Plants: A natural solution to enhance raw milk cheese preservation?

Indigenous knowledge on the practice of milk container fumigation and its effect on microbial safety of milk among pastoral communities in west Guji zone, southern Ethiopia

Introduction

Milk is a high-risk food and has been implicated in many foodborne illnesses. Thus, the pastoral communities in rural Ethiopia used a traditional practice of milk container fumigation to maintain the quality and safety of milk.

Objective

to assess the indigenous knowledge on milk container fumigation practice and its effect on the microbial safety of milk among pastoral communities in the west Guji zone, southern Ethiopia.

Methods

A cross-sectional study design was conducted in six randomly selected kebeles of the pastoral districts in the west Guji zone, Southern Ethiopia from December to June/2022. The preservative plants and raw milk samples were collected and transported to the laboratory, to analyze the efficacy of plants on the microbial safety throughout milk storage. A variance analysis was used to compare the means of microbiological growth and pH measure among the treatments and control; while thematic analysis was for qualitative data.

Result

Four species of plants, namely: Olea africana, Clerodendrum myricoides (Hochst) vatke, Rhamnus staddo, and Rhus natalensis were identified from the study area; as they were used for fumigating milk storage containers to prevent a contamination of milk. According to respondents, the fumigation of milk containers was practiced by holding the container upside down over the smoke from a burning chip of each plant species. Accordingly, it was demonstrated that the R. staddo has relatively better efficacy in inhibiting microbial growth in milk than O. africana and C. myricoides (Hochst) vatke; while R. natalensis has no significant impact on microbial growth in milk over the storage period.

Conclusion

Pastoralists in the West Guji zone were fumigated the milk storage container by using smoke of O. africana, R. staddo, C. myricoides (Hochst) vatke, and R. natalensis plants. As such, it was identified that R. staddo has relatively better efficacy in inhibiting microbial growth in milk than O. africana and C. myricoides (Hochst) vatke; and it is a better plant to be recommended for the preservation of cow milk.

Mild Heat Treatment and Biopreservatives for Artisanal Raw Milk Cheeses: Reducing Microbial Spoilage and Extending Shelf-Life through Thermisation, Plant Extracts and Lactic Acid Bacteria

The microbial quality of raw milk artisanal cheeses is not always guaranteed due to the possible presence of pathogens in raw milk that can survive during manufacture and maturation. In this work, an overview of the existing information concerning lactic acid bacteria and plant extracts as antimicrobial agents is provided, as well as thermisation as a strategy to avoid pasteurisation and its negative impact on the sensory characteristics of artisanal cheeses. The mechanisms of antimicrobial action, advantages, limitations and, when applicable, relevant commercial applications are discussed. Plant extracts and lactic acid bacteria appear to be effective approaches to reduce microbial contamination in artisanal raw milk cheeses as a result of their constituents (for example, phenolic compounds in plant extracts), production of antimicrobial substances (such as organic acids and bacteriocins, in the case of lactic acid bacteria), or other mechanisms and their combinations. Thermisation was also confirmed as an effective heat inactivation strategy, causing the impairment of cellular structures and functions. This review also provides insight into the potential constraints of each of the approaches, hence pointing towards the direction of future research.

Plant extracts and essential oils in the dairy industry: A review

Plants have been used as food additives worldwide to enhance the sensory qualities of foods and extend their shelf life by reducing or eliminating foodborne pathogens. They also serve as therapeutic agents due to their beneficial effects on human health through their anti-cancerous, anti-inflammatory, antioxidant, and immune-modulatory properties. Plants can be added to food as a dry powder, grated material, paste, juice, or as an extract that can be produced by a variety of methods. Plant extracts and essential oils are concentrated sources of bioactive phytochemicals that can be added to food in small amounts in a variety of forms. These forms include liquid, semi-solid, or dry powder for easy and uniform diffusion. Encapsulation can protect bioactive compounds from temperature, moisture, oxidation, and light, as well as allow for controlling the release of the encapsulated ingredients. Nanoemulsions can enhance the bioactivity of active components. This review explains how plant extracts and essential oils are used in the dairy industry as antimicrobial materials, analyzing their impact on starter bacteria; as natural antioxidants to prevent the development of off-flavors and increase shelf life; and as technological auxiliaries, like milk-clotting enzymes, stabilizers, and flavoring agents. Therefore, plant extracts and essential oils are a better choice for the dairy industry than plants or their parts due to a wide range of applications, homogeneous dispersion, and ability to control the concentration of the bioactive ingredients and enhance their efficiency.

