Bactericidal effect of ultraviolet-C treatments applied to honey

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.

Inactivation of Clostridium Spores in Honey with Supercritical CO2 and in Combination with Essential Oils

The presence of tens of Clostridium botulinum spores per gram of honey can cause infantile botulism. Thermal treatment is insufficient to inactivate these resistant forms. This study explored the effectiveness of supercritical CO2 (scCO2) on its own and combined with lemon (LEO), clove (CLEO), and cinnamon (CEO) essential oils on the inactivation of Clostridium sporogenes (CECT 553) as a surrogate of Clostridium botulinum. In water, the degree of inactivation at 10 MPa after 60 min increased with the increasing temperature, reducing the population by 90% at 40 °C and by 99.7% at 80 °C. In contrast, when applied to honey, scCO2 did not inactivate Clostridium spores satisfactorily at temperatures below 70 °C, which was related to the protective effect of honey. Meanwhile, scCO2 modified with CEO (<0.4% mass) improved the inactivation degree, with a 1.3-log reduction achieved at 60 °C. With this same mixture, a reduction of 3.7 logs was accomplished in a derivative with 70% moisture. Honey was very sensitive to the temperature of the applied CO2. The obtained product could be used as a novel food, food ingredient, cosmetic, or medicine.

The inhibitory effect of Ukrainian honey on probiotic bacteria

Honey is used in the food industry as a natural sweetener and has therapeutic effects on the human body. Obtaining quality honey involves using organic preventive and treatment agents in beekeeping. The most common of these agents are probiotic supplements. This research aimed to study honey’s interaction with an inhibitory effect on the growth of microorganisms from the probiotic supplement Immunobacterin-D under laboratory and experimental field conditions. At the first stage of the research, we assessed the effects of ten honey varieties (buckwheat, sunflower, meadow and forest plants, linden) on B. subtilis and B. licheniformis from the dry probiotic supplement. The honey-containing nutrient media had an inhibitory effect on the growth of B. subtilis colonies. After 24 hours of cultivation under aerobic conditions, the concentration of B. subtilis decreased, on average, from 5×1012 colony-forming units in 1 g to 3.2×104 and 2.1×105 CFU/g in samples with monofloral and polyfloral honey, respectively. These results emphasize the need for further research on the symbiotic role of microflora in the stability of the microbiota of the hive and bee colony ecosystem. The next stage of the study investigated the probiotic effect on bee colonies in the field. Observations were made on the sanitary conditions of the hives and the behaviour of bees at the Petrodolyna demo apiary. No differences were found at the macro hive-bee colony ecosystem level between control bee colonies (n = 5) and the experimental ones (n = 5) that had received carbohydrate feeding with added probiotics. This confirms the inhibitory effect of honey on the development of bacteria, which eliminates the risk of uncontrolled growth of B. subtilis and B. licheniformis strain colonies inside the hive and the bacteria getting into bee products. The probiotic had positive effects, increasing the live weight of worker bees by 9.15% by the end of the apiary season compared to the control. This can improve the viability of the bees during wintering. At the last stage of the research, the honey obtained from the experimental colonies was checked for the spores of B. subtilis and B. licheniformis using melissopalynology.

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.

Effect of packaging methods and storage conditions on quality characteristics of flour product naan

The quality characteristics of naan from flour products under various packaging methods stored at different temperatures (25, 4 and - 20 °C) for different time (0-49 days) were investigated. Packaging methods included ordinary plastic packaging (OPP), vacuum packaging (VP) and deoxygenation packaging (DP). Sensory value, acid value, moisture content and microbial count of naan during storage were evaluated. The results showed that the total demerit points of sensory of DP naan stored at 25 °C had considerably lower levels. The moisture content of naan in DP and VP at 25 °C during storage had not been affected, while in OPP increased; the acid values of naan increased, but in DP was the lowest; the total microbiological count (MC) of naan in OPP, VP and DP at 5th day reached 2.25, 3.04 and 1.99 log CFU g^-1, respectively. At 4 and - 20 °C, the moisture content of naan in OPP, VP and DP during storage reduced, the acid values at storage the 38th day dramatically increased (p < 0.05), the MC slowly increased, but these in DP samples was lower. The Ultraviolet (UV) and microwave (MW) radiation time was varied to study its effect on the shelf life of naan at 25 °C. The moisture content of UV and MW treated naan were not significantly different from those of control naan (p > 0.05), but the demerit points, acid values and MC reduced, the shelf life of naan was extended. The combination of DP and MW methods was a better efficient way to reduced negative quality changes of naan during storage.

Strategies of Phytophthora infestans adaptation to local UV radiation conditions

Expected global changes in environmental conditions underline the need for a better understanding of genetic variation in ecological traits and their strategies of adaptation to the stresses. In this study, evolutionary mechanisms and processes of UV adaptation in plant pathogens were investigated by combining statistical genetics, physiological assays, and common garden experiment approaches in an assessment of the potato late blight pathogen, Phytophthora infestans, sampled from various geographic locations in China. We found spatial divergence caused by diversifying selection in UV tolerance among P. infestans populations. Local UV radiation was the driving force of selection as indicated by a positive correlation between UV tolerance in P. infestans populations and the altitude of collection sites. Plasticity accounted for 68% of population variation while heritability was negligible, suggesting temporary changes in gene expression and/or enzymatic activity play a more important role than permanent modification of gene structure in the evolution of UV adaptation. This adaptation strategy may explain the lack of fitness penalty observed in genotypes with higher UV tolerance.