Antimicrobial activity of heat-treated Polish honeys

Radiofrequency affects the decrystallization efficiency and physicochemical properties of rape honey via crystal structure modification and inactivating enzyme

Crystallization degrades the physicochemical properties of honey and reduces consumer acceptance. To address this issue, radiofrequency was developed to investigate the decrystallization efficiency and quality impact mechanism of rape honey. The results showed that radiofrequency significantly decreased the number and size of crystals, leading to shortening the decrystallization time to less than 10 min. The response surface optimization methodology further indicated that the highest decrystallization rate (98.72 ± 0.34 %) and lower 5-Hydroxymethylfurfural (2.45 ± 0.12 mg/kg) contents were obtained. Furthermore, radiofrequency changed the honey from a pseudoplastic into a Newtonian fluid efficiently due to the volumetric heating feature. It is worth noting that the inactivation of glucose oxidase reduced the antibacterial capacity, while the increase in total phenolic and flavonoid contents improved the antioxidant capacity of rape honey. In summary, current findings indicated that radiofrequency is a potential alternative decrystallization technology for water baths.

Honey microbiota, methods for determining the microbiological composition and the antimicrobial effect of honey - A review

Honey is a natural product used since ancient times due to its taste, aroma, and therapeutic properties (antibacterial, antiviral, anti-inflammatory, and antioxidant activity). The purpose of this review is to present the species of microorganisms that can survive in honey and the effect they can have on bees and consumers. The techniques for identifying the microorganisms present in honey are also described in this study. Honey contains bacteria, yeasts, molds, and viruses, and some of them may present beneficial properties for humans. The antimicrobial effect of honey is due to its acidity and high viscosity, high sugar concentration, low water content, the presence of hydrogen peroxide and non-peroxidase components, particularly methylglyoxal (MGO), phenolic acids, flavonoids, proteins, peptides, and non-peroxidase glycopeptides. Honey has antibacterial action (it has effectiveness against bacteria, e.g. Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Acinetobacter, etc.), antifungal (effectiveness against Candida spp., Aspergillus spp., Fusarium spp., Rhizopus spp., and Penicillium spp.), antiviral (effectiveness against SARS-CoV-2, Herpes simplex virus type 1, Influenza virus A and B, Varicella zoster virus), and antiparasitic action (effectiveness against Plasmodium berghei, Giardia and Trichomonas, Toxoplasma gondii) demonstrated by numerous studies that are comprised and discussed in this review.

In vitro testing of honey quality and biological functionality: underestimated elements in the clinical testing of honey

Honey is an attractive functional food that often becomes a subject of clinical studies on the treatment of diverse diseases. However, the clinical efficacy of honey is rather controversial due, at least in part, to its variable composition and botanical origin as well as thermal processing or improper storage conditions. This review addresses the importance of honey quality standards and in vitro testing of the biological properties of honey prior to performing clinical studies, which can have a great impact on clinical outcomes. It focused on recently performed meta-analyses and systematic reviews where honey was used in the management of various disorders including respiratory tract infections, and metabolic and cardiometabolic diseases, with the goal of characterising the honeys used in clinical studies. In addition, it provides recommendations for the use and storage of honey for clinical testing. The vast majority of clinical studies included in meta-analyses do not provide any information about honey quality parameters. In fact, indicators of thermal damage or prolonged storage of honey were analysed only in one clinical study. This observation highlights on the alarming status of honey quality in clinical studies. Furthermore, in vitro biological properties of the analysed honeys were assessed in two clinical studies. Therefore, this review strongly advocates the clinical use of only fully characterised honey samples of known botanical origin with proven in vitro biological functionality and no or minimal thermal processing.

Fabrication and characterization of alginate-zein core-shell microcapsules for controlled release of buckwheat honey

In this study, extrusion method was employed to fabricate alginate-zein core-shell microcapsules loaded with buckwheat honey by dropping alginate and buckwheat honey mixture solution into a 70.0 % zein ethanol solution(v/v) containing 5.0 % CaCl2 solution (wt%). The microcapsules were constructed by two parts: 1) the formation of hydrophilic beads through the crosslinking of alginate chains with Ca2+; 2) the introduction of alginate beads into the aqueous zein ethanol solution which decreased the ethanol concentration, prompting the precipitation of zein and the deposition of zein nanoparticles onto the surfaces of alginate beads. Comparing with the alginate beads, the prepared microcapsules not only possessed better water-holding capacity, but also achieved controlled release of buckwheat honey. Importantly, the microcapsules significantly retained the antioxidant activity of the buckwheat honey. Therefore, this innovative method for fabricating alginate-zein core-shell microcapsules can suggest a promising approach to broaden the application of buckwheat honey in the food field.