Effect of Bear Garlic Addition on the Chemical Composition, Microbiological Quality, Antioxidant Capacity, and Degree of Proteolysis in Soft Rennet Cheeses Produced from Milk of Polish Red and Polish Holstein-Friesian Cows

This study aimed to assess the effect of milk source and bear garlic addition on the selected properties of soft rennet cheese. Cheeses were produced from cow milk derived from two sources: Polish Red cows (PR) and Polish Holstein-Friesian cows (PHF) with a 0.5% (w/w) addition of bear garlic (Allium ursinum L.) dried leaves. Chemical composition and fatty acid profiles (GC) were determined in fresh cheeses. Fresh and stored for two weeks cheeses were subjected to microbiological studies, i.e., total aerobic bacteria count (TABC); count of Lactococcus sp., yeast and molds; coliforms; analysis of the proteolysis extension by means of o-phthaldialdehyde (OPA) assay and free amino acids content (HPLC); antioxidant capacity as 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidant power (FRAP); as well as pH and water activity. Cheeses with bear garlic herbs were more prone to proteolysis but this was not accompanied by any effect on the microbial counts, water activity or pH. Cheeses produced from PR milk contained less monounsaturated fatty acids (MUFA) but were richer in n-3 PUFA and had a lower n-6/n-3 FA ratio than cheeses from PHF milk. Bear garlic addition increased DPPH anti-radical power but had less of an effect on the FRAP values.

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.

Pomegranate Byproduct Extracts as Ingredients for Producing Experimental Cheese with Enhanced Microbiological, Functional, and Physical Characteristics

Pomegranate peel and mesocarp, considered as wastes of fruit processing, are rich sources of beneficial phytochemicals, including hydrolyzable tannins and flavonoids, with proven antimicrobial and antioxidant activity, which can be employed for improving the overall quality of food products. In the present study, extracts from pomegranate peel (PPW) and mesocarp (PMW) were obtained through a water extraction method and evaluated for in vitro antimicrobial activity and polyphenol content. The two extracts were then added during the cheese-making process in order to create a new functional cheese with improved microbiological and physico-chemical characteristics. Antimicrobial in vitro assays evidenced a substantial efficacy of both extracts against Staphylococcus aureus, which often causes staphylococcal food poisoning outbreaks linked to the consumption of raw milk cheeses and artisanal cheeses. For this reason, a simulated cheese contamination was carried out in order to assess if pomegranate extracts can exert antimicrobial activity towards this pathogen even when incorporated into the cheese matrix. Milk enriched with pomegranate extracts (PPW and PMW) was used to produce two different experimental cheeses, which were then evaluated for yield, polyphenol content, and microbiological as well as physico-chemical traits throughout the refrigerated storage. Despite the low concentration of the extracts, the treated cheeses showed an increase in firmness and a slight decrease in S. aureus counts, of more than one log unit in comparison to the control cheese, for up to 12 d of cold storage. Such results support the reuse of agro-food byproducts, in substitution to chemical food preservatives, as the key to a circular economy.

The physicochemical, microbiological, and organoleptic properties and antioxidant activities of cream cheeses fortified with dried curry leaves (Murraya koenigii L.) powder

We aimed to investigate the effects of dried curry leaves powder (CLP) incorporation on physicochemical, microbiological, antioxidant, and sensory properties of cream cheeses. Varying levels of CLP infusions (i.e., T1: 0% [control], T2: 0.15%, T3: 0.2%, and T4: 0.25%; w/w%) were stored for 10 days at 4°C. Antioxidant properties were evaluated using total phenolic content, 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging ability, and ferric reducing antioxidant power using in vitro assays. Total antioxidant capacity significantly (p < .05) increased with the increasing levels of CLP. Physicochemical and microbiological qualities were not significantly affected by the addition of CLP, indicating the suitability of using CLP without compromising the quality of cream cheese. Organoleptic properties were affected with CLP addition, where T3 had the highest scores for color, aroma, flavor, texture, and overall acceptability. The principal component analysis provides the holistic approach of studying the variation associated with cream cheeses and the overall relationship among studied parameters. This provides strong references for novel dairy products added with antioxidant-rich Murraya koenigii L. powder. The study also has merits to promote scientific knowledge concerning, and how the incorporation would influence the physicochemical, organoleptic, and microbiological properties of cream cheese to deliver the value-added or diversified product to emerging consumers.

