Invited review: Controlling dairy product spoilage to reduce food loss and waste

Prevention and control strategies for psychrophilic Pseudomonas fluorescens in food: A review

Psychrophilic Pseudomonas fluorescens can secrete extracellular enzymes, biofilms, and other substances even under refrigeration conditions, which have a negative impact on the quality of dairy products, aquatic products, meat products, produce, and other foods, causing food spoilage and huge economic losses. Therefore, strengthening the prevention and control of psychrophilic P. fluorescens in food is of great significance. Although some reviews have introduced information on P. fluorescens, there are few reviews that provide detailed information on the psychrophilic mechanism, detection, prevention, and control methods of psychrophilic P. fluorescens. Therefore, to comprehensively address the shortcomings of previous reviews, this review provides a detailed overview of the physiological characteristics, secreted spoilage factors, psychrophilic mechanisms, and prevention and control methods, such as bacteriophages, quorum sensing inhibitors, and nanomaterials of P. fluorescens. And future research directions for the prevention and control strategies of P. fluorescens are discussed. The future research focus will be on strengthening the detection of P. fluorescens and adopting a combination of multiple technologies to prevent and control P. fluorescens without affecting food nutrition and quality while preventing the occurrence of drug resistance. This article aims to provide references for improving the quality and safety of refrigerated food and extending its shelf life.

Raw milk at refrigeration temperature displays an independent microbiota dynamic regardless Listeria monocytogenes contamination

Dairy products made of raw milk are associated with hypervirulent L. monocytogenes clonal complexes (CCs) CC1, CC4, and CC6, and cause half of the reported listeriosis outbreaks in Europe. However, it is currently unknown whether the overrepresentation of L. monocytogenes hypervirulent clones in dairy products made of raw milk is conditioned by an alteration in the native raw milk microbiota growth and/or composition. In this study, the lag phase, maximal growth rate, and the final maximal concentration of mesophilic aerobic bacteria from native raw milk bacteria were measured at refrigerated temperature (4 °C) in the presence and absence of L. monocytogenes contamination. The raw milk microbiota composition and dynamics were evaluated in the presence and absence of L. monocytogenes hypervirulent (CC1, CC4, CC6), and hypovirulent (CC9 and CC121) clones at 4 °C by using 16S rRNA high-throughput sequencing. Our results showed that the growth and composition of the microbial communities naturally present in raw milk are independent of the contamination with hyper- or hypovirulent L. monocytogenes CCs at refrigeration temperature. Pseudomonas was the most abundant genus in raw milk on days 11 and 21, while Carnobacterium was the second most abundant genus regardless of the contaminant L. monocytogenes CCs. Altogether these results suggest that the overrepresentation of hypervirulent L. monocytogenes CC1, CC4, and CC6 in dairy products is not the consequence of a differential alteration in the native composition of the raw milk microbiota.

Diversity and spoilage potential of Pseudomonas spp. from Spanish milk and dairy products: Impact on fresh cheese and milk quality

Psychrotrophic Pseudomonas spp. contaminate milk and dairy products, producing heat-resistant enzymes and pigments that reduce their shelf life. Identifying spoiling strains is essential for tracing contamination and improving preservation. This study examines 208 Pseudomonas spp. isolates from Spanish dairy products, assessing their genetic diversity and spoilage potential in vitro and under simulated storage. Pulsed-field gel electrophoresis (PFGE) identified 108 distinct strains, clustered into 70 groups (≥ 80 % similarity), showing high diversity. Gene sequencing (ileS or rpoD) classified the strains into 20 species, with P. fluorescens (19 %), P. fragi (16 %), P. lundensis (12 %), and P. shahriarae (6 %) being predominant. P. shahriarae, P. atacamensis, P. salmasensis, P. solani, and P. canadensis were isolated from milk or dairy products for the first time. In fresh cheese, 89 % of Pseudomonas spp. caused discoloration (fluorescent yellow, creamy, orange, and blue) after 7 days of cold storage. In refrigerated milk, 48 % of strains showed significant proteolysis after 5 days, with OPA (o-Phthaldialdehyde-based method) values > 0.274, especially some P. fluorescens, P. gessardii, P. fulva, P. shahriarae, Pseudomonas spp., and P. koreensis strains. After simulated UHT treatment and accelerated storage, 75 % of strains retained thermostable proteolytic activity, especially P. fluorescens, P. proteolytica, P. shahriarae, and P. fulva strains. The aprX gene, coding for a thermostable protease, was present in 57 % of strains, suggesting other proteases may also be produced. Overall, the isolated Pseudomonas spp. led to different spoilage patterns during milk and fresh cheese storage, emphasizing the need for specific strain identification to improve preservation strategies.

High-pressure processing and heat treatment of Murrah buffalo milk: Comparative study on microbial changes during refrigerated storage

This study aims to evaluate the effect of high-pressure processing (HPP) (500 and 600 MPa for 3 min and 5 min) on the microbial changes of Murrah buffalo milk in comparison to heat treatment (72 °C for 15 s of holding time) during refrigerated storage of 28 days. The results indicated that the total plate count (TPC) of raw milk at day 0 was 5.5 ± 0.6 log10 CFU/mL. At day 0, heat treatment lowered TPC to 3.9 ± 0.6, while HPP treatment was in the range of 4.1 ± 0.3 to 4.8 ± 0.6 log10 CFU/mL. Similarly, lowered yeast and mold count and lactic acid bacteria were noted in heat- and HPP-treated milk samples compared to the control sample during refrigerated storage. There were no Staphylococcus aureus and Escherichia coli detected in heat and HPP-treated samples. Heat or HPP treatment at 600 MPa for 5 min significantly extended the shelf-life of Murrah buffalo milk for three weeks at the refrigerated storage. In addition, HPP treatment did not alter the pH, lightness (L* value), protein, or fat content of Murrah buffalo milk during refrigerated storage. Hence HPP at 600 MPa for 5 min could be a suitable alternative to conventional heat treatment.

