
- Department of Agronomy, Food, Natural Resources, Animals and Environment, DAFNAE, University of Padova, Viale dell'Università 16, 35020 Legnaro, (PD), Italy
| | - Giulia Zardinoni
- Department of Agronomy, Food, Natural Resources, Animals and Environment, DAFNAE, University of Padova, Viale dell'Università 16, 35020 Legnaro, (PD), Italy
| | - Michele De Noni
- Latteria Montello S.p.A. Via Fante d'Italia 26, 31040 Giavera del Montello (TV), Italy
| | - Cinzia Franchin
- Department of Agronomy, Food, Natural Resources, Animals and Environment, DAFNAE, University of Padova, Viale dell'Università 16, 35020 Legnaro, (PD), Italy
| | - Alice Vanzin
- Department of Agronomy, Food, Natural Resources, Animals and Environment, DAFNAE, University of Padova, Viale dell'Università 16, 35020 Legnaro, (PD), Italy
| | - Giorgio Arrigoni
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 587b, 35131 Padova (PD), Italy
| | - Antonio Masi
- Department of Agronomy, Food, Natural Resources, Animals and Environment, DAFNAE, University of Padova, Viale dell'Università 16, 35020 Legnaro, (PD), Italy
| | - Piergiorgio Stevanato
- Department of Agronomy, Food, Natural Resources, Animals and Environment, DAFNAE, University of Padova, Viale dell'Università 16, 35020 Legnaro, (PD), Italy
| | - Alessio Cecchinato
- Department of Agronomy, Food, Natural Resources, Animals and Environment, DAFNAE, University of Padova, Viale dell'Università 16, 35020 Legnaro, (PD), Italy
| | - Andrea Squartini
- Department of Agronomy, Food, Natural Resources, Animals and Environment, DAFNAE, University of Padova, Viale dell'Università 16, 35020 Legnaro, (PD), Italy
| | - Carlo Spanu
- Department of Veterinary Medicine, University of Sassari, Via Vienna, 2, 07100 Sassari (SS), Italy
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Martínez-Robles S, González-Ballesteros E, Reyes-Esparza J, Trejo-Teniente I, Jaramillo-Loranca BE, Téllez-Jurado A, Vázquez-Valadez VH, Angeles E, Vargas Hernández G. Effect of β - hydroxy - γ -aminophosphonate (β - HPC) on the hydrolytic activity of Nocardia brasiliensis as determined by FT-IR spectrometry. Front Microbiol 2023; 14:1089156. [PMID: 36778890 PMCID: PMC9909415 DOI: 10.3389/fmicb.2023.1089156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Accepted: 01/09/2023] [Indexed: 01/27/2023] Open
Abstract
The use of immunomodulatory and metabolic modulating drugs has been considered a better strategy to improve the efficacy of conventional treatments against pathogens and metabolic diseases. L-carnitine is relevant in fatty acid metabolism and energy production by β-oxidation, but it also has a beneficial therapeutic immunomodulatory effect. The β-hydroxy-γ-aminophosphonate (β-HPC) was developed, synthesized and studied in different pathologies as a more soluble and stable analog than L-carnitine, which has been studied in bacterial physiology and metabolism; therefore, we set out to investigate the direct effect of β-HPC on the metabolism of N. brasiliensis, which causes actinomycetoma in Mexico and is underdiagnosed. To analyze the effect of β-HPC on the metabolic capacity of the bacterium for the hydrolysis of substrate casein, L-tyrosine, egg yolk, and tween 80, Fourier transform infrared spectroscopy (FT-IR) was employed. It was found that β-HPC increases the metabolic activity of N. brasiliensis associated with increased growth and increased hydrolysis of the substrates tested. By the effect of β-HPC, it was observed that, in the hydrolysis of L-tyrosine, the aromatic ring and functional groups were degraded. At 1515 cm-1, any distinctive signal or peak for this amino acid was missing, almost disappearing at 839, 720, 647, and 550 cm-1. In casein, hydrolysis is enhanced in the substrate, which is evident by the presence of NH, OH, amide, and CO. In casein, hydrolysis is enhanced in the substrate, which is evident by the presence of NH, OH, amide, COO, and P = O signals, characteristic of amino acids, in addition to the increase of the amide I and II bands. In Tween 80 the H-C = and C = C signals disappear and the ether signals are concentrated, it was distinguished by the intense band at 1100 cm-1. Egg yolk showed a large accumulation of phosphate groups at 1071 cm-1, where phosvitin is located. FT-IR has served to demonstrate that β-HPC is a hydrolysis enhancer. Furthermore, by obtaining the spectrum of N. brasiliensis, we intend to use it as a quick comparison tool with other spectra related to actinobacteria. Eventually, FT-IR may serve as a species identification option.
