Dairy Spoilage Microorganisms, Mechanisms and Novel Preservation Strategies

A special issue of Foods (ISSN 2304-8158). This special issue belongs to the section "Dairy".

Deadline for manuscript submissions: closed (15 November 2021) | Viewed by 14541

Special Issue Editors

Institute of Sciences of Food Production, Italian National Council of Research, ISPA-CNR, Via Celoria 2, 20133 Milan, Italy
Interests: food microbiology; dairy science; raw milk cheese; food quality; food safety; food spoilage
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Reducing food spoilage and improving food quality are some of the biggest challenges facing food insecurity and food waste, which represent two of the most current social issues of this century.

In the dairy industry, spoilage causes losses of billions of dollars worldwide every year; in Europe, 20% of total production is lost every year. Microbial spoilage produces visible, such as discoloration, or non-visible defects, such as off-odor and -flavors, which impact the shelf life of dairy products. Proteolysis, lipolysis and pigments released by various microorganisms (gram-negative bacteria, yeasts, molds, and spore-forming bacteria) are some of the most characterized spoilage activities, although mechanisms responsible for their production and activation are still poorly explored; however, most of them are quorum sensing (QS) regulated, suggesting its potential role in dairy spoilage. Molecule signals have been detected in spoiled products where they affect microbial biodiversity and metabolic activities. Thus, preservation strategies blocking this communication system are considered as promising in counteracting spoilage phenomena.

This Special Issue aims to provide a fundamental understanding of the role of microbial cross-talk in the evolution of dairy spoilage, with respect to microbiota composition, metabolic pathways, enzymes and molecules involved in spoilage activity. Omics technologies are continuously offering new insights into the characterization of this issue. Genomics, metagenomics, proteomics and metabolomics studies will help us to understand the microbial ecology of spoiled products, and can be further addressed in this Special Issue. The development of novel preservation strategies, such as the utilization of natural antimicrobials and QS inhibitors, and their impact on the shelf life of dairy products, is welcomed. 

Dr. Francesca Fanelli
Dr. Laura Quintieri
Dr. Milena Brasca
Guest Editors

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Keywords

  • dairy microbiology
  • biodiversity of the spoilage microbiota
  • spoilage mechanisms
  • genomics
  • metagenomics
  • proteomics
  • metabolomics
  • quorum sensing
  • biofilm
  • antibiofilm agents
  • natural antimicrobials
  • preservation techniques

Published Papers (4 papers)