Comparison of chemical constituents in Lysimachia species and their antimicrobial activity for extending the shelf life of foods

Food spoilage causes significant economic losses and endangers human health. Developing novel antimicrobial agents and preservatives is urgently needed for anti-foodborne diseases and improving food storage. Zhen Zhu Cai (Lysimachia) species are well-known edible plants among the East Asian populace that clear heat and anti-aging. Here, 70 fractions of ten Lysimachia species were compared, among which the bioactive fraction (KBZZC-05) was characterized and isolated to evaluate its antimicrobial activity, and compounds 21 and 23 were obtained under bioactive guidance. The KBZZC-05, 21, and 23 inhibited both spoilage organisms and foodborne pathogens (MICs = 2-256 μg/mL) better than potassium sorbate (MIC >256 μg/mL). It removed biofilms, causing surface morphology changes in bacteria. Additionally, KBZZC-05 (128 μg/mL) extended food shelf life through its antioxidant (P < 0.01 vs CK) and resistance to spoilage microorganisms. This study indicates that bioactive KBZZC-05 is a potentially non-toxic and eco-friendly botanical microbicide and preservative that can be used to treat foodborne diseases and for food storage.

Ultrasonic processing: effects on the physicochemical and microbiological aspects of dairy products

Dairy products that are contaminated by pathogenic microorganisms through unhygienic farm practices, improper transportation, and inadequate quality control can cause foodborne illness. Furthermore, inadequate storage conditions can increase the microflora of natural spoilage, leading to rapid deterioration. Ultrasound processing is a popular technology used to improve the quality of milk products using high-frequency sound waves. It can improve food safety and shelf life by modifying milk protein and fats without negatively affecting nutritional profile and sensory properties, such as taste, texture, and flavor. Ultrasound processing is effective in eliminating pathogenic microorganisms, such as Salmonella, Escherichia coli, Staphylococcus aureus, and Listeria monocytogenes. However, the efficiency of processing is determined by the type of microorganism, pH, and temperature of the milk product, the frequency and intensity of the applied waves, as well as the sonication time. Ultrasound processing has been established to be a safe and environmentally friendly alternative to conventional heat-based processing technologies that lead to the degradation of milk quality. There are some disadvantages to using ultrasound processing, such as the initial high cost of setting it up, the production of free radicals, the deterioration of sensory properties, and the development of off-flavors with lengthened processing times. The aim of this review is to summarize current research in the field of ultrasound processing and discuss future directions.

Disinfection in a salmon processing plant: Impact on bacterial communities and efficacy towards foodborne bacteria and biofilms

Salmon aquaculture is the fastest growing food production system in the world. Deficiencies in the quality or safety of salmon can have global repercussions. Controlling food safety aspects during production is therefore essential. Here, we investigate the state of hygiene in a salmon processing plant using next generation sequencing and classical culture-dependent methods to characterize the surface microbiota before and after cleaning and disinfection (C&D) at ten surface sampling points. Total aerobic counts revealed an average reduction in the bacterial loads of 1.1 log CFU/cm2 by C&D. The highest relative abundance in the core microbiota before C&D was assigned to Acinetobacter, Mycoplasmataceae, Pseudomonas and Enterobacteriaceae in descending order. After C&D, we observed a significant increase in the relative abundance of Pseudomonas (p < 0.05). However, variations were found between conveyors, processing machines and drains. To assess the efficacy of commercial disinfectants, we performed susceptibility assays using advanced robotic high-throughput technologies and included foodborne bacteria which may affect food safety and spoilage. These included 128 Pseudomonas isolates, 46 Aeromonas isolates and 59 Enterobacterales isolates sampled from the salmon processing plant. Generally, minimum inhibitory concentrations (MICs) of the disinfectants were below the user concentration recommended by the producer for most isolates. BacTiter-Glo biofilm assays revealed that 30 min exposure to six out of eight commercial disinfectants resulted in an average reduction of relative luminescence >95 % in 59 single-species biofilms selected for screening. However, disinfection alone may not always be sufficient to eradicate biofilms completely. C&D routines must therefore be continuously assessed to maintain food safety and quality. The results from this study can contribute to understand and improve the state of hygiene in salmon processing environments.

Spoilage microbial groups in dairy industry

Milk and dairy products can be spoiled by microorganisms from the raw milk microbiota as well as resident microorganisms in dairy industries, with some being related to more than one type of spoilage due to their metabolic versatility. Different types of spoilage have harmed dairy production, including milk destabilization by enzymatic activity, cheese blowing, discolorations, acidification, off-flavors production, slime formation, and ropiness. Generally, the compounds most associated with these problems are enzymes, secondary metabolites, biogenic amines, lactic acid, volatile compounds, polysaccharides, among others. Additionally, many microorganisms that are beneficial in some dairy products also have the potential to cause spoilage. Here, the main groups of microorganisms associated with the spoilage of milk and dairy products are described, and measures for their control and prevention are presented.