Nutritional profiling, fiber content and in vitro bioactivities of wheat-based biscuits formulated with novel ingredients

This study evaluated the nutritional profile and fiber content of innovative formulations of wheat-based biscuits enriched with chia seeds, carob flour and coconut sugar. The in vitro antioxidant, cytotoxic, anti-inflammatory and antimicrobial activities were also investigated to understand the potential health advantages of the incorporation of these new ingredients. The novel biscuits demonstrated significant improvements in protein and mineral content, with increases of 50% and 100% in chia biscuits, and up to 20% and 40% in carob biscuits, respectively. Fiber also notably increased, particularly in samples containing 10% carob flour, which increased four times as compared to wheat-based samples. The new ingredients exhibited antibacterial and antifungal activity, particularly against Yersinia enterocolitica (minimum inhibitory concentration 1.25 mg mL-1 in coconut sugar) and Aspergillus fumigatus (minimum inhibitory concentration/minimum fungicidal concentrations 2.5/5 mg mL-1 in chia seeds). However, the final biscuits only displayed antifungal properties. Carob flour and chia seeds had a remarkably high capacity to inhibit the formation of TBARS and promoted greater antioxidant activity in biscuit formulations, with EC50 values decreasing from 23.25 mg mL-1 (control) to 4.54 mg mL-1 (15% defatted ground chia seeds) and 1.19 mg mL-1 (10% carob flour). Only chia seeds exhibited cellular antioxidant, anti-inflammatory and cytotoxic activity, attributes that were lost when seeds were added into the biscuits. These findings highlight the potential health benefits of these ingredients, particularly when incorporated in new wheat-based formulations.

Ultrasonication for honey processing and preservation: A brief overview

Honey is a food product consumed all over the world. Besides its nutritional properties, honey presents antibacterial, antioxidant, and wound-healing properties. To ensure that the final product meets qualitative and microbiological standards, honey treatment is of great importance. Conventional honey treatment is based on the heating of honey samples for decrystallization and bacteria and yeast inactivation. However, conventional heating can cause negative effects on honey quality, such as the formation of toxic compounds, reduction of enzyme activity, and loss of antioxidant and antimicrobial properties. The application of ultrasonic waves has demonstrated interesting effects on honey processing. Ultrasound (US) treatment can lead to the fragmentation of glucose crystals in crystalized honey and has little effect on its properties. In addition to inactivating microorganisms, US-assisted honey processing also preserves phenolic compounds content and antimicrobial properties. However, there is still limited information about honey sonication. The aim of the present review is to comprehensively show the possibilities of US application in honey processing and its effects on honey properties.

Changes in antibacterial activity, colour, and hydrogen peroxide content of Western Australian Jarrah and Marri honeys after storage at different temperatures over time

AIMS

This study aimed to evaluate the effects of storage and different temperatures on the antibacterial activity and physicochemical characteristics of several types of honey.

METHODS AND RESULTS

Honeys stored for 16 weeks at 37 and 45°C showed significant declines in antibacterial activity determined by minimum inhibitory concentrations, the loss of hydrogen peroxide, decreases in honey pH, and increases in honey colour, with changes most pronounced at 45°C. In contrast, honeys stored for 16 weeks at ambient (∼22°C) and cold (4, -20, and -80°C) temperatures showed only minor changes. In a second set of 12 honeys stored for 16-32 months at ambient temperature and then 4°C, honeys showed minor changes in antibacterial activity, increases in colour, and decreases in pH. For a third set of 17 honeys stored for five years at ambient temperature, the honeys showed almost complete loss of hydrogen peroxide and were all significantly darker in colour, but showed varied changes in antibacterial activity.

CONCLUSIONS

Heat was detrimental to the antibacterial activity of honeys, as was long-term storage at ambient temperatures for some honeys but not others.

High-Pressure-Based Strategies for the Inactivation of Bacillus subtilis Endospores in Honey

Honey is a value-added product rich in several types of phenolic compounds, enzymes, and sugars recently explored in biomedical and food applications. Nevertheless, even though it has a low water activity (a_W ≈ 0.65) that hinders the development of pathogenic and spoilage microorganisms, it is still prone to contamination by pathogenic microorganisms (vegetative and spores) and may constitute harm to special groups, particularly by immunosuppressed people and pregnant women. Thus, an efficient processing methodology needs to be followed to ensure microbial safety while avoiding 5-hydroxymethylfurfural (HMF) formation and browning reactions, with a consequent loss of biological value. In this paper, both thermal (pressure-assisted thermal processing, PATP) and nonthermal high-pressure processing (HPP), and another pressure-based methodology (hyperbaric storage, HS) were used to ascertain their potential to inactivate Bacillus subtilis endospores in honey and to study the influence of a_W on the inactivation on this endospore. The results showed that PATP at 600 MPa/15 min/75 °C of diluted honey (52.9 °Brix) with increased a_W (0.85 compared to ≈0.55, the usual honey a_W) allowed for inactivating of at least 4.0 log units of B. subtilis spores (to below detection limits), while HS and HPP caused neither the germination nor inactivated spores (i.e., there was neither a loss of endospore resistance after heat shock nor endospore inactivation as a consequence of the storage methodology). PATP of undiluted honey even at harsh processing conditions (600 MPa/15 min/85 °C) did not impact the spore load. The results for diluted honey open the possibility of its decontamination by spores’ inactivation for medical and pharmaceutical applications.