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Affiliation(s)
- Sandra Martínez-Robles
- Departamento de Ciencias Biológicas, Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Cuautitlán Izcalli, Mexico,Programa Educativo del Posgrado en Biotecnología, Universidad Politécnica de Pachuca, Zempoala, Mexico,*Correspondence: Sandra Martínez-Robles,
| | - Erik González-Ballesteros
- Departamento de Ciencias Biológicas, Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Cuautitlán Izcalli, Mexico
| | - Jorge Reyes-Esparza
- Facultad de Farmacia, Universidad Autónoma del Estado de Morelos, Cuernavaca, Mexico
| | - Isaí Trejo-Teniente
- Programa Educativo del Posgrado en Biotecnología, Universidad Politécnica de Pachuca, Zempoala, Mexico
| | | | - Alejandro Téllez-Jurado
- Programa Educativo del Posgrado en Biotecnología, Universidad Politécnica de Pachuca, Zempoala, Mexico
| | - Víctor H. Vázquez-Valadez
- Departamento de Ciencias Biológicas, Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Cuautitlán Izcalli, Mexico
| | - Enrique Angeles
- Departamento de Ciencias Biológicas, Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Cuautitlán Izcalli, Mexico
| | - Genaro Vargas Hernández
- Programa Educativo del Posgrado en Biotecnología, Universidad Politécnica de Pachuca, Zempoala, Mexico,Genaro Vargas Hernández,
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Felipus NC, Bajaluk SAB, Thaler Neto A, Knob DA, Alessio DRM. Quality of refrigerated raw milk according to the bulk transport conditions. ACTA SCIENTIARUM: ANIMAL SCIENCES 2022. [DOI: 10.4025/actascianimsci.v45i1.58353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023] Open
Abstract
Technical regulations that determine milk quality standards in Brazil establish the minimum criteria that the processing industry's raw material must present. These rules can challenge the logistics sector (transport) to maintain adequate milk conservation levels. We aimed to evaluate the influence of bulk transport and storage conditions on refrigerated raw milk quality. The experiment was carried out in a dairy industry in Santa Catarina State. Information and samples of refrigerated raw milk were collected from dairy farms, from isothermal compartments of milk trucks, and from the industry's storage silo. These samples were submitted to microbiological analysis, somatic cell count (SCC), and physicochemical analysis. The results were evaluated by ANOVA and multivariate analysis (factor analysis). The transport of raw milk in bulk and the transfer of raw material to the industrial silo worsened the milk's microbiological quality (p < 0.0001) for standard plate count (SPC) and psychrotrophic microorganism count (PMC), without affecting, the physicochemical characteristics of the milk (p > 0.05). Poor hygienic conditions in milk storage rooms, in the refrigeration bulk tanks of the dairy farms, and during the transport, as well as the transport on longer routes, were related to higher SPC and psychrotrophic count while receiving milk by the dairy industry with higher temperatures was only associated with higher SPC.
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Felipus NC, Thaler Neto A, Bajaluk SAB, Voges JG, Knob DA. Short communication: psychrotrophic microorganism count in raw milk samples preserved with azidiol®. ACTA SCIENTIARUM: ANIMAL SCIENCES 2022. [DOI: 10.4025/actascianimsci.v45i1.58349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023] Open
Abstract
The study aimed to evaluate the use of the azidiol® preservative for psychrotrophic microorganism count (PMC) in cooled raw milk. Two studies were carried out, one under controlled conditions (experiment 1) and the other under field conditions (experiment 2), in which samples of raw milk were taken with and without the use of the azidiol® preservative and analyzed at predefined times (0, 6, 12 and 24 hours - experiment 1) and at varying times (experiment 2). Analysis of variance and regression analysis using SAS were applied for data statistical analysis. Milk samples without azidiol® showed higher PMC with increasing time between sampling and analysis, while in samples preserved with azidiol®, this count remained constant. Samples of cooled raw milk intended for PMC should be collected in flasks containing the azidiol® preservative.