Recent Development in Detection and Control of Psychrotrophic Bacteria in Dairy Production: Ensuring Milk Quality

Milk is an ideal environment for the growth of microorganisms, especially psychrotrophic bacteria, which can survive under cold conditions and produce heat-resistant enzymes. Psychrotrophic bacteria create the great problem of spoiling milk quality and safety. Several ways that milk might get contaminated by psychrotrophic bacteria include animal health, cowshed hygiene, water quality, feeding strategy, as well as milk collection, processing, etc. Maintaining the quality of raw milk is critically essential in dairy processing, and the dairy sector is still affected by the premature milk deterioration of market-processed products. This review focused on the recent detection and control strategies of psychrotrophic bacteria and emphasizes the significance of advanced sensing methods for early detection. It highlights the ongoing challenges in the dairy industry caused by these microorganisms and discusses future perspectives in enhancing milk quality through innovative rapid detection methods and stringent processing controls. This review advocates for a shift towards more sophisticated on-farm detection technologies and improved control practices to prevent spoilage and economic losses in the dairy sector.

Microbial food spoilage: impact, causative agents and control strategies

Microbial food spoilage is a major contributor to food waste and, hence, to the negative environmental sustainability impacts of food production and processing. Globally, it is estimated that 15-20% of food is wasted, with waste, by definition, occurring after primary production and harvesting (for example, in households and food service establishments). Although the causative agents of food spoilage are diverse, many microorganisms are major contributors across different types of foods. For example, the genus Pseudomonas causes spoilage in various raw and ready-to-eat foods. Aerobic sporeformers (for example, members of the genera Bacillus, Paenibacillus and Alicyclobacillus) cause spoilage across various foods and beverages, whereas anaerobic sporeformers (for example, Clostridiales) cause spoilage in a range of products that present low-oxygen environments. Fungi are also important spoilage microorganisms, including in products that are not susceptible to bacterial spoilage due to their low water activity or low pH. Strategies that can reduce spoilage include improved control of spoilage microorganisms in raw material and environmental sources as well as application of microbicidal or microbiostatic strategies (for example, to products and packaging). Emerging tools (for example, systems models and improved genomic tools) represent an opportunity for rational design of systems, processes and products that minimize microbial food spoilage.

Microbiome mapping in dairy industry reveals new species and genes for probiotic and bioprotective activities

The resident microbiome in food industries may impact on food quality and safety. In particular, microbes residing on surfaces in dairy industries may actively participate in cheese fermentation and ripening and contribute to the typical flavor and texture. In this work, we carried out an extensive microbiome mapping in 73 cheese-making industries producing different types of cheeses (fresh, medium and long ripened) and located in 4 European countries. We sequenced and analyzed metagenomes from cheese samples, raw materials and environmental swabs collected from both food contact and non-food contact surfaces, as well as operators' hands and aprons. Dairy plants were shown to harbor a very complex microbiome, characterized by high prevalence of genes potentially involved in flavor development, probiotic activities, and resistance to gastro-intestinal transit, suggesting that these microbes may potentially be transferred to the human gut microbiome. More than 6100 high-quality Metagenome Assembled Genomes (MAGs) were reconstructed, including MAGs from several Lactic Acid Bacteria species and putative new species. Although microbial pathogens were not prevalent, we found several MAGs harboring genes related to antibiotic resistance, highlighting that dairy industry surfaces represent a potential hotspot for antimicrobial resistance (AR) spreading along the food chain. Finally, we identified facility-specific strains that can represent clear microbial signatures of different cheesemaking facilities, suggesting an interesting potential of microbiome tracking for the traceability of cheese origin.

Identification and Characterization of Microorganisms Isolated from Non-compliant and/or Atypical Dairy Products in Canada

Despite good manufacturing practices and rigorous cleaning and sanitizing procedures established in dairy processing plants, microbiological contamination remains the main cause of products being non-compliant and/or atypical and hence not fit for human consumption. The objective of this study was to isolate, identify and characterize bacteria, yeasts and molds associated with substandard dairy products in Canada and to create a collection of reference isolates. In addition to conventional microbiological characterization, each isolate was tested for biofilm-forming ability and susceptibility to heat, antimicrobial agents, and common industrial disinfectants. Among the 105 microbial strains isolated from pasteurized milk, cream, and cheese samples, 24 bacterial isolates, belonging mainly to the genus Pseudomonas, were shown to be moderate or strong biofilm producers in 96-well plates and highly resistant to peracetic acid (100 ppm, 5 min contact time) and sodium hypochlorite (70 ppm, 5 min contact time). In addition, 56 bacterial isolates, including Acinetobacter baumannii, Enterobacter bugandensis, Klebsiella pneumoniae and Pseudomonas spp., were found resistant to ampicillin, fosfomycin and/or ceftriaxone, while 14 others, such as Bacillus spp. and Macrococcus spp., withstood a heat treatment equivalent to low-temperature long-time pasteurization (63°C for 30 min). This descriptive study provides new information on potential problematic microorganisms in dairies and will guide the development of novel control strategies intended to prevent and reduce microbiological contamination and the associated economic losses.

Invited review: Role of Bacillus licheniformis in the dairy industry- friends or foes?

Bacillus licheniformis is one of the major spore-forming bacteria with great genotypic diversity in raw milk, dairy ingredients, final dairy products, and is found throughout the dairy processing continuum. Though being widely used as a probiotic strain, this species also serves as a potential risk in the dairy industry based on its roles in foodborne illness and dairy spoilage. Biofilm formation of B. licheniformis in combined with the heat resistance of its spores, make it impossible to prevent the presence of B. licheniformis in final dairy products by traditional cleaning and disinfection procedures. Despite the extensive efforts on the identification of B. licheniformis from various dairy samples, no reviews have been reported on both hazard and benefits of this spore-former. This review discusses the prevalence of B. licheniformis from raw milk to commercial dairy products, biofilm formation and spoilage potential of B. licheniformis, and its potential prevention methods. In addition, the potential benefits of B. licheniformis in the dairy industry were also summarized.

