Insights into the current evidence on the effects of essential oils toward beneficial microorganisms in foods with a special emphasis to lactic acid bacteria – A review

Antimicrobial potential of oregano essential oil vehiculated in Pickering cellulose nanofibers-stabilized emulsions

Essential oils show several biological properties, such as antimicrobial activity, but have limitations regarding their availability and stability. To maximize their antimicrobial effect and protection against environmental conditions, Pickering-type emulsions were used to vehiculate oregano essential oil (OEO) using cellulose nanofibers (CNF) as emulsion stabilizer. Enzymatic hydrolysis was used to produce CNF from a food industry waste (cassava peel), obtaining an environmentally sustainable emulsion stabilizer. It was evaluated how the different properties of the nanofibers affected the stability of the emulsions. Furthermore, the composition of the dispersed phase was varied (different ratios of OEO and sunflower oil-SO) in view of the target application in biodegradable active coatings. Even at very low concentration (0.01 % w/w), CNF was able to form kinetically stable emulsions with small droplet sizes using oil mixtures (OEO + SO). The stabilization mechanism was not purely Pickering, as there was a reduction in interfacial tension. Excellent antimicrobial activity was observed against bacteria and the fungus Alternaria alternata, demonstrating the ability to apply these emulsions in active systems such as coatings and films. An improvement in the stability of emulsions was observed when using a mixture of oils, which is extremely advantageous considering costs and stability to heat treatments, since the desired antimicrobial activity is maintained for the final application.

The inhibitory effects of plant additives on biogenic amine formation in fermented foods - a review

Fermented food has unique properties and high nutritional value, and thus, should constitute a basic element of a balanced and health-promoting diet. However, it can accumulate considerable amount of biogenic amines (BAs), which ingested in excess can lead to adverse health effects. The application of plant-derived additives represents a promising strategy to ensure safety or enhance the functional and organoleptic properties of fermented food. This review summarizes currently available data on the application of plant-origin additives with the aim to reduce BA content in fermented products. The importance of ensuring fermented food safety has been highlighted considering the growing evidence of beneficial effects resulting from the consumption of this type of food, as well as the increasing number of individuals sensitive to BAs. The examined plant-origin additives reduced the BA concentration to varying degrees, and their efficacy depended on the type of additive, matrix, autochthonous, and inoculated microorganisms, as well as the manufacturing conditions. The main mechanisms of action include antimicrobial effects and the inhibition of microbial decarboxylases. Further research on the optimization of bioactive substances extraction, standardization of their chemical composition, and development of detailed procedures for its use in fermented products manufacturing are needed.

Rosmarinus officinalis L. Essential Oils Impact on the Microbiological and Oxidative Stability of Sarshir (Kaymak)

This study investigated the effect of Rosmarinus officinalis L. essential oil, REO (one, two and three percent) on the microbiological and oxidative stability of Sarshir during 20 days of refrigerated storage (4 °C). Initially, the chemical composition (gas chromatography/mass spectrometry, GC/MS), antimicrobial (paper disc diffusion) and antioxidant (DPPH) properties of REO were evaluated. Then, the microbial safety, oxidative stability (peroxide and anisidine values) and overall acceptability of the product after addition of REO to Sarshir and the subsequent storage period were determined. According to GC/MS analysis, the major components of REO were α-pinene (24.6%), 1,8-cineole (14.1%), camphor (13.5%), camphene (8.1%) and limonene (6.1%), respectively. Moreover, it was also found that Limosilactobacillus fermentum (inhibition zone (IZ) of 23.5 mm) and Salmonella Typhi (IZ of 16.4 mm) were the most sensitive and resistant spoilage and pathogenic bacteria against REO, respectively. In addition, the half-maximal inhibitory concentration (IC50) of the REO was measured at 24.8 mg/mL, while the IC50 value of butylated hydroxytoluene (BHT) was 16.6 mg/mL. The highest and lowest bacterial populations were detected in the control and the sample containing 3% REO, respectively. The control had the highest extent of lipid oxidation, while the lowest peroxide and anisidine values were measured in Sarshir containing 3% REO.

Mycotoxin Contamination Status of Cereals in China and Potential Microbial Decontamination Methods

The presence of mycotoxins in cereals can pose a significant health risk to animals and humans. China is one of the countries that is facing cereal contamination by mycotoxins. Treating mycotoxin-contaminated cereals with established physical and chemical methods can lead to negative effects, such as the loss of nutrients, chemical residues, and high energy consumption. Therefore, microbial detoxification techniques are being considered for reducing and treating mycotoxins in cereals. This paper reviews the contamination of aflatoxins, zearalenone, deoxynivalenol, fumonisins, and ochratoxin A in major cereals (rice, wheat, and maize). Our discussion is based on 8700 samples from 30 provincial areas in China between 2005 and 2021. Previous research suggests that the temperature and humidity in the highly contaminated Chinese cereal-growing regions match the growth conditions of potential antagonists. Therefore, this review takes biological detoxification as the starting point and summarizes the methods of microbial detoxification, microbial active substance detoxification, and other microbial inhibition methods for treating contaminated cereals. Furthermore, their respective mechanisms are systematically analyzed, and a series of strategies for combining the above methods with the treatment of contaminated cereals in China are proposed. It is hoped that this review will provide a reference for subsequent solutions to cereal contamination problems and for the development of safer and more efficient methods of biological detoxification.