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Hu L, Zhang S, Xue Y, Han J, Yi H, Ke Y, Xia Y, Wang S. Rapid Identification of Pseudomonas fluorescens Harboring Thermostable Alkaline Protease by Real-Time Loop-Mediated Isothermal Amplification. J Food Prot 2022; 85:414-423. [PMID: 34855939 DOI: 10.4315/jfp-21-272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 11/29/2021] [Indexed: 11/11/2022]
Abstract
ABSTRACT Thermostable alkaline protease (TAP) harbored by Pseudomonas fluorescens decomposes protein in milk and dairy products, leading to milk and dairy product spoilage during storage. Thus, a specific, sensitive, rapid, and simple method is required to detect TAP-harboring P. fluorescens. Two sets of primers targeting the aprX and gyrB genes of P. fluorescens were designed. The detection system and conditions were optimized, and a real-time loop-mediated isothermal amplification (real-time LAMP) method was developed for the simultaneous detection of TAP-harboring P. fluorescens in two separate reaction tubes. The phylogenetic tree targeting aprX showed that P. fluorescens and Pseudomonas lurida clustered on the same branch. The phylogenetic tree targeting gyrB showed that P. fluorescens clustered on the same branch with 95% confidence value, whereas P. lurida clustered on different branches. DNA of 16 strains of P. fluorescens and 34 strains of non-P. fluorescens was detected by real-time LAMP. TAP-harboring P. fluorescens can only be identified when the real-time LAMP detection results of both aprX and gyrB are positive. The dissociation temperatures of aprX and gyrB in the real-time LAMP-amplified products were approximately 90.0 and 88.0°C, respectively. The detection limits of the real-time LAMP targeting aprX and gyrB were 4.9 CFU per reaction in pure culture and 2.2 CFU per reaction in skimmed milk. The coefficient of variation of the repeatability test was less than 2%, indicating that the established real-time LAMP of P. fluorescens targeting gyrB and aprX has good stability and repeatability. Real-time LAMP was used to test 200 raw milk samples for the presence of TAP-harboring P. fluorescens in 3 h, and the coincidence rate of the results with those obtained using the traditional method, which takes at least 5 to 7 days, was 100%. Real-time LAMP will be a practical and effective method for accurate and rapid identification of TAP-harboring P. fluorescens in raw milk. HIGHLIGHTS
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Affiliation(s)
- Lianxia Hu
- College of Chemical Engineering, Shijiazhuang University, Shijiazhuang, Hebei 050035, People's Republic of China
| | - Shufei Zhang
- College of Food Science and Biology, Hebei University of Science and Technology, Shijiazhuang, Hebei 050018, People's Republic of China
| | - Yuling Xue
- Shijiazhuang Junlebao Dairy Co., Ltd., No. 68, Shitong Road, Shijiazhuang, Hebei 050221, People's Republic of China
| | - Junhua Han
- College of Food Science and Biology, Hebei University of Science and Technology, Shijiazhuang, Hebei 050018, People's Republic of China
| | - Huaxi Yi
- College of Food Science and Engineering, Ocean University of China, Qingdao 266003, People's Republic of China
| | - Yuehua Ke
- Center for Disease Control and Prevention of PLA, No. 20, Dongdajie Street, Fengtai District, Beijing 100071, People's Republic of China
| | - Yongjun Xia
- Shanghai Engineering Research Center of Food Microbiology, School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, People's Republic of China
| | - Shijie Wang
- College of Food Science and Biology, Hebei University of Science and Technology, Shijiazhuang, Hebei 050018, People's Republic of China.,Shijiazhuang Junlebao Dairy Co., Ltd., No. 68, Shitong Road, Shijiazhuang, Hebei 050221, People's Republic of China
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Luiz LL, de Fatima Bertachi Pinto L, de Souza Correia S, Bruzaroski SR, Fagnani R, de Sousa CHB, Ludovico A, Aragon Alegro LC, Santana EHWD. High populations of psychrotrophs in milk affect the quality characteristics of Mozzarella cheese. INT J DAIRY TECHNOL 2022. [DOI: 10.1111/1471-0307.12843] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Lucas Lima Luiz
- Master Program in Science and Technology of Milk and Dairy Products Pitágoras Unopar University (UNOPAR) Av Paris, 675 Londrina 86041‐120 Brazil
| | - Leticia de Fatima Bertachi Pinto
- Master Program in Science and Technology of Milk and Dairy Products Pitágoras Unopar University (UNOPAR) Av Paris, 675 Londrina 86041‐120 Brazil
| | - Selma de Souza Correia
- Master Program in Science and Technology of Milk and Dairy Products Pitágoras Unopar University (UNOPAR) Av Paris, 675 Londrina 86041‐120 Brazil