Sponge-like porous polyvinyl alcohol/chitosan-based hydrogel with integrated cushioning, pH-indicating and antibacterial functions

Developing a packaging material with integrated cushioning, intelligent and active functions is highly desired but remains challenging in the food industry. Here we show that a sponge-like porous hydrogel with pH-indicating and antibacterial additives can meet this requirement. We use polyvinyl alcohol and chitosan as the primary polymers to construct a hydrogel with hierarchical structures through a freeze-casting method in combination with salting-out treatment. The synergy of aggregated polymer chains and the sponge-like porous structure makes the hydrogel resilient and efficient in energy absorption. It also enables rapid movement of molecules/particles and fast reaction due to the large specific surface area of the pore structures and the large amount of free water in it, leading to a sensitive pH-indicating function. The hydrogel shows an obvious color variation within a wide pH range in 3 min. The silver nanoparticles are fixed in the dense polymer networks, enabling a lasting release of silver ions. The porous structure makes the silver ion reach the protected item in a short time, achieving an antibacterial effect against S. aureus and E. coli with little cytotoxicity. This work paves the way for fabricating multifunctional hydrogels for diverse advanced packaging systems.

Characterisation of the surface growth of Mucor circinelloides in cheese agar media using predictive mathematical models

The main objective of this work was to characterise the mycelial growth of Mucor circinelloides, one of the fungal contaminants that appear frequently in the artisan cheese production environment. The study uses primary Baranyi and Huang models to compare their parameters and predict M. circinelloides on cheese-based medium (CBA) under diverse environmental conditions (temperature range from 6 to 37 °C and 0 and 1 % NaCl concentration). However, the Baranyi model consistently estimated longer lag phases and higher surface growth rates (sgr) than the Huang model; both models showed adequate best-fit performance (exactly with the mean coefficient of determination R2 = (0.993 ± 0.020 × 10-1). The groups of primary growth parameters were analysed against temperature using the cardinal model (CM) with the following main outputs. The optimal surface growth rates (sgropt) on CBA were 6.8 and 6.5 mm/d calculated with the Baranyi and Huang models, respectively. They were reduced by approximately 46 % on the surface of the agar medium when 1 % NaCl was added. Topt was estimated in a very narrow range of 32.1-32.5 °C from both primary sgr data sets (0 % and 1 % NaCl). Similarly, Tmax values of 37.2 °C and 37.3 °C were estimated for the Baranyi and Huang models, respectively; however, they decreased at 2 °C in CBA with 1 % NaCl (Tmax = 35.1 °C). The application of CM for sgr provided an estimation of the parameter Tmin with negative values that are considered only as a theoretical output. The results provide insight into the modelling and prediction of fungi growth as a function of time and salt concentration, including the times to detect visible mycelial growth of Mucor circinelloides. The mere quantification of this phenomenon can be useful for practice. Adjusting the frequency of the cheese surface washing step with a salt solution at the early stage of ripening properly can prevent the growth of not only fast fungal growers.

A ratiometric fluorescence platform for on-site screening meat freshness

Meat freshness is related to food safety and human health. Developing a simple and effective method for on-site detection of meat freshness is essential to ensure food safety. This study aimed to explore a ratiometric fluorescence platform for on-site screening of meat freshness. We synthesized a series of benzothiazole-based fluorescent compounds (BM, BHM and BTH), each with different recognition groups for detecting meat freshness biomarkers cadaverine (Cad) and putrescine (Pte). The optimized 2-(2'-hydroxyphenyl-3-aldehyde-5-1,3-indanedione) benzothiazole (BTH) demonstrated a noticeable color and fluorescence change, a fast response (<15 min), and high selectivity and sensitivity (LOD = 70 nM) to Cad. Portable test strips based on BTH were prepared for rapid visual detection of meat freshness, which exhibited visible color and fluorescen color changes to Cad and Pte. Furthermore, a portable smartphone-based fluorescence device integrated with a self-programmed Python program was fabricated and used on-site to monitor Cad and Pte within 5 min. The BTH-loaded portable test strips were successfully employed as low-cost, high-contrast, fast-response, and smartphone-adaptable fluorescent labels for detecting Cad and Pte in meat samples under different temperatures (25 °C, 4 °C, and -20 °C). This enabled consumers and food supply chain stakeholders to quickly and visually monitor the meat freshness in real beef, chicken, and pork products.

Mild Heat Treatment and Biopreservatives for Artisanal Raw Milk Cheeses: Reducing Microbial Spoilage and Extending Shelf-Life through Thermisation, Plant Extracts and Lactic Acid Bacteria

The microbial quality of raw milk artisanal cheeses is not always guaranteed due to the possible presence of pathogens in raw milk that can survive during manufacture and maturation. In this work, an overview of the existing information concerning lactic acid bacteria and plant extracts as antimicrobial agents is provided, as well as thermisation as a strategy to avoid pasteurisation and its negative impact on the sensory characteristics of artisanal cheeses. The mechanisms of antimicrobial action, advantages, limitations and, when applicable, relevant commercial applications are discussed. Plant extracts and lactic acid bacteria appear to be effective approaches to reduce microbial contamination in artisanal raw milk cheeses as a result of their constituents (for example, phenolic compounds in plant extracts), production of antimicrobial substances (such as organic acids and bacteriocins, in the case of lactic acid bacteria), or other mechanisms and their combinations. Thermisation was also confirmed as an effective heat inactivation strategy, causing the impairment of cellular structures and functions. This review also provides insight into the potential constraints of each of the approaches, hence pointing towards the direction of future research.

