Antimicrobial effects ofZataria multifloraessential oil andLactobacillus acidophilusonEscherichia coliO157 stability in the Iranian probiotic white-brined cheese

Use of Starter Cultures in Foods from Animal Origin to Improve Their Safety

Starter cultures can be defined as preparations with a large number of cells that include a single type or a mixture of two or more microorganisms that are added to foods in order to take advantage of the compounds or products derived from their metabolism or enzymatic activity. In foods from animal origin, starter cultures are widely used in the dairy industry for cheese, yogurt and other fermented dairy products, in the meat industry, mainly for sausage manufacture, and in the fishery industry for fermented fish products. Usually, microorganisms selected as starter culture are isolated from the native microbiota of traditional products since they are well adapted to the environmental conditions of food processing and are responsible to confer specific appearance, texture, aroma and flavour characteristics. The main function of starter cultures used in food from animal origin, mainly represented by lactic acid bacteria, consists in the rapid production of lactic acid, which causes a reduction in pH, inhibiting the growth of pathogenic and spoilage microorganisms, increasing the shelf-life of fermented foods. Also, production of other metabolites (e.g., lactic acid, acetic acid, propionic acid, benzoic acid, hydrogen peroxide or bacteriocins) improves the safety of foods. Since starter cultures have become the predominant microbiota, it allows food processors to control the fermentation processes, excluding the undesirable flora and decreasing hygienic and manufacturing risks due to deficiencies of microbial origin. Also, stater cultures play an important role in the chemical safety of fermented foods by reduction of biogenic amine and polycyclic aromatic hydrocarbons contents. The present review discusses how starter cultures contribute to improve the microbiological and chemical safety in products of animal origin, namely meat, dairy and fishery products.

Effects of Essential Oils on Escherichia coli Inactivation in Cheese as Described by Meta-Regression Modelling

The growing intention to replace chemical food preservatives with plant-based antimicrobials that pose lower risks to human health has produced numerous studies describing the bactericidal properties of biopreservatives such as essential oils (EOs) in a variety of products, including cheese. This study aimed to perform a meta-analysis of literature data that could summarize the inactivation of Escherichia coli in cheese achieved by added EOs; and compare its inhibitory effectiveness by application method, antimicrobial concentration, and specific antimicrobials. After a systematic review, 362 observations on log reduction data and study characteristics were extracted from 16 studies. The meta-regression model suggested that pathogenic E. coli is more resistant to EO action than the non-pathogenic type (p < 0.0001), although in both cases the higher the EO dose, the greater the mean log reduction achieved (p < 0.0001). It also showed that, among the factual application methods, EOs' incorporation in films render a steadier inactivation (p < 0.0001) than when directly applied to milk or smeared on cheese surface. Lemon balm, sage, shallot, and anise EOs showed the best inhibitory outcomes against the pathogen. The model also revealed the inadequacy of inoculating antimicrobials in cheese purposely grated for performing challenge studies, as this non-realistic application overestimates (p < 0.0001) the inhibitory effects of EOs.

Chitosan coatings incorporated with propolis extract and Zataria multiflora Boiss oil for active packaging of chicken breast meat

The impact of dipping in combination of propolis extract (PE) and chitosan (CH) coating enriched with Zataria multiflora essential oil (ZEO) on chemical, microbial and organoleptic properties of poultry meat was determined at 4 °C. GC-MS analysis showed that the most components of PE were Dihydrochrysin (9.69%) and b- Pinostrobin (7.41%). The results of mesophilic total viable plate counts (TVC), lactic acid bacteria (LAB), Psychotropic bacteria and Pseudomonas spp. showed detectably lower (p < 0.05) microbial count in CH-PE 1%-Z 0.5% and CH-PE 1%-Z 1% samples at the last day of storage. The results of chemical characteristics (pH, total volatile base nitrogen (TVB-N), 2-thiobarbituric acid reactive substances (TBARS)) in all treated samples compared with the control, revealed that there is a synergistic effect between CH, PE and ZEO. In the sensorial assessment, treatments containing 1% PE- 0.5% ZEO and 1% PE- 1% ZEO were mostly acceptable by the sensory analyst. These results offer a successful approach that chitosan coating enriched with combination of ZEO and PE can be an improving method to reducing deterioration of fresh packed chicken meat.

Gouda cheese spoilage prevention: Biodegradable coating induced by Bunium persicum essential oil and lactoperoxidase system

This study aimed to prepare an inhibitory edible coating for Gouda cheese based on whey protein containing lactoperoxidase system (LPOS) and Bunium persicum essential oil (EO) in order to control postpasteurization contamination. Using a full factorial design, the effects of LPOS and EO on microbiological characteristics and chemical indices of manufactured Gouda cheeses were evaluated during 90 days of storage time. Listeria, lactic acid bacteria, Enterobacter, Escherichia, and Pseudomonas species were considered as potential pathogenic and spoilage indicators of produced Gouda cheese samples. Chemical properties of cheeses were assessed using the free fatty acid, peroxide value, and thiobarbituric acid experiments. The results showed that bacteria counts remained constant in cheese samples coated with EO and also EO-LPOS. However, the survival of gram-positive lactic acid bacteria and Enterobacter spp. was more pronounced in LPOS-based coating. The most effective treatments on oxidation stability parameters in cheese samples were EO- and EO-LPOS coatings. By the addition of B. persicum EO and LPOS, further inhibition of the lipid oxidation of the cheese samples was achieved. Lipolysis, as a result of lipid degradation, was more pronounced in the control, whey-coated, and whey-LPOS-coated samples in comparison with whey-EO- and whey-EO-LPOS-coated samples during the final days of storage time. These results indicate that antibacterial, lipid oxidation, and oxygen barrier properties of the coatings were developed by the addition of B. persicum EO and LPOS.