Recent development in the preservation effect of lactic acid bacteria and essential oils on chicken and seafood products

Chicken and seafood are highly perishable owing to the higher moisture and unsaturated fatty acids content which make them more prone to oxidation and microbial growth. In order to preserve the nutritional quality and extend the shelf-life of such products, consumers now prefer chemical-free alternatives, such as lactic acid bacteria (LAB) and essential oils (EOs), which exert a bio-preservative effect as antimicrobial and antioxidant compounds. This review will provide in-depth information about the properties and main mechanisms of oxidation and microbial spoilage in chicken and seafood. Furthermore, the basic chemistry and mode of action of LAB and EOs will be discussed to shed light on their successful application in chicken and seafood products. Metabolites of LAB and EOs, either alone or in combination, inhibit or retard lipid oxidation and microbial growth by virtue of their principal constituents and bioactive compounds including phenolic compounds and organic acids (lactic acid, propionic acid, and acetic acid) and others. Therefore, the application of LAB and EOs is widely recognized to extend the shelf-life of chicken and seafood products naturally without altering their functional and physicochemical properties. However, the incorporation of any of these agents requires the optimization steps necessary to avoid undesirable sensory changes. In addition, toxicity risks associated with EOs also demand the regularization of an optimum dose for their inclusion in the products.

Recent advance in technological innovations of sugar-reduced products

Sugar is crucial as an essential nutrient for humans as well as for providing texture, sweetness and so on to food. But with the rise in people's pursuit of health, it is becoming increasingly clear that excessive consumption of sugar can locate a load on the body. It has been that excessive sugar is associated with many diseases, such as dental caries, obesity, diabetes, and coronary heart disease. Therefore, researchers and industries are trying to reduce or substitute sugar in food without affecting the sensory evaluation. Substituting sugar with sweeteners is alternatively becoming the most traditional way to minimize its use. So far, the sweeteners such as stevia and xylitol have been are commercially applied. Several studies have shown that technological innovation can partially compensate for the loss in sweetness as a result of sugar reduction, such as cross-modal interactions that stimulate sweetness with aroma, nanofiltration that filters disaccharides and above, enzyme-catalyzed sugar hydrolysis, and microbial fermentation that turns sugar into sugar alcohol. This review summarizes these studies to enhance the safety and quality of sugar-reduced products, and will provide some theoretical frameworks for the food industry to reduce sugar in foods, meet consumers' needs, and promote human health.

Formation of cinnamon essential oil/xanthan gum/chitosan composite microcapsules basing on Pickering emulsions

Cinnamon essential oil (CNO) is a natural and renewable antibacterial agent. However, CNO is highly volatile and unstable, which limits its practical application as a long-term and wide antibacterial agent. In order to improve the CNO stability, we have microencapsulated CNO into composite microcapsules basing on Pickering emulsion stabilized by silica (SiO₂) nanoparticles. The CNO-loaded composite microcapsules possess the hybrid microcapsule shell including SiO₂, xanthan gum and chitosan. Moreover, the results show that the microcapsules have spherical appearance. Microencapsulation technique effectively promotes the CNO stability, and the loaded CNO is slowly released from microcapsules. The antibacterial test indicates that the minimal inhibitory concentration of microcapsules was 2 mg mL⁻¹ against Escherichia coli and Staphylococcus aureus, and the microcapsules can play an effective long-term antibacterial effect. Thus, Pickering emulsion templates is a convenient and effective technique to construct antibacterial essential oil-contained microcapsules, which can be used as long-term antibacterial agents.

Protective Impact of Chitosan Film Loaded Oregano and Thyme Essential Oil on the Microbial Profile and Quality Attributes of Beef Meat

Edible films and essential oil (EO) systems have the potency to enhance the microbial quality and shelf life of food. This investigation aimed to evaluate the efficacy of chitosan films including essential oils against spoilage bacteria and foodborne pathogens associated with meat. Antimicrobial activity (in vitro and in vivo) of chitosan films (CH) incorporated with oregano oil (OO) and thyme oil (TO) at 0.5 and 1% was done against spoilage bacteria and foodborne pathogens, compared to the control sample and CH alone. Preliminary experiments (in vitro) showed that the 1% OO and TO were more active against Staphylococcus aureus compared to Escherichia coli O157:H7 and Salmonella Typhimurium. In in vivo studies, CH containing OO and TO effectively inhibited the three foodborne pathogens and spoilage bacteria linked with packed beef meat which was kept at 4 °C/30 days compared to the control. The total phenolic content of the EOs was 201.52 mg GAE L⁻¹ in thyme and 187.64 mg GAE L⁻¹ in oregano. The antioxidant activity of thyme oil was higher than oregano oil. The results demonstrated that the shelf life of meat including CH with EOs was prolonged ~10 days compared to CH alone. Additionally, CH-OO and CH-TO have improved the sensory acceptability until 25 days, compared to the control. Results revealed that edible films made of chitosan and containing EOs improved the quality parameters and safety attributes of refrigerated or fresh meat.