Physicochemical Characterization and Biological Properties of Pine Honey Produced across Greece

Pine honey is a honeydew honey produced in the East Mediterranean region (Greece and Turkey) from the secretions of the plant sucking insect Marchalina hellenica (Gennadius) (Coccoidea: Marchalini-dae) feeding on living parts of Pinus species. Nowadays, honeydew honey has attracted great attention due to its biological activities. The aim of this study was to study unifloral pine honey samples produced in Greece regarding their physicochemical parameters and antioxidant and antibacterial activity against five nosocomial and foodborne pathogens. These honeys showed physicochemical and microscopic characteristics within the legal limits, except for diastase activity, a parameter known to be highly variable, depending on various factors. Substantially higher levels of H2O2 were estimated compared to other types of honeydew honey, whereas protein content was similar. The total phenolic content was 451.38 ± 120.38 mg GAE/kg and antiradical activity ranged from 42.43 to 79.33%, while FRAP values (1.87 to 9.43 mmol Fe+2/kg) were in general higher than those reported in the literature. Various correlations could be identified among these parameters. This is the first attempt to investigate in depth the antibacterial activity of pine honey from Greece and correlate it with honey quality parameters. All tested honeys exerted variable but significant antibacterial activity, expressed as MIC and MBC values, comparable or even superior to manuka honey for some tested samples. Although honey antibacterial activity is mainly attributed to hydrogen peroxide and proteins in some cases (demonstrated by elevated MICs after catalase and Proteinase K treatment, respectively), no strong correlation between the antibacterial activity and hydrogen peroxide concentration or total protein content was demonstrated in this study. However, there was a statistically significant correlation of moisture, antioxidant and antibacterial activity against Klebsiella pneuomoniae, as well as antioxidant and antibacterial activity against Salmonella ser. Typhimurium. Interestingly, a statistically significant negative correlation has been observed between diastase activity and Staphylococcus aureus antibacterial activity. Overall, our data indicate multiple mechanisms of antibacterial activity exerted by pine honey.

Effect of Temperatures on Polyphenols during Extraction

Background: Polyphenols are a set of bioactive compounds commonly found in plants. These compounds are of great interest, as they have shown high antioxidant power and are correlated to many health benefits. Hence, traditional methods of extraction such as solvent extraction, Soxhlet extraction and novel extraction technologies such as ultrasound-assisted extraction and subcritical water extraction (SWE) have been investigated for the extraction of polyphenols. Scope and Approach: Generally, for traditional extractions, the total phenolic content (TPC) is highest at an extraction temperature of 60–80 °C. For this reason, polyphenols are regularly regarded as heat-labile compounds. However, in many studies that investigated the optimal temperature for subcritical water extraction (SWE), temperatures as high as 100–200 °C have been reported. These SWE extractions showed extremely high yields and antioxidant capacities at these temperatures. This paper aimed to examine the relevant literature to identify and understand the mechanisms behind this discrepancy. Results: Thermal degradation is the most common explanation for the degradation of polyphenols. This may be the case for specific or sub-groups of phenolic acids. The different extraction temperatures may have also impacted the types of polyphenols extracted. At high extraction temperatures, the formation of new compounds known as Maillard reaction products may also influence the extracted polyphenols. The selection of source material for extraction, i.e., the plant matrix, and the effect of extraction conditions, i.e., oxidation and light exposure, are also discussed. The overestimation of total phenolic content by the Folin–Ciocâlteu assay is also discussed. There is also a lack of consensus in TPC’s correlation to antioxidant activity.

Conventional and emergent technologies for honey processing: A perspective on microbiological safety, bioactivity, and quality

Honey is a natural food of worldwide economic importance. Over the last decades, its potential for food, medical, cosmetical, and biotechnological applications has been widely explored. One of the major safety issues regarding such applications is its susceptibility to being contaminated with bacterial and fungi spores, including pathogenic ones, which may impose a hurdle to its consumption in a raw state. Another factor that makes this product particularly challenging relies on its high sugar content, which will lead to the formation of hydroxymethylfurfural (HMF) when heated (due to Maillard reactions). Moreover, honey's bioactivity is known to be affected when it goes through thermal processing due to its unstable and thermolabile components. Therefore, proper food processing methodologies are of utmost importance not only to ensure honey safety but also to provide a high-quality product with low content of HMF and preserved biological properties. As so, emerging food processing technologies have been employed to improve the safety and quality of raw honey, allowing, for example, to reduce/avoid the exposure time to high processing temperatures, with consequent impact on the formation of HMF. This review aims to gather the literature available regarding the use of conventional and emergent food processing technologies (both thermal and nonthermal food processing technologies) for honey decontamination, preservation/enhancement of honey biological activity, as well as the sensorial attributes.