Green and Healthier Alternatives to Chemical Additives as Cheese Preservative: Natural Antimicrobials in Active Nanopackaging/Coatings

The side effects and potential impacts on human health by traditional chemical additives as food preservatives (i.e., potassium and sodium salts) are the reasons why novel policies are encouraged by worldwide public health institutes. More natural alternatives with high antimicrobial efficacy to extend shelf life without impairing the cheese physicochemical and sensory quality are encouraged. This study is a comprehensive review of emerging preservative cheese methods, including natural antimicrobials (e.g., vegetable, animal, and protist kingdom origins) as a preservative to reduce microbial cheese contamination and to extend shelf life by several efforts such as manufacturing ingredients, the active ingredient for coating/packaging, and the combination of packaging materials or processing technologies. Essential oils (EO) or plant extracts rich in phenolic and terpenes, combined with packaging conditions and non-thermal methods, generally showed a robust microbial inhibition and prolonged shelf life. However, it impaired the cheese sensory quality. Alternatives including EO, polysaccharides, polypeptides, and enzymes as active ingredients/nano-antimicrobials for an edible film of coating/nano-bio packaging showed a potent and broad-spectrum antimicrobial action during shelf life, preserving cheese quality parameters such as pH, texture, color, and flavor. Future opportunities were identified in order to investigate the toxicological effects of the discussed natural antimicrobials' potential as cheese preservatives.

Supplementation of Double Cream Cheese with Allium roseum: Effects on Quality Improvement and Shelf-Life Extension

This study gives a new insight into the direct supplementation of Allium roseum leaves in double cream cheese. Allium roseum leaves were added to double cream cheese as a powder and a fresh paste. Based on the formulation calculation and on sensory analyses, doses of 6% paste and 0.8% powder were used to formulate the flavored cheeses. The sensory characteristics of the two double cream cheeses were assessed and compared to a plain formula. Cheese samples, stored at 5 °C, were sampled every 0, 4, 8, 12 and 15 days and analyzed for pH, fat, dry contents, yeasts and molds and total coliforms. The positive effects of Allium roseum supplementation, either as a powder or as a fresh paste, have been proven, based on sensorial, physicochemical, and microbiological qualities. The shelf life of cheese samples was also determined through an accelerated shelf life test and the Arrhenius equation. The experiments were conducted at 5, 15, and 25 °C for 15 days. The results showed a significant shelf life extension for flavored double cream cheeses (12 days) versus the plain formula (10 days). The use of Allium roseum leaves, as a natural preservative, seems to be a promising trend for the formulation of similar dairy products.

Proteomics analysis of the bio-functions of Dregea sinensis stems provides insights regarding milk-clotting enzyme

Dregea sinensis (D. sinensis) stems have traditionally been used as milk coagulant in Dali of Yunnan Province, China. In this study, proteomics was used to investigate the bio-functions of D. sinensis stem proteins, leading to the purification and identification of the milk-clotting enzyme. A total of 205 proteins mainly involved in the catalytic and metabolic processes were identified, of which 28 proteins exhibited hydrolase activity. Among the 28 proteins, we focused on two enzymes (M9QMC9 and B7VF65). Based on proteomics, a cysteine protease (M9QMC9) with a molecular weight of 25.8 kDa and milk-clotting activity was purified from D. sinensis stems using double ammonium sulfate precipitation and was confirmed using liquid chromatography-mass spectrometry (LC-MS/MS). The milk-clotting temperature using the purified enzyme was around 80 °C (specific activity at 314.38 U/mg), and it was found to be stable in the pH range of 6-9 in NaCl concentration of <0.8 mol/L. These findings indicated that the enzyme isolated from D. sinensis stems has potential in the dairy and food sectors, especially in the cheese-making industry.

Biodiversity and dairy traits of lactic acid bacteria from foliage of aromatic plants before and after dehydration process monitored by a smart sensors system

The main hypothesis of this work was to evaluate the presence of lactic acid bacteria (LAB) intrinsically resistant to plant essential oils in sage (Salvia officinalis L.) and laurel (Laurus nobilis), for future applications in functional cheese production by addition of aromatic herbs. The effect of the drying process on the viability of LAB was evaluated with three biomass densities (3, 4 and 5 kg/m2). The drying densities did not affect weight loss, but influenced the levels of LAB of sage and laurel. A total of 10 different strains of Enterococcus faecium, Enterococcus mundtii, Enterococcus raffinosus and Leuconostoc mesenteroides were identified from laurel, while sage did not host any LAB species. In particular, L. mesenteroides was the only species sensitive to the heat treatment. Only five strains, all enterococci, were resistant to at least one antibiotic, even though no strain showed gelatinase or haemolytic activity. The investigation on the technological traits useful in cheese making demonstrated that all LAB can be considered non starter LAB, because they were characterized by a slow acidification capacity (the pH was still above 6.00 after 3 d) and a very limited autolysis (the maximum decrease of the optical density at 599 nm was barely 0.2).