Dilution Reduces Sample Matrix Effects for Rapid, Direct, and Miniaturised Phenotypic Antibiotic Susceptibility Tests for Bovine Mastitis

The time-consuming nature of current methods for detecting antimicrobial resistance (AMR) to guide mastitis treatment and for surveillance, drives innovation towards faster, easier, and more portable technology. Rapid on-farm testing could guide antibiotic selection, reducing misuse that contributes to resistance. We identify challenges that arise when developing miniaturized antibiotic susceptibility tests (AST) for rapid on-farm use directly in milk. We experimentally studied three factors: sample matrix (specifically milk or spoiled milk); the commensal bacteria found in fresh bovine milk; and result time on the performance of miniaturised AST. Microfluidic "dip-and-test" devices made from microcapillary film (MCF) were able to monitor Gram-negative bacterial growth colourimetrically even in the presence of milk and yoghurt (used to simulate spoiled milk samples), as long as this sample matrix was diluted 1:5 or more in growth medium. Growth detection kinetics using resazurin was not changed by milk at final concentrations of 20% or lower, but a significant delay was seen with yoghurt above 10%. The minimum inhibitory concentration (MIC) for ciprofloxacin and gentamicin was increased in the presence of higher concentrations of milk and yoghurt. When diluted to 1% all observed MIC were within range, indicating dilution may be sufficient to avoid milk matrix interfering with microfluidic AST. We found a median commensal cell count of 6 × 105 CFU/mL across 40 healthy milk samples and tested if these bacteria could alter microfluidic AST. We found that false susceptibility may be observed at early endpoint times if testing some pathogen and commensal mixtures. However, such errors are only expected to occur when a susceptible commensal organism is present at higher cell density relative to the resistant pathogen, and this can be avoided by reading at later endpoints, leading to a trade-off between accuracy and time-to-result. We conclude that with further optimisation, and additional studies of Gram-positive organisms, it should be possible to obtain rapid results for microfluidic AST, but a trade-off is needed between time-to-result, sample dilution, and accuracy.

Characteristics of Unripened Cow Milk Curd Cheese Enriched with Raspberry (Rubus idaeus), Blueberry (Vaccinium myrtillus) and Elderberry (Sambucus nigra) Industry By-Products

The aim of this study was to apply raspberry (Ras), blueberry (Blu) and elderberry (Eld) industry by-products (BIB) for unripened cow milk curd cheese (U-CC) enrichment. Firstly, antimicrobial properties of the BIBs were tested, and the effects of the immobilization in agar technology on BIB properties were evaluated. Further, non-immobilized (NI) and agar-immobilized (AI) BIBs were applied for U-CC enrichment, and their influence on U-CC parameters were analyzed. It was established that the tested BIBs possess desirable antimicrobial (raspberry BIB inhibited 7 out of 10 tested pathogens) and antioxidant activities (the highest total phenolic compounds (TPC) content was displayed by NI elderberry BIB 143.6 mg GAE/100 g). The addition of BIBs to U-CC increased TPC content and DPPH- (2,2-diphenyl-1-picrylhydrazyl)-radical scavenging activity of the U-CC (the highest TPC content was found in C-RaNI 184.5 mg/100 g, and strong positive correlation between TPC and DPPH- of the U-CC was found, r = 0.658). The predominant fatty acid group in U-CC was saturated fatty acids (SFA); however, the lowest content of SFA was unfolded in C-EldAI samples (in comparison with C, on average, by 1.6 times lower). The highest biogenic amine content was attained in C-EldAI (104.1 mg/kg). In total, 43 volatile compounds (VC) were identified in U-CC, and, in all cases, a broader spectrum of VCs was observed in U-CC enriched with BIBs. After 10 days of storage, the highest enterobacteria number was in C-BluNI (1.88 log10 CFU/g). All U-CC showed similar overall acceptability (on average, 8.34 points); however, the highest intensity of the emotion "happy" was expressed by testing C-EldNI. Finally, the BIBs are prospective ingredients for U-CC enrichment in a sustainable manner and improved nutritional traits.

Shotgun proteomics for the identification of yeasts responsible for pink/red discoloration in commercial dairy products

Pink/red discoloration encompasses a series of relatively common spoilage defects of commercial dairy products. In this study, we used shotgun proteomics to identify the microorganism responsible for the production of intensely red-coloured slimes found on the surface of freshly opened commercial spreadable cheese and yogurt samples. Proteome-wide characterization of microbial proteins allowed to identify 1042 and 687 gene products from Rhodotorula spp. in spreadable cheese and yogurt samples, respectively, while no significant protein scores from other microorganisms were recorded. Subsequent microbiological analyses and sequencing of the 26S rRNA gene region supported the proteomic results demonstrating that the microorganism involved was Rhodotorula mucilaginosa, a carotenoid - producing basidiomycetous that can be potentially pathogenic to humans, especially for immunocompromised individuals. This is the first time that shotgun proteomics has been used to identify a microorganism responsible for spoilage in dairy products, proposing it as a relatively fast, sensitive, and reliable alternative or complement to conventional methods for microbial identification.

Biocompatible green technology principles for the fabrication of food packaging material with noteworthy mechanical and antimicrobial properties A sustainable developmental goal towards the effective, safe food preservation strategy

Biocompatible, eco-friendly, highly economical packaging methods should be needed as conventional packaging is known to cause undesirable effects. As food packaging is the major determining factor of food safety, the selection or methods of packaging materials plays a pioneering role. With this scope, modern food technology seeks unique sustainable approaches for the fabrication of package materials with notable desired properties. The principles, features, and fabrication methodology of modern food packaging are briefly covered in this review. We extensively revealed improved packaging (nanocoating, nanolaminates, and nano clay), active packaging (antimicrobial, oxygen scavenging, and UV barrier packaging), and intelligent/smart packaging (O2 indicator, CO2 indicator, Time Temperature Indicator, freshness indicator, and pH indicator). In particular, we described the role of nanomaterials in the fabrication of packaging material. Methods for the evaluation of mechanical, barrier properties, and anti-microbial assays have been featured. The present studies suggest the possible utilization of materials in the fabrication of food packaging for the production, utilization, and distribution of safe foods without affecting nutritional values.

