Natural Antimicrobials in Dairy Products: Benefits, Challenges, and Future Trends

This review delves into using natural antimicrobials in the dairy industry and examines various sources of these compounds, including microbial, plant, and animal sources. It discusses the mechanisms by which they inhibit microbial growth, for example, by binding to the cell wall's precursor molecule of the target microorganism, consequently inhibiting its biosynthesis, and interfering in the molecule transport mechanism, leading to cell death. In general, they prove to be effective against the main pathogens and spoilage found in food, such as Escherichia coli, Staphylococcus aureus, Bacillus spp., Salmonella spp., mold, and yeast. Moreover, this review explores encapsulation technology as a promising approach for increasing the viability of natural antimicrobials against unfavorable conditions such as pH, temperature, and oxygen exposure. Finally, this review examines the benefits and challenges of using natural antimicrobials in dairy products. While natural antimicrobials offer several advantages, including improved safety, quality, and sensory properties of dairy products, it is crucial to be aware of the challenges associated with their use, such as potential allergenicity, regulatory requirements, and consumer perception. This review concludes by emphasizing the need for further research to identify and develop effective and safe natural antimicrobials for the dairy industry to ensure the quality and safety of dairy products for consumers.

Exploring the association between a standardized extract of pequi peels (Caryocar brasiliense Cambess) and blue light as a photodynamic therapy for treating superficial wounds

Natural products derived from plants can be used as photosensitizers for antimicrobial photodynamic therapy (aPDT) combining key therapeutic strategies for tissue repair while controlling microorganisms' growth. We investigated a standardized extract of pequi peels (Caryocar brasiliense Cambess) as a brownish natural photosensitizer for aPDT using blue light. Three concentrations of the pequi extract (PE; 10, 30, or 90 μg/mL) were tested solely or associated with blue laser (445 nm, 100 mW, 138 J/cm2, 6 J, 60 s). In vitro, we quantified reactive oxygen species (ROS), assessed skin keratinocytes (HaCat) viability and migration, and aPDT antimicrobial activity on Streptococcus or Staphylococcus strains. In vivo, we assessed wound closure for the most active concentration disclosed by the in vitro assay (30 μg/mL). Upon aPDT treatments, ROS were significantly increased in cell monolayers regardless of PE concentration. PE at low doses stimulates epithelial cells. Although PE stimulated cellular migration, aPDT was moderately cytotoxic to skin keratinocytes, particularly at the highest concentration. The antimicrobial activity was observed for PE at the lowest concentration (10 μg/mL) and mostly at PE 10 μg/mL and 30 μg/mL when used as aPDT photosensitizers. aPDT with PE 30 μg/mL presents antimicrobial activity without compromising the initial phases of skin repair.

Application of Agri-Food By-Products in Cheesemaking

Agri-food companies produce large quantities of plant by-products that in many instances contain functional bioactive compounds. This review summarizes the main applications of agro-industrial by-products in cheesemaking, considering their bioactivities and functional properties. Polyphenol-rich by-products increase antioxidant and antimicrobial activity in cheeses, positively impacting their shelf life. Contrasting results have been obtained regarding the color and sensory properties of enriched cheeses depending on the selected by-products and on the technology adopted for the extract preparation. Furthermore, functional compounds in cheeses perform a prebiotic function and their bioavailability improves human health. Overall, the use of agri-food by-products in cheese formulation can offer benefits for agri-food chain sustainability and consumer health.

Bioactive Compounds from Fruits as Preservatives

The use of additives with preservative effects is a common practice in the food industry. Although their use is regulated, natural alternatives have gained more attention among researchers and professionals in the food industry in order to supply processed foods with a clean label. Fruits are essential components in a healthy diet and have also been associated with improved health status and a lower risk of developing diseases. This review aims to provide an overview of the main bioactive compounds (polyphenols, betalain, and terpenes) naturally found in fruits, their antioxidant and antimicrobial activity in vitro, and their preservative effect in different foods. Many extracts obtained from the skin (apple, grape, jabuticaba, orange, and pomegranate, for instance), pulp (such as red pitaya), and seeds (guarana, grape, and jabuticaba) of fruits are of great value due to the presence of multiple compounds (punicalagin, catechin, gallic acid, limonene, β-pinene, or γ-terpinene, for instance). In terms of antioxidant activity, some fruits that stand out are date, jabuticaba, grape, and olive, which interact with different radicals and show different mechanisms of action in vitro. Antimicrobial activity is observed for natural extracts and essential oils (especially from citrus fruits) that limit the growth of many microorganisms (Bacillus subtilis, Escherichia coli, Penicillium digitatum, and Pseodomonas aeruginosa, for instance). Studies in foods have revealed that the use of extracts or essential oils as free or encapsulated forms or incorporated into films and coatings can inhibit microbial growth, slow oxidative reactions, reduce the accumulation of degradative products, and also preserve sensory attributes, especially with films and coatings. Future studies could focus on the advances of extracts and essential oils to align their use with the development of healthier foods (especially for meat products) and explore the inhibition of spoilage microorganisms in dairy products, for instance.