Traditional plants from Asteraceae family as potential candidates for functional food industry

Traditional plants have been used in the treatment of disease and pain due to their beneficial properties such as antioxidant, antiinflammation, analgesic, and antibiotic activities. The Asteraceae family is one of the most common groups of plants used in folk medicine. The species Achillea millefolium, Arnica montana, Bellis perennis, Calendula officinalis, Chamaemelum nobile, Eupatorium cannabinum, Helichrysum stoechas, and Taraxacum officinale have been used in different remedies in Northwest Spain. Besides health benefits, some of them like C. nobile and H. stoechas are already employed in cooking and culinary uses, including cocktails, desserts, and savory dishes. This study aimed to review the current information on nutritive and beneficial properties and bioactive compounds of these plants, which are not mainly used as foods but are possible candidates for this purpose. The report highlights their current uses and suitability for the development of new functional food industrial applications. Phenolic compounds, essential oils, and sesquiterpene lactones are some of the most important compounds, being related to different bioactivities. Hence, they could be interesting for the development of new functional foods.

Supercritical Fluid Chromatography development of a predictive analytical tool to selectively extract bioactive compounds by supercritical fluid extraction and pressurised liquid extraction

Selective extraction is a great concern in the field of natural products. The interest is to apply specific conditions favouring the solubility of targeted secondary metabolites and avoiding the simultaneous extraction of unwanted ones. Different ways exist to reach selective extractions with suited conditions. These conditions can be determined from experimental studies through experimental design, but a full experimental design takes time, energy, and uses plant samples. Prediction from varied solubility models can also be applied allowing a better understanding of the final selected conditions and eventually less experiments. The aim of this work was to develop and use a chromatographic model to determine optimal extraction conditions without the need for numerous extraction experiments. This model would be applied on the selective extraction of the desired antioxidant compounds in rosemary leaves (rosmarinic and carnosic acids) vs chlorophyll pigments to limit the green colour in extracts. This model was achieved with Supercritical Fluid Chromatography (SFC) and then applied to Supercritical Fluid Extraction (SFE) and Pressurised Liquid Extraction (PLE) assays. SFC models predicted low solubility of chlorophylls for low (5%) and high (100%) percentage of solvent in carbon dioxide. Also, low solubility was predicted with acetonitrile solvent compared to methanol or ethanol. This was confirmed with different extractions performed using SFE with different percentages of solvent (5, 30, and 70%) and with the three solvents used in the SFC models (acetonitrile, methanol and ethanol). Also extractions using PLE were carried out using the same neat solvents in order to confirm the SFC models obtained for 100% of solvent. Globally, extractions validated the SFC models. Only some differences were observed between ethanol and methanol showing the complexity of plant extraction due to matrix effect. For all these extracts, the content of carnosic acid and rosmarinic acid was also monitored and selective extraction conditions of bioactive compounds could be determined.

Volatile Transference and Antimicrobial Activity of Cheeses Made with Ewes' Milk Fortified with Essential Oils

During the last decades, essential oils (EOs) have been proven to be a natural alternative to additives or pasteurization for the prevention of microbial spoilage in several food matrices. In this work, we tested the antimicrobial activity of EOs from Melissa officinalis, Ocimum basilicum, and Thymus vulgaris against three different microorganisms: Escherichia coli, Clostridium tyrobutyricum, and Penicillium verrucosum. Pressed ewes' cheese made from milk fortified with EOs (250 mg/kg) was used as a model. The carryover effect of each oil was studied by analyzing the volatile fraction of dairy samples along the cheese-making process using headspace stir bar sorptive extraction coupled to gas chromatography/mass spectrometry. Results showed that the EOs contained in T. vulgaris effectively reduced the counts of C. tyrobutyricum and inhibited completely the growth of P. verrucosum without affecting the natural flora present in the cheese. By contrast, the inhibitory effect of M. officinalis against lactic acid bacteria starter cultures rendered this oil unsuitable for this matrix.