| | - Samera Rafaela Bruzaroski
- Master Program in Science and Technology of Milk and Dairy Products Pitágoras Unopar University (UNOPAR) Av Paris, 675 Londrina 86041‐120 Brazil
| | - Rafael Fagnani
- Master Program in Science and Technology of Milk and Dairy Products Pitágoras Unopar University (UNOPAR) Av Paris, 675 Londrina 86041‐120 Brazil
| | - Cínthia Hoch Batista de Sousa
- Master Program in Science and Technology of Milk and Dairy Products Pitágoras Unopar University (UNOPAR) Av Paris, 675 Londrina 86041‐120 Brazil
| | - Agostinho Ludovico
- Master Program in Science and Technology of Milk and Dairy Products Pitágoras Unopar University (UNOPAR) Av Paris, 675 Londrina 86041‐120 Brazil
| | - Lina Casale Aragon Alegro
- Master Program in Science and Technology of Milk and Dairy Products Pitágoras Unopar University (UNOPAR) Av Paris, 675 Londrina 86041‐120 Brazil
| | - Elsa Helena Walter de Santana
- Master Program in Science and Technology of Milk and Dairy Products Pitágoras Unopar University (UNOPAR) Av Paris, 675 Londrina 86041‐120 Brazil
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Müller T, Maciel MJ, Rempel C. Qualidade físico-química e microbiológica do leite bovino do Vale do Taquari no Rio Grande do Sul, Brasil. CIÊNCIA ANIMAL BRASILEIRA 2022. [DOI: 10.1590/1809-6891v23e-72986p] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Resumo O objetivo do presente estudo foi verificar a qualidade do leite cru refrigerado das propriedades produtoras de leite e do leite cru refrigerado, pasteurizado e Ultra High Temperature (UHT) das indústrias do Vale do Taquari no Rio Grande do Sul, Brasil. Foram realizadas análises de composição do leite, análises físico-químicas e análises microbiológicas, estabelecidas pela legislação, além de coliformes totais e termotolerantes, contagem de psicrotróficos nos três tipos de leite, contagem de mesófilos no leite pasteurizado e no leite UHT das indústrias. As coletas ocorreram em duas indústrias e 33 propriedades produtoras de leite. Em relação às propriedades, duas (6%) apresentaram leite com acidez acima do estabelecido pela legislação e três (9%) apresentaram leite com contagem bacteriana total (CBT) acima do estabelecido. O leite da indústria 1 apresentou acidez, CBT e densidade fora dos padrões estabelecidos. As duas indústrias e 53,2% das propriedades apresentaram leite com contagem de células somáticas (CCS) acima do determinado pela legislação. O leite das indústrias demonstrou maiores quantidades de CCS, CBT, psicrotróficos e coliformes totais e termotolerantes que o leite das propriedades produtoras de leite e o leite da indústria 1 apresentou maiores quantidades que a indústria 2, nos parâmetros microbiológicos.
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Quintieri L, Caputo L, Brasca M, Fanelli F. Recent Advances in the Mechanisms and Regulation of QS in Dairy Spoilage by Pseudomonas spp. Foods 2021; 10:3088. [PMID: 34945641 PMCID: PMC8701193 DOI: 10.3390/foods10123088] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 11/28/2021] [Accepted: 12/08/2021] [Indexed: 11/16/2022] Open
Abstract
Food spoilage is a serious issue dramatically impacting the worldwide need to counteract food insecurity. Despite the very expensive application of low temperatures, the proper conservation of fresh dairy products is continuously threatened at different stages of production and commercialization by psychrotrophic populations mainly belonging to the Pseudomonas genus. These bacteria cause discolouration, loss of structure, and off-flavours, with fatal implications on the quality and shelf-life of products. While the effects of pseudomonad decay have been widely reported, the mechanisms responsible for the activation and regulation of spoilage pathways are still poorly explored. Recently, molecule signals and regulators involved in quorum sensing (QS), such as homoserine lactones, the luxR/luxI system, hdtS, and psoR, have been detected in spoiled products and bacterial spoiler species; this evidence suggests the role of bacterial cross talk in dairy spoilage and paves the way towards the search for novel preservation strategies based on QS inhibition. The aim of this review was to investigate the advancements achieved by the application of omic approaches in deciphering the molecular mechanisms controlled by QS systems in pseudomonads, by focusing on the regulators and metabolic pathways responsible for spoilage of fresh dairy products. In addition, due the ability of pseudomonads to quickly spread in the environment as biofilm communities, which may also include pathogenic and multidrug-resistant (MDR) species, the risk derived from the gaps in clearly defined and regulated sanitization actions is underlined.