Economic and environmental analysis of processing plant interventions to reduce fluid milk waste

With the increased awareness about the economic and environmental impact of food waste, many interventions along food supply chains have been proposed to mitigate food waste. Even though interventions used to target food waste usually revolve around logistics and operations management, we highlight a unique solution to address this issue, specifically for fluid milk. We target the intrinsic quality of fluid milk by evaluating interventions that will extend the product shelf life. We used data from a previous fluid milk spoilage simulation model, collected price and product information from retail stores, conducted an expert elicitation, and used hedonic price regressions to determine the private and social gains to the dairy processing plant when implementing 5 different interventions to extend shelf life. Our data suggest that the value of each additional day of shelf life is approximately $0.03 and indicate that increasing periodic equipment cleaning is the most cost-effective strategy for processing plants to achieve fluid milk shelf-life improvements, both from a firm's economic standpoint and from an environmental standpoint. Importantly, the approaches reported here will be valuable to help individual firms to generate customized facility and firm specific assessments that identify the most appropriate strategies for extending the shelf life of different dairy products.

Proteolytic activity and heat resistance of the protease AprX from Pseudomonas in relation to genotypic characteristics

AprX is an alkaline metalloprotease produced by Pseudomonas spp. and encoded by its initial gene of the aprX-lipA operon. The intrinsic diversity among Pseudomonas spp. regarding their proteolytic activity is the main challenge for the development of accurate methods for spoilage prediction of ultra-high temperature (UHT) treated milk in the dairy industry. In the present study, 56 Pseudomonas strains were characterized by assessing their proteolytic activity in milk before and after lab-scale UHT treatment. From these, 24 strains were selected based on their proteolytic activity for whole genome sequencing (WGS) to identify common genotypic characteristics that correlated with the observed variations in proteolytic activity. Four groups (A1, A2, B and N) were determined based on operon aprX-lipA sequence similarities. These alignment groups were observed to significantly influence the proteolytic activity of the strains, with an average proteolytic activity of A1 > A2 > B > N. The lab-scale UHT treatment did not significantly influence their proteolytic activity, indicating a high thermal stability of proteases among strains. Amino acid sequence variation of biologically-relevant motifs in the AprX sequence, namely the Zn²⁺-binding motif at the catalytic domain and the C-terminal type I secretion signaling mechanism, were found to be highly conserved within alignment groups. These motifs could serve as future potential genetic biomarkers for determination of alignment groups and thereby strain spoilage potential.

Naturally forming benzoic acid orientates perilipin to facilitate glyceride-type polyunsaturated fatty acid degradation via fermentation behavior

Naturally forming benzoic acid in fermented dairy products accumulates in organisms and biomagnifies through collateral transport. The association between benzoic acid agglomeration and susceptible lipid nutrients remains obscure. Horizontal analysis of lipidomic alteration in response to benzoic acid was conducted and the spatially proteomic map was constructed using label-free quantitative proteomics. From synergistic integration of multi-omics in benzoic acid accumulated fermented goat milk model, the biological processes of significant proteins mostly focused on glyceride-type polyunsaturated fatty acids degradation (143.818 ± 0.51 mg/kg to 104.613 ± 0.29 mg/kg). As a physiological barrier shield, perilipin, which is coated on the surface of lipid droplets, protects triacylglycerols from cytosolic lipases, thus preventing triglyceride hydrolysis. The expression of perilipin decreased by 90% compared with the control group, leading to the decrease of triglycerides. Benzoic acid suppressed phosphatidylethanolamines and phosphatidylcholines synthesis by attenuating choline phosphotransferase and ethanolamine phosphotransferase. Less diglyceride generated by the dephosphorylation of phosphatidic acid entered choline phosphotransferase and ethanolamine phosphotransferase-mediated glycerophospholipid metabolisms. Fermentation of goat milk at a low temperature and less incubation time leads to the production of less benzoic acid and mitigation of lipid nutrient loss. The present study delineated the molecular landscape of fermented goat milk containing endogenous benzoic acid and further dissected the trajectory guiding lipid alteration to advance control of benzoic acid residue.

Invited review: Redefining raw milk quality-Evaluation of raw milk microbiological parameters to ensure high-quality processed dairy products

Raw milk typically has little bacterial contamination as it leaves the udder of the animal; however, through a variety of pathways, it can become contaminated with bacteria originating from environmental sources, the cow herself, and contact with contaminated equipment. Although the types of bacteria found in raw milk are very diverse, select groups are particularly important from the perspective of finished product quality. In particular, psychrophilic and psychrotolerant bacteria that grow quickly at low temperatures (e.g., species in the genus Pseudomonas and the family Enterobacteriaceae) and produce heat-stable enzymes, and sporeforming bacteria that survive processing hurdles in spore form, are the 2 primary groups of bacteria related to effects on processed dairy products. Understanding factors leading to the presence of these important bacterial groups in raw milk is key to reducing their influence on processed dairy product quality. Here we examine the raw milk microbiological parameters used in the contemporary dairy industry for their utility in identifying raw milk supplies that will perform well in processed dairy products. We further recommend the use of a single microbiological indicator of raw milk quality, namely the total bacteria count, and call for the development of a whole-farm approach to raw milk quality that will use data-driven, risk-based tools integrated across the continuum from production to processing and shelf-life to ensure continuous improvement in dairy product quality.