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Research

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13 pages, 778 KiB  
Article
Characterization of Vegetative Bacillus cereus and Bacillus subtilis Strains Isolated from Processed Cheese Products in an Italian Dairy Plant
by Angela Maria Catania, Tiziana Civera, Pierluigi Aldo Di Ciccio, Maria Ausilia Grassi, Patrizia Morra and Alessandra Dalmasso
Foods 2021, 10(11), 2876; https://0-doi-org.brum.beds.ac.uk/10.3390/foods10112876 - 21 Nov 2021
Cited by 9 | Viewed by 2297
Abstract
Processed cheese is a commercial product characterized by high microbiological stability and extended shelf life obtained through the application of severe heat treatment. However, spore-forming bacteria can survive through thermal processes. Among them, microorganisms belonging to Bacillus genus have been reported. In this [...] Read more.
Processed cheese is a commercial product characterized by high microbiological stability and extended shelf life obtained through the application of severe heat treatment. However, spore-forming bacteria can survive through thermal processes. Among them, microorganisms belonging to Bacillus genus have been reported. In this study, we examined the microbiological population of the first hours’ production of processed cheeses in an Italian dairy plant during two seasons, between June and October 2020. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to identify bacteria colonies, allowing the isolation of Bacillus cereus and Bacillussubtilis strains. These results were further confirmed by amplification and sequencing of 16 rRNA bacterial region. A multi-locus sequence type (MLST) analysis was performed to assess the genetic similarity among a selection of isolates. The fourteen B. cereus strains showed two sequence types: ST-32 was observed in only one strain and the ST-371 in the remaining thirteen isolates. On the contrary, all twenty-one B. subtlis strains, included in the study, showed a new allelic profile for the pycA gene, resulting in a new sequence type: ST-249. For B. cereus strains, analysis of toxin genes was performed. All isolates were positive for nheABC, entFM, and cytK, while hblABCD, bceT, and ces were not detected. Moreover, the biofilm-forming ability of B. cereus and B. subtilis strains was assessed, and all selected isolates proved to be biofilm formers (most of them were stronger producers). Considering the genetical similarity between isolates, jointly with the capacity to produce biofilm, the presence of a recurring Bacillus population could be hypothesized. Full article
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14 pages, 1776 KiB  
Article
Proteolytic Traits of Psychrotrophic Bacteria Potentially Causative of Sterilized Milk Instability: Genotypic, Phenotypic and Peptidomic Insight
by Stefano Morandi, Valentina Pica, Fabio Masotti, Stefano Cattaneo, Milena Brasca, Ivano De Noni and Tiziana Silvetti
Foods 2021, 10(5), 934; https://0-doi-org.brum.beds.ac.uk/10.3390/foods10050934 - 24 Apr 2021
Cited by 4 | Viewed by 2540
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, [...] Read more.
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. Full article
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8 pages, 562 KiB  
Communication
Pseudomonas spp.: Are Food Grade Organic Acids Efficient against These Spoilage Microorganisms in Fresh Cheeses?
by Erica Tirloni, Cristian Bernardi and Simone Stella
Foods 2021, 10(4), 891; https://0-doi-org.brum.beds.ac.uk/10.3390/foods10040891 - 19 Apr 2021
Cited by 3 | Viewed by 2512
Abstract
Psychrotolerant Pseudomonas spp. are among the most common spoilage agents in fresh, soft and semi-soft cheeses; therefore, hurdles inhibiting their growth are in strong demand by producers. This study aimed to establish Minimal Inhibiting Concentrations (MICs) of lactic and acetic acid towards P. [...] Read more.
Psychrotolerant Pseudomonas spp. are among the most common spoilage agents in fresh, soft and semi-soft cheeses; therefore, hurdles inhibiting their growth are in strong demand by producers. This study aimed to establish Minimal Inhibiting Concentrations (MICs) of lactic and acetic acid towards P. fluorescens and to evaluate the efficacy of a cheese surface treatment with these two organic acids. MICs were determined in Brain Heart Infusion broth at 30 °C: the inhibition was achieved at a concentration of 49.96 mM and 44.40 mM of acetic and lactic acid, respectively. Two series of inhibition tests were performed on fresh “Primo sale” cheese, inoculated with P. brenneri MGM3, then dipped into different acid solutions (acetic acid: 49.96, 99.92 and 149.88 mM; lactic acid: 44.40, 88.80 and 133.20 mM) and stored at 6 °C. P. brenneri MGM3 were enumerated, including a control series. A significantly lower growth was revealed at the highest concentrations tested, both for acetic (p < 0.01) and lactic acid (p < 0.05) if compared to control samples. A conditioning of “Primo sale” surface with organic acid solutions could be a useful hurdle for Pseudomonas inhibition and shelf-life extension; it should be applied in combination with other mild interventions to fight spoilage and maintain the original product characteristics. Full article
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Review

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27 pages, 1469 KiB  
Review
Recent Advances in the Mechanisms and Regulation of QS in Dairy Spoilage by Pseudomonas spp.
by Laura Quintieri, Leonardo Caputo, Milena Brasca and Francesca Fanelli
Foods 2021, 10(12), 3088; https://0-doi-org.brum.beds.ac.uk/10.3390/foods10123088 - 13 Dec 2021
Cited by 11 | Viewed by 4385
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 [...] Read more.
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. Full article
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