Reduction of spoilage of chilled vacuum-packed lamb by psychrotolerant clostridia

Bacterial species diversity of traditionally ripened sheep legs from the Faroe Islands (skerpikjøt)

Skerpikjøt is a traditionally ripened sheep leg product from the Faroe Islands, constituting a relatively underexplored microbial ecosystem. The objective of this study is to achieve a deeper understanding of the microbial composition of this artisanal product. Nine ripened hind legs, obtained from three different producers, were assessed regarding their bacterial communities and contents of biogenic amines, including both surface and core samples. Biogenic amine concentrations were generally low, although one sample had a somewhat elevated concentration of cadaverine. Bacterial diversity was investigated by culture-dependent and culture-independent techniques. Gram-positive catalase-positive cocci (GCC) constituted the most abundant group. Within this group, Staphylococcus equorum was the most prevailing species, followed by Kocuria sp., Mammaliicoccus vitulinus, and Staphylococcus saprophyticus. Lactic acid bacteria prevailed in only one sample and were mainly represented by Latilactobacillus curvatus. Enterobacterial communities were characterised by the prevalence of Serratia proteamaculans. Despite the majority of GCC, Clostridium putrefaciens was the most abundant bacterial species in some core samples. Taken together, the culture-dependent and culture-independent identification methods gave complementary results.

Synergistic Effect of Static Magnetic Field and Modified Atmosphere Packaging in Controlling Blown Pack Spoilage in Meatballs

This study aimed to compare the microbial diversity in meatballs with or without blown pack spoilage (BPS) to determine the cause of BPS and to assess the synergistic effect of static magnetic field (SMF) and modified atmosphere packaging (MAP) to reduce the phenomenon of BPS. Results showed that the BPS group with a 2.26-fold larger volume and packaging containing 71.85% CO₂ had Klebsiella spp. (46.05%) and Escherichia spp. (39.96%) as the dominant bacteria, which was different from the spoilage group. The results of isolation and identification of strains from the BPS group and their inoculation test confirmed that Klebsiella pneumoniae was the major strain-inducing BPS in meatballs due to its pack-swelling ability. SMF (5 mT) treatment combined with MAP (40%CO₂ + 60%N₂), which did not influence the sensory quality of meatballs, had a significant synergistic effect on preventing the increase in pack volume. Compared with the control group, this synergistic treatment effectively delayed bacterial growth, drop in pH, and the increase of TBARS. The findings of this study will provide further guidance for meatball manufacturers to adopt effective strategies to reduce the BPS of meatballs.

Comparative Genome Analysis and Phenotypic Characterization of Clostridium gasigenes CGAS001 Isolated From Chilled Vacuum-Packed Lamb Meat

Genomic data for psychrophilic bacteria causing blown pack spoilage (BPS) are limited. This study characterizes the genome of a novel Clostridium gasigenes strain CGAS001 isolated from meat juice sample (MJS) of vacuum-packed lamb meat by comparing it with the type strain C. gasigenes DSM 12272 and five strains representing four other BPS-causing Clostridium sensu stricto species. Phenotypic characteristics of the strain, which include biochemical characteristics, antimicrobial resistance and production of putative polyketide, have been determined. The size of its draft genome is 4.1 Mb with 3,845 coding sequences, 28.7% GC content and 95 RNA genes that include 75 tRNAs, 17 rRNAs, and 3 ncRNAs. Average Nucleotide Identity (ANI) and digital DNA-DNA Hybridization (dDDH) predict that C. gasigenes CGAS001 and DSM 12272 constitute a single species (ANI and dDDH = 98.3% for speciation) but two distinct subspecies (dDDH = 73.3% for subspeciation). The genome is characterized by saccharolytic, lipolytic and proteolytic genes as well as hemolysins and phospholipases, which are consistent with its phenotype. The genome also reveals the ability of C. gasigenes to synthesize polyketides which is demonstrated by the antimicrobial activity of a crude polyketide extract against Listeria monocytogenes and Enterococcus devriesei. The strain is resistant to polymyxin B and streptomycin. The genetic and phenotypic analyses suggest that CGAS001 constitutes a novel subspecies of C. gasigenes adapted to a saprophytic lifestyle and can synthesize narrow spectrum antimicrobial compounds.