Pasteurized milk quality in Brazil: a cross-sectional study over five years

This research communication delineates the quality of pasteurized cow milk sold in Brazil from 2015 to 2020. A cross-sectional study was performed gathering 1749 samples, which were evaluated for microbiological and physicochemical parameters, including Salmonella spp., total and thermotolerant coliforms, freezing point, alkaline phosphatase and lactoperoxidase. The proportion of compliant and non-compliant samples was compared through the years and jurisdiction of the inspection services. Interactions between the design and response variables were assessed by log-linear analysis. Overall, a considerable non-conformity rate (12%) was found for at least one microbiological or physicochemical parameter. Post-pasteurization contamination by coliforms was the major challenge for dairy industries. Notably, the non-compliance rate for freezing point increased during the SARS-CoV-2 pandemic. In addition, the ability to comply was linked to the type of inspection service. Thus, it is suggested that the SARS-CoV-2 pandemic is affecting the dairy industries in Brazil, and we strengthen the need for more studies monitoring the quality of milk over the years, which could assist industries and regulatory agencies to ensure the compliance of pasteurized milk.

Extending the Shelf Life of Raw Milk and Pasteurized Milk with Plantaricin FB-2

Raw milk and pasteurized milk are characterized by a short shelf life, and drinking expired raw milk and pasteurized milk causes illness. In the study, Plantaricin FB-2 (extracted from Lactiplantibacillus plantarum FB-2) was added to liquid milk. By evaluating the microbial growth, acidity changes, protein content, and sensory changes in raw milk and pasteurized milk during storage, it was found that when Plantaricin FB-2 was added at 0.4 g/kg, the shelf life of raw milk was extended by 3 days (7 days if not added). The shelf life of pasteurized milk with Plantaricin FB-2 was extended to 31 days (25 days in the control group), and the optimal amount was 0.3 g/kg. This confirmed that Plantaricin FB-2 can effectively prolong the shelf life of raw and pasteurized milk. This study provides valuable information for the application of bacteriocins produced by Lactiplantibacillus plantarum in raw milk and pasteurized milk to improve their shelf life.

Innovative processes in smart packaging. A systematic review

Smart packaging provides one possible solution that could reduce greenhouse gas emissions. In comparison with traditional packaging, which aims to extend the product's useful life and to facilitate transport and marketing, smart packaging allows increased efficiency, for example by ensuring authenticity and traceability from the product's origin, preventing fraud and theft, and improving security. Consequently, it may help to reduce pollution, food losses, and waste associated with the food supply chain. However, some questions must be answered to fully understand the advantages and limitations of its use. What are the most suitable smart packaging technologies for use in agro-industrial subsectors such as meat, dairy, fruits, and vegetables, bakery, and pastry? What are the opportunities from a perspective of life extension, process optimization, traceability, product quality, and safety? What are the future challenges? An up-to-date, systematic review was conducted of literature relevant to the application of indicator technologies, sensors, and data carriers in smart packaging, to answer these questions. © 2022 Society of Chemical Industry.

Correlation Analysis of Microbial Contamination and Alkaline Phosphatase Activity in Raw Milk and Dairy Products

Microbial contamination in raw milk and dairy products can detrimentally affect product quality and human health. In this study, the aerobic plate count, aerobic Bacillus abundance, thermophilic aerobic Bacillus abundance, and alkaline phosphatase activity were determined in 435 raw milk, 451 pasteurized milk, and 617 sterilized milk samples collected from 13 Chinese provinces (or municipalities). Approximately 9.89% and 2.22% of raw milk and pasteurized milk samples exceeded the threshold values for the aerobic plate count, respectively. The proportions of aerobic Bacillus in raw milk, pasteurized milk, and sterilized milk were 54.02%, 14.41%, and 1.30%, respectively. The proportions of thermophilic aerobic Bacillus species were 7.36% in raw milk and 4.88% in pasteurized milk samples, and no bacteria were counted in sterilized milk. Approximately 36.18% of raw milk samples contained >500,000 mU/L of alkaline phosphatase activity, while 9.71% of pasteurized milk samples contained >350 mU/L. For raw milk, there was a positive correlation between the aerobic plate count, the aerobic Bacillus abundance, and the alkaline phosphatase activity, and there was a positive correlation between the aerobic Bacillus abundance, the thermophilic aerobic Bacillus count, and the alkaline phosphatase activity. For pasteurized milk, there was a positive correlation between the aerobic plate count, the aerobic Bacillus abundance, and the thermophilic aerobic Bacillus count; however, the alkaline phosphatase activity had a negative correlation with the aerobic plate count, the aerobic Bacillus abundance, and the thermophilic aerobic Bacillus abundance. These results facilitate the awareness of public health safety issues and the involvement of dairy product regulatory agencies in China.

Peptidomic Fingerprints of Stored UHT Milk Inoculated with Protease Extracts from Different Pseudomonas Strains Relative to aprX Expression and Visible Spoilage

Lately, concern about the protease AprX produced by Pseudomonas has increased in the dairy industry due to its ability to survive UHT treatment and spoil UHT milk. Efficient prediction methods for UHT milk spoilage are currently lacking, mainly due to high diversity in proteolytic potential between Pseudomonas strains. The present study aimed to gain more insight into the variability between Pseudomonas strains regarding proteolytic potential by comparing their proteolytic capability with their aprX expression levels and differences in peptide formation. The variability in aprX expression levels in four Pseudomonas strains were related to physical stability, milk proteolysis and peptidomic cleavage patterns of milk proteins in a storage experiment of UHT milk inoculated with protease extracellular extracts and stored for 45 days at 20 °C. A positive relationship was observed between the relative expression of aprX and milk proteolysis during storage, with the strain Pseudomonas panacis DSM 18529 showing the highest level in both parameters. This strain was the only strain to show visual gelation, which occurred after 21 days. The peptide formation analysis showed a similar protein hydrolysis pattern between strains and high hydrolysis of αs1-caseins during long-term spoilage putatively due to the activity of AprX was observed.

