Selected Spoilage Bacteria Research Articles

Evaluation of Antibacterial Activity of Lactic Acid Bacteria Isolated from Kunun Zaki against Selected Bread Rope Spoilage Bacteria

In line with increasing demand by consumers for safe and minimally processed food products, biopreservation has been advocated over the traditional use of chemical additives in combating food spoilage. This study evaluated the antibacterial activity of four lactic acid bacteria (LAB) (Lactobacillus fermentum, Lactococcus lactis, Lactobacillus brevis and Lactobacillus plantarum) isolated from kunun-zaki against the bread rope spoilage bacteria, Bacillus subtilis and Bacillus cereus. Antibacterial activity was determined using the dual agar overlay method with subsequent measurement of zones of inhibition. Titrimetric methods were used to determine the abilities of the isolated LAB to produce antimicrobials including lactic acid, hydrogen peroxide and diacetyl. Lactobacillus fermentum brought about the highest inhibition zone (20 mm) against Bacillus cereus. The smallest zone of inhibition (6 mm) was recorded for L. plantarum against B. cereus. Whereas L. plantarum produced the highest amount of lactic acid (0.540 g/L), L. brevis produced the lowest lactic acid amount of 0.348 g/L. L. fermentum produced the highest amount of hydrogen peroxide (0.020 g/L) whereas L.brevis recorded the lowest hydrogen peroxide production of 0.010 g/L. L. lactis and L. fermentum had the highest and lowest values of 0.649 g/L and 0.219 g/L respectively for diacetyl production. Differences in the antibacterial activities and antimicrobials production by the LAB were statistically significant (P < .05). The findings show that the LAB isolates possessed antibacterial activity against the selected spoilage bacteria and as such could be exploited as potential biocontrol agents against the selected bread rope spoilage bacteria.

Assessment of the protective culture potential of the Lactococcus lactis Ganee-5 strain as a preservative against spoilage bacteria in tomato pastes

This study investigated the spoilage patterns and biopreservation of tomato paste by lactic acid bacteria isolated from fermented milk products. All the isolates were screened for hydrogen peroxide, diacetyl, and lactic acid production. Isolate with the highest mean values of evaluating parameters was selected as protective culture for the biopreservation. The isolate was identified as Lactococus lactis strain Ganee-5 using molecular techniques, and the sequences were submitted to the Genbank Database to obtain the accession number (MH571417). Antimicrobial properties of the protective culture were evaluated against some selected spoilage bacteria E. coli (ATCC 25922), Listeria monocytogenes (ATCC 15313), Salmonella typhimurium (IFO 12529), and Staphylococcus aureus (ATCC 12600), Varying zone of inhibitions ranged from 18-25 mm were detected. The potato paste was preserved with L. lactis culture, sodium benzoate and control samples while the control samples were left without preservatives. All the experimental set-up was left for 16 days. Physicochemical and nutritional showed that tomato paste with L. lactis was preserved closely as much as sodium benzoate (p< 0.005). Therefore, L. lactis can be adopted for the preservation of the tomato paste to replace chemical preservatives.

Zero-Waste Approach Applied to Pomegranates for Prolonging Fish Burger Shelf Life.

In this study, the possibility of using whole pomegranate (juice, peel and seeds) according to the zero-waste approach, to prolong fresh fish shelf life, was evaluated. A preliminary antimicrobial in vitro test was carried out with peel and seeds as ground and re-ground powders. Then, the entire fruit, in the right proportions of juice and relative by-products as ground or re-ground powders, was added to fresh fish burger formulation to extend its shelf life. To this aim, a shelf-life test was performed on fortified fish products stored at 4 °C. Control samples were also tested for comparison. Specifically, the pH and microbiological and sensory quality of all the fish burgers were monitored during refrigerated storage for about 1 month. The results from the in vitro test clearly indicate that the peel is abundantly more effective than seeds on selected spoilage bacteria and that the ground peel powder is slightly more antimicrobial than the same re-ground powder. Results from the shelf-life test assessed that the control sample became unacceptable within a few days (about 3 days), while the samples with pomegranate juice and by-products maintained microbial stability for a longer time (2 or 3 weeks) (p < 0.05). The main microbiological problems are the proliferations of mesophilic and psychrotrophic bacteria, Pseudomonas spp. and Shewanella. The addition of pomegranate to the formulation allowed the fish spoilage to be controlled by at least 2 or 3 log cycles. In agreement with findings from the in vitro test, the best results from the microbiological point of view were found in fish burgers with juice, peel and seed ground powders. Furthermore, the addition of pomegranate was also appreciated from the sensorial point of view. In fact, products with pomegranate were prized for about 3 weeks for color, odor, appearance and texture of both raw and cooked products. Therefore, the current study reveals that the incorporation of the entire pomegranate, added in all parts according to the zero-waste concept, could promote a significant shelf-life extension of fish burgers, mainly due to the bioactive compounds present in fruit by-products, without changing the sensory quality.