Pequi (Caryocar brasiliense) Waste Extract as a Synergistic Agent in the Microbial and Physicochemical Preservation of Low-Sodium Raw Goat Cheese

The growth of spoilage and pathogenic bacteria during storage represents significant losses in marketing raw milk cheeses. Thus, reducing NaCl in these products is challenging, as sodium has a critical antimicrobial role. Despite advances in non-thermal technologies, the short shelf life still limits the availability of raw goat cheese. Thus, combined preservation methods can be promising because their synergies can extend shelf life more effectively. In this context, Principal Component Analysis (PCA) was applied to variables to investigate the effect of pequi waste extract (PWE), a native Brazilian fruit, combined with UV-C radiation (CEU) and vacuum packaging (CEV) on the preservation of low-sodium raw goat cheese. CEV samples had lower loadings for Staphylococcus subsp. and Enterobacteriaceae than other treatments in PC2, having a count's reduction up to 3-fold (P < 0.05) compared to vacuum alone. In contrast, CEU showed an increase of up to 1.2-fold on staphylococcal count compared to UV-C alone. Still, the addition of PWE to UV-C-treated cheeses resulted in 8.5% protein loss. Furthermore, PWE, especially in CEV, delayed post-acidification during storage. It made CEV up to 4.5 and 1.6-fold more stable for color and texture, respectively than vacuum alone. These data strongly suggest that PWE may be a novel and promising synergistic agent in the microbial and physicochemical preservation of low-sodium raw milk cheese when combined with the vacuum.

Camu-camu [Myrciaria dubia (HBK) McVaugh]: A review of properties and proposals of products for integral valorization of raw material

This review aims to evaluate the production and processing chain of camu-camu (Myrciaria dubia), giving suggestions to maximize the valorization of raw materials, demonstrating new product possibilities from processing to distribution and highlighting the suggested contributions. It is clear that despite the camu-camu pulp has important properties, a large part of its raw material, considered waste (around 50%) and formed by important bioactive compounds, can give rise to new products, such as bioactive extracts to be used by pharmaceutical, chemical and food industries, ingredients for bakery products, dairy and several others sectors, which constitutes opportunities, in addition to contributing to the reduction of agro-industrial waste and the preservation of the environment.

A Systematic Review on Nanoencapsulation Natural Antimicrobials in Foods: In Vitro versus In Situ Evaluation, Mechanisms of Action and Implications on Physical-Chemical Quality

Natural antimicrobials (NA) have stood out in the last decade due to the growing demand for reducing chemical preservatives in food. Once solubility, stability, and changes in sensory attributes could limit their applications in foods, several studies were published suggesting micro-/nanoencapsulation to overcome such challenges. Thus, for our systematic review the Science Direct, Web of Science, Scopus, and Pub Med databases were chosen to recover papers published from 2010 to 2020. After reviewing all titles/abstracts and keywords for the full-text papers, key data were extracted and synthesized. The systematic review proposed to compare the antimicrobial efficacy between nanoencapsulated NA (nNA) and its free form in vitro and in situ studies, since although in vitro studies are often used in studies, they present characteristics and properties that are different from those found in foods; providing a comprehensive understanding of primary mechanisms of action of the nNA in foods; and analyzing the effects on quality parameters of foods. Essential oils and nanoemulsions (10.9–100 nm) have received significant attention and showed higher antimicrobial efficacy without sensory impairments compared to free NA. Regarding nNA mechanisms: (i) nanoencapsulation provides a slow-prolonged release to promote antimicrobial action over time, and (ii) prevents interactions with food constituents that in turn impair antimicrobial action. Besides in vitro antifungal and antibacterial, nNA also demonstrated antioxidant activity—potential to shelf life extension in food. However, of the studies involving nanoencapsulated natural antimicrobials used in this review, little attention was placed on proximate composition, sensory, and rheological evaluation. We encourage further in situ studies once data differ from in vitro assay, suggesting food matrix greatly influences NA mechanisms.