Graduate Student Literature Review: Farm management practices: Potential microbial sources that determine the microbiota of raw bovine milk

Environmental and herd-associated factors such as geographical location, climatic conditions, forage types, bedding, soil, animal genetics, herd size, housing, lactation stage, and udder health are exploited by farmers to dictate specific management strategies that ensure dairy operation profitability and enhance the sustainability of milk production. Along with milking routines, milking systems, and storage conditions, these farming practices greatly influence the microbiota of raw milk, as evidenced by several recent studies. During the past few years, the increased interest in high-throughput sequencing technologies combined with culture-dependent methods to investigate dairy microbial ecology has improved our understanding of raw milk community dynamics throughout storage and processing. However, knowledge is still lacking on the niche-specific communities in the farm environment, and on the factors that determine bacteria transfer to the raw milk. This review summarizes findings from the past 2 decades regarding the effects of farm management practices on the diversity of bacterial species that determine the microbiological quality of raw cow milk.

Fly-antennae-inspired biomass-based fluorescent platform for NH3 quantitative detection and visual real-time monitoring of seafood spoilage

Traditional strategies for quantitative detection of NH₃ and monitoring of seafood spoilage still have some pervasive issues of cumbersome operation, time-consuming, high-cost, and inefficient real-time monitoring, and visualization. Integration of biomass-based materials and aggregation-induced emission (AIE) fluorescence probes exhibit conceivable potential in seafood detection and environmental monitoring. Herein, a fly-antennae-inspired biomass-based solid-state fluorescent platform (PAA-FP) with effective, easy-to-use, reusable, low-cost and highly sensitive characteristics is nanoengineered for NH₃ quantitative detection (detection limit = 0.5 ppm) and visual real-time monitoring of seafood spoilage using smartphones. The PAA-FP possesses an anticipative "fly-antennae-like" microstructure and offers selective recognition of NH₃ by naked eyes in daylight with excellent solid-state fluorescence properties. Moreover, PAA-FP is simply reused at least 5 times after AcOH fumigation. Comprehensive application experiments substantiate that PAA-FP successfully achieves quantitative detection of NH₃ and realizes the visual real-time daylight monitoring of food spoilage using a simple color recognizing smartphone software. The present study demonstrates an effective fabrication strategy to explore various multifunctional biomass-based materials for sensing hazardous and noxious substances.

Easy-to-Use Visual Sensing System for Milk Freshness, Sensitized with Acidity-Responsive N-Doped Carbon Quantum Dots

This study established a flexible and eye-readable sensing system for the easy-to-use, visual detection of milk freshness, using acidity-responsive N-doped carbon quantum dots (N-CQDs). N-CQDs, rich in amino groups and with characteristic acidity sensitivity, exhibited high relative quantum yields of 25.2% and an optimal emission wavelength of 567 nm. The N-CQDs fluorescence quenching upon the dissociated hydrogen ions (H⁺) in milk and their reacting with the amino groups produced an excellent linear relation (R² = 0.996) between the fluorescence intensity and the milk acidity, which indicated that the fluorescence of the N-CQDs was highly correlated with milk freshness. Furthermore, a fluorescence sensor was designed by depositing the N-CQDs on filter-papers and starch-gel films, to provide eye-readable signals under UV light. A fluorescence colorimetric card was developed, based on the decrease in fluorescence brightness as freshness deteriorated. With the advantages of high sensitivity and eye readability, the proposed sensor could detect spoiled milk in advance and without any preprocessing steps, offering a promising method of assessing food safety.

Abda E. Recent advances and prospects for industrial waste management and product recovery for environmental appliances

Any material when utilized for a required period of time and segment, the leftover residues of those materials are known as waste. Enormous waste is generated during such wear and tear process of materials depending on the usage and functions in a routine lifestyle. Those generated waste when overloaded beyond the capacity of natural recycling processes, would influence the environment and human health. Hence, the waste generated from used materials should be managed according to the environmental impact. Even though wastes are also sometimes rich in organic compounds, nutrients, and energy resources, they are not experimented and managed appropriately. Recently, different feasible techniques are invented and followed to recover and reuse the efficient resources that can create and support sustainable livelihood by creating green economy effects by reducing waste. In this chapter, the emphasis has been given to providing an overview of recent advancements on bio-based waste management and product recoveries such as microbes mediated approaches, biorefineries for waste valorization, and bioenergy from industrial waste.

Recent Advances in the Mechanisms and Regulation of QS in Dairy Spoilage by Pseudomonas spp

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.

Simplified Approach to Predict Food Safety through the Maximum Specific Bacterial Growth Rate as Function of Extrinsic and Intrinsic Parameters

Currently, we assist the emergence of sensors and low-cost information and communication technologies applied to food products, in order to improve food safety and quality along the food chain. Thus, it is relevant to implement predictive mathematical modeling tools in order to predict changes in the food quality and allow decision-making for expiration dates. To perform that, the Baranyi and Roberts model and the online tool Combined Database for Predictive Microbiology (Combase) were used to determine the factors that define the growth of different bacteria. These factors applied to the equation that determines the maximum specific growth rate establish a relation between the bacterial growth and the intrinsic and extrinsic factors that define the bacteria environment. These models may be programmed in low-cost wireless biochemical sensor devices applied to packaging and food supply chains to promote food safety and quality through real time traceability.