Understanding spoilage microbial community and spoilage mechanisms in foods of animal origin

The increasing global population has resulted in increased demand for food. Goods quality and safe food is required for healthy living. However, food spoilage has resulted in food insecurity in different regions of the world. Spoilage of food occurs when the quality of food deteriorates from its original organoleptic properties observed at the time of processing. Food spoilage results in huge economic losses to both producers (farmers) and consumers. Factors such as storage temperature, pH, water availability, presence of spoilage microorganisms including bacteria and fungi, initial microbial load (total viable count-TVC), and processing influence the rate of food spoilage. This article reviews the spoilage microbiota and spoilage mechanisms in meat and dairy products and seafood. Understanding food spoilage mechanisms will assist in the development of robust technologies for the prevention of food spoilage and waste.

Identification of Clostridium spp. derived from a sheep and cattle slaughterhouse by matrix-assisted laser desorption and ionization-time of flight mass spectrometry (MALDI-TOF MS) and 16S rDNA sequencing

Clostridia are widespread and some of them are serious human pathogens. Identification of Clostridium spp. is important for managing microbiological risks in the food industry. Samples derived from sheep and cattle carcasses from a slaughterhouse in Iran were analyzed by MALDI-TOF MS using direct transfer and extended direct transfer sample preparation methods and 16S rDNA sequencing. MALDI-TOF MS could identify ten species in 224 out of 240 Clostridium isolates. In comparison to the 16S rDNA sequencing, correct identification rate of the Clostridium spp. at the species level by MALDI-TOF MS technique was 93.3%. 16 isolates were not identified by MALDI-TOF MS but 16s rDNA sequencing identified them as C. estertheticum, C. frigidicarnis, and C. gasigenes species. The most frequently identified Clostridium species were: C. sporogenes (13%), C. cadaveris (12.5%), C. cochlearium (12%) and C. perfringens (10%). Extended direct transfer method [2.26 ± 0.18 log (score)] in comparison to direct transfer method [2.15 ± 0.23 log (score)] improved Clostridium spp.

IDENTIFICATION

Using a cut-off score of 1.7 was sufficient for accurate identification of Clostridium species. MALDI-TOF MS identification scores for Clostridium spp. decreased with longer incubation time. Clostridium species predominantly were isolated from carcasses after skinning and evisceration steps in the slaughterhouse. MALDI-TOF MS could be an accurate way to identify Clostridium species. Moreover, continuous improvement of the database and MALDI-TOF MS instrument enhance its performance in food control laboratories.

An investigation of the effect of rapid slurry chilling on blown pack spoilage of vacuum-packaged beef primals

The aim of this study was to investigate if rapid slurry chilling would retard or prevent blown pack spoilage (BPS) of vacuum-packaged beef primals. Beef primals were inoculated with Clostridium estertheticum subspp. estertheticum (DSMZ 8809), C. estertheticum subspp. laramenise (DSMZ 14864) and C. gasigenes (DSMZ 12272), and vacuum-packaged with and without heat shrinkage (90°C for 3 s). These packs were then subjected to immediate chilling in an ice slurry or using conventional blast chilling systems and stored at 2°C for up to 100 days. The onset and progress of BPS was monitored using the following scale; 0-no gas bubbles in drip; 1-gas bubbles in drip; 2-loss of vacuum; 3-'blown'; 4-presence of sufficient gas inside the packs to produce pack distension and 5-tightly stretched, 'overblown' packs/packs leaking. Rapid slurry chilling (as compared to conventional chilling) did not significantly affect (P > 0.05) the time to the onset or progress of BPS. It was therefore concluded that rapid chilling of vacuum-packaged beef primals, using an ice slurry system, may not be used as a control intervention to prevent or retard blown pack spoilage.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study adds to our growing understanding of blown pack spoilage of vacuum-packaged beef primals and suggests that rapid chilling of vacuum-packaged beef primals is not a control option for the beef industry. The results suggest that neither eliminating the heat shrinkage step nor rapid chilling of vacuum-packaged beef retard the time to blown pack spoilage.