In Vitro Antibacterial and Antibiofilm Activity of Hungarian Honeys against Respiratory Tract Bacteria

Honey is a rich source of carbohydrates, while minor compounds such as amino acids and polyphenols contribute to its health-promoting effects. Honey is one of the oldest traditional remedies applied for microbial infections, due to its antibacterial, anti-inflammatory, and antioxidant properties. The aim of this study was to investigate the antibacterial and antibiofilm effects of Hungarian black locust, linden, and sunflower honeys against the most common biofilm-forming respiratory tract pathogens Haemophilus spp., Pseudomonas aeruginosa, and Streptococcus pneumoniae. The unifloral character of all three honey types was confirmed by melissopalynological analysis. The antibacterial activity of each honey sample against each bacterium strain was proven with agar well diffusion assay and thin layer chromatography—direct bioautography. Kinetics and mechanisms of antibacterial action were clarified with time-kill assay and membrane degradation study. The anti-biofilm activity was evidenced using crystal violet assay. In each assay, linden honey was the most effective, followed by sunflower and black locust honey. In addition, each honey sample had greater potential to suppress respiratory tract bacteria, compared to major sugar components. In conclusion, honey in general and linden honey in particular, can have a role in the treatment of respiratory tract infections caused by biofilm-forming bacteria.

Effect of thermal liquefaction on quality, chemical composition and antibiofilm activity against multiresistant human pathogens of crystallized eucalyptus honey

Thermal liquefaction is a conventional method used by beekeepers to liquefy crystallized honey. However, an abusive use of heat may affect its quality, chemical composition and bioactivity. The purpose of this study was to investigate the effect of thermal liquefaction on the quality, chemical composition and antibiofilm properties of eucalyptus honey. Thermal liquefaction (at 45 and 60 °C) did not affect the honey's quality; however, a significant reduction in the reducing capacity, total phenolic content and hydrogen peroxide content was observed. At 60 °C, a significant reduction in the honey's ability to inhibit biofilm formation was observed in Pseudomonas aeruginosa, as well as a reduction in its ability to remove preformed biofilms in both Staphylococcus aureus and Pseudomonas aeruginosa. Structural changes in biofilm architecture caused by honey were not affected by thermal treatment. Therefore, we recommend liquefaction at 45 °C as the most convenient for honey liquefaction without affecting its characteristics.

Promising Antimicrobial Properties of Bioactive Compounds from Different Honeybee Products

Bee products have been known for centuries for their versatile healing properties. In recent decades they have become the subject of documented scientific research. This review aims to present and compare the impact of bee products and their components as antimicrobial agents. Honey, propolis, royal jelly and bee venom are bee products that have antibacterial properties. Sensitivity of bacteria to these products varies considerably between products and varieties of the same product depending on their origin. According to the type of bee product, different degrees of activity were observed against Gram-positive and Gram-negative bacteria, yeasts, molds and dermatophytes, as well as biofilm-forming microorganisms. Pseudomonas aeruginosa turned out to be the most resistant to bee products. An analysis of average minimum inhibitory concentration values for bee products showed that bee venom has the strongest bacterial effectiveness, while royal jelly showed the weakest antibacterial activity. The most challenging problems associated with using bee products for medical purposes are dosage and safety. The complexity and variability in composition of these products raise the need for their standardization before safe and predictable clinical uses can be achieved.

Chrysin: Perspectives on Contemporary Status and Future Possibilities as Pro-Health Agent

Chrysin belongs to the group of natural polyphenols. It can be found, among others, in honey, propolis and fruits and has a wide range of biological activities, including the prevention of oxidative stress, inflammation, neurodegeneration and carcinogenesis. Being a part of the human diet, chrysin is considered to be a promising compound to be used in the prevention of many diseases, including cancers, diabetes and neurodegenerative diseases such as Alzheimer's or Parkinson's. Nevertheless, due to the low solubility of chrysin in water and under physiological conditions, its bioavailability is low. For this reason, attempts at its functionalization have been undertaken, aiming to increase its absorption and thus augment its in vivo therapeutic efficacy. The aim of this review is to summarize the most recent research on chrysin, including its sources, metabolism, pro-health effects and the effects of its functionalization on biological activity and pharmacological efficacy, evaluated both in vitro and in vivo.