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Affiliation(s)
- Laura Quintieri
- Institute of Sciences of Food Production, National Research Council of Italy, 70126 Bari, Italy; (L.C.); (F.F.)
| | - Leonardo Caputo
- Institute of Sciences of Food Production, National Research Council of Italy, 70126 Bari, Italy; (L.C.); (F.F.)
| | - Milena Brasca
- Institute of Sciences of Food Production, National Research Council of Italy, 20133 Milan, Italy;
| | - Francesca Fanelli
- Institute of Sciences of Food Production, National Research Council of Italy, 70126 Bari, Italy; (L.C.); (F.F.)
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Photodynamic inactivation of Pseudomonas fluorescens in Minas Frescal cheese using curcumin as a photosensitizer. Lebensm Wiss Technol 2021. [DOI: 10.1016/j.lwt.2021.112143] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Paludetti LF, O'Callaghan TF, Sheehan JJ, Gleeson D, Kelly AL. Effect of Pseudomonas fluorescens proteases on the quality of Cheddar cheese. J Dairy Sci 2020; 103:7865-7878. [PMID: 32600766 DOI: 10.3168/jds.2019-18043] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 04/10/2020] [Indexed: 12/31/2022]
Abstract
The objective of this study was to investigate the effect of adding different levels of a thermoresistant protease produced by a Pseudomonas fluorescens strain to milk on the manufacture and quality of Cheddar cheese. Fresh raw milk was collected, standardized, and pasteurized at 72°C for 15 s, and the enzyme was added to give a protease activity of 0.15 or 0.60 U/L (treatments P1 and P4, respectively), while one sample had no enzyme added (control). Milk was stored at 4°C for 48 h and Cheddar cheese was manufactured after 0 and 48 h of storage. Results indicated that the protease was active in milk during 48 h of storage; however, its effect on milk composition was minimal. The protein that was preferentially hydrolyzed by the protease over storage was β-casein, followed by κ-casein. The mean cheese yield and recovery of fat and protein obtained for all cheeses were not affected by protease activity. The protease showed low activity during cheese manufacture, possibly because of unfavorable conditions, including low pH. One of the factors that might have influenced protease activity was the pH of the curd (approximately 6.55 after acidification and 5.35 at milling), which was lower than that at which the enzyme would have optimum activity (pH 7 to 9). Consequently, the composition, pH, patterns of proteolysis, and hardness of all cheeses produced were similar and in accordance with values expected for that type of cheese, independently of the protease activity level. However, slight increases in proteolysis were observed in P4 cheeses and produced using milk stored for 48 h. Both the P1 and P4 cheeses had higher concentrations of free amino acids (FAA) compared with the control, whereas urea-PAGE electrophoretograms indicated a greater breakdown of caseins in the P4 cheese samples, which may be related to possible increases in numbers of proteolytic bacteria in milk during storage. Therefore, the thermoresistant psychrotrophic bacterial protease(s) tested in this study may affect the manufacture or quality of Cheddar cheese during ripening to a relatively limited extent. However, controlling initial levels of proteolytic bacteria in raw milk remains essential, because proteolysis affects the development of flavor and texture in cheese.
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Affiliation(s)
- Lizandra F Paludetti
- Teagasc Animal & Grassland Research and Innovation Centre, Moorepark, Fermoy, P61 C996 County Cork, Ireland; School of Food and Nutritional Sciences, University College Cork, T12 K8AF County Cork, Ireland
| | - Tom F O'Callaghan
- Teagasc Food Research Centre, Moorepark, Fermoy, P61 C996 County Cork, Ireland
| | - Jeremiah J Sheehan
- Teagasc Food Research Centre, Moorepark, Fermoy, P61 C996 County Cork, Ireland.
| | - David Gleeson
- Teagasc Animal & Grassland Research and Innovation Centre, Moorepark, Fermoy, P61 C996 County Cork, Ireland
| | - Alan L Kelly
- School of Food and Nutritional Sciences, University College Cork, T12 K8AF County Cork, Ireland
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