Synergistic effect of essential oils and enterocin KT2W2G on the growth of spoilage microorganisms isolated from spoiled banana peel

The deterioration of fresh food by spoilage microorganisms remains a significant problem even though a diversity of preservation approaches has been proposed. The consumer's choice is demanding for chemical and antimicrobial-free products, which has prompted the development of natural alternatives to retard food spoilage. This study was performed to evaluate the effect of the combination of essential oils (EOs) (orange, tea tree, citronella grass and cinnamon) and enterocin KT2W2G against spoilage microorganisms isolated from the surface of spoiled banana (Musa ABB cv. Kluai “Namwa”) peel by using the agar well diffusion assay. Eighteen spoilage microorganisms (9 strains of bacteria and 9 strains of yeast) were selected as indicator strains. They were identified based on partial 16S rDNA and 18S rDNA gene sequencing for bacteria and yeast, respectively. Selected spoilage bacteria were identified as Lactococcus lactis subsp. lactis, Enterococcus faecalis, Klebsiella pneumonia, Klebsiella variicola and Serratia marcescens, whereas selected spoilage yeast were identified as Kodamaea ohmeri, Pichia aff. fermentans, Pichia kudriavzevii, Hanseniaspora opuntiae and Candida metapsilosis. The agar well diffusion assays resulted in cinnamon as being the most effective EO against selected spoilage indicator. The combination of cinnamon oil and enterocin KT2W2G at 6:4 ratios exhibited the best synergistic effect against selected spoilage microorganisms, whereas enterocin KT2W2G applied as single substance displayed no activity. The results obtained indicate that the combination of cinnamon oil with enterocin KT2W2G harbours the potential to be used as a natural biocontrol agent to improve food quality and to extend the shelf life of harvested bananas.

Shelf-Life of Eviscerated Broiler Carcasses as Affected by Vacuum Packaging and Potassium Sorbate

Packaging chicken carcasses under vacuum and pretreating with potassium sorbate (VS), under vacuum without pretreating with potassium sorbate (V) or under air atmosphere after pretreating with potassium sorbate (CS), as compared with conventional packaging under air atmosphere (control) showed that the spoilage bacterial counts during storage at 4°C exceeded the upper limit of log 7.2 cfu/mL for the control by 25-26, 14-15 and 13-14 d after processing, and at 7°C by 16, 11 and 10-11 d respectively. These data indicated that a combination of vacuum packaging and sorbate dip can extend the shelf-life of poultry carcasses over those conventionally-packaged by an extra 18-19, 6-7 and 7-8 d at 4°C, and 9, 4 and 3-4 d at 7°C, respectively. Under these conditions, the levels of Enterobacteriaceae were not affected substantially by either vacuum packaging or vacuum + potassium sorbate, although these levels were relatively lower than those reported using conventional packaging. The increased levels of total volatile nitrogen and decreased level of extract release volume confirmed the positive relationship between these values and the bacterial counts of spoilage. The occurrence of certain selected spoilage bacteria, such as Pseudomonas and Lactobacillus, was substantially higher in air packaged carcasses (more at 7 then at 4°C) than in vacuum packaged ones, whereas Lactobacillus were predominant under vacuum conditions, independent of sorbate treatment.

Influence of Phosphate and Glucose Addition on some Important Spoilage Bacteria in Vacuum Packed Bologna-Type Sausage

Studies were done on the influence of phosphate and glucose addition on some selected spoilage bacteria in vacuum packed sliced bologna-type sausage during refrigerated storage. Batches with low pH phosphate mixture or sodium tripolyphosphate were used along with batches without phosphate addition. Addition of low pH phosphate had a pronounced influence on Brochothrix thermosphacta and Serratia liquefaciens, while the influence of glucose addition on these bacteria was small. No marked effect of phosphate type could be observed with the lactic acid bacteria, but the most profound growth happened in sausages without phosphate, and at 2°C was stimulated by glucose addition. Lactic acid accumulated more rapidly in batches without phosphate addition.