Effect of Saccharomyces cerevisiae cells immobilisation on mead production

The Impact of Furfural on the Quality of Meads

Furfural is a naturally occurring compound in bee honey, classified as a fermentation inhibitor. The aim of this study was to ascertain the concentration of furfural in mead worts, prepared at room temperature (unsaturated) and heated to boiling for 10 to 70 min (saturated), with an extract of 25 to 45°Brix. Moreover, the impact of the furfural on the fermentation course of mead wort was assessed. For this purpose, fermentation tests were conducted using mead wort (30°Brix) to which furfural was added at concentrations ranging from 1 to 100 mg/L. HS-SPME-GC-TOF-MS analysis revealed that the furfural concentration in mead worts varied between 2.3 and 5.3 mg/L. In saturated worts, the concentration increased by 2.8 to 4.5 times. Acidification of mead wort prior to boiling led to further increase in furfural concentration. The greatest changes occurred in the least concentrated worts, having the lowest buffer capacity. The addition of furfural to the mead wort did not inhibit fermentation, and an increase in attenuation was observed in the samples containing 2 mg/L of furfural compared to the control. Throughout the fermentation most of the furfural was reduced to furfuryl alcohol.

A review of fermented bee products: Sources, nutritional values, and health benefits

Bee products have garnered considerable interest due to their abundant nutritional content and versatile biological activities. The utilization of bee products as fermentation materials has shown favorable potential for increasing nutrients, altering texture, and endorsing unique tastes. This review critically examines the existing literature on fermented bee products, with a specific emphasis on the impact of fermentation on their nutritional composition and potential health benefits. The raw materials, strains, conditions, and methodologies employed in the fermentation of bee products, as well as the utilization of bee products as fermentation raw materials/excipients, are reviewed. We also present a special focus on the nutritional composition and content of bioactive substances, such as polyphenols and volatile organic compounds, in fermented bee products. Additionally, the influence of fermentation on bee product ingredients and their health benefits is summarized. Fermented bee products substantially benefit human health, with superior antioxidant, anti-inflammatory, and anti-allergic properties compared to non-fermented bee products. Finally, this article discusses the types, strains, health benefits, production processes, and market prospects of fermented bee products, which are expected to become an important part of human food culture as functional food or nutritional supplements. The aforementioned findings highlight the remarkable nutritional value and bioactive properties exhibited by fermented bee products.

Aromatic and sensorial characterization of "Moscato pyments": an innovative beverage

Pyment is a type of mead that is produced from the alcoholic fermentation of a honey solution with the addition of grape juice. Due to the demand for new beverages, pyment can be a profitable alternative for both grape and honey producers. Therefore, this work aimed to characterize the aromatic and physicochemical composition of pyments. The pyments were prepared with addition of 10, 20 and 30% of Moscato juice, and compared with Moscato wine and traditional mead. The results showed an increase in the fermentation rates of Moscato-pyments, indicating that the addition of Moscato juice reverses the low fermentative vigor often reported in mead fermentations. Physicochemical parameters showed an increase in total acidity and a decrease in residual sugar and alcohol, depending on Moscato juice concentration. Moscato-pyments showed an intermediate concentration of volatile compounds between the traditional mead and Moscato wine, with a better balance between fruity, floral and buttery, manifesting characteristic aromas of wines made with Moscato grapes and simultaneously, exposing characteristic aromas of honey. The sensory analysis reveals a significant difference between mead, pyments and Moscato wine. In general, pyments were considered, by the panelists, as the most equilibrated with intermediary aroma intensity, floral, fruity and honey aromas, and good persistence in the mouth.

Effects of different yeast strains, nutrients and glutathione-rich inactivated yeast addition on the aroma characteristics of Catarratto wines

Catarratto is one of the most common non-aromatic white grape varieties cultivated in Sicily (Southern Italy). In order to improve the aromatic expression of Catarratto wines a trial was undertaken to investigate the effect of yeast strain, nutrition and reduced glutathione. Variables included two Saccharomyces cerevisiae strains, an oenological strain (GR1) and one isolated from honey by-products (SPF52), three different nutrition regimes (Stimula Sauvignon Blanc™ (SS), Stimula Chardonnay™ (SC) and classic nutrition practice), and a specific inactivated yeast rich in reduced glutathione to prevent oxidative processes [Glutastar™ (GIY)] ensuing in ten treatments (T1-T10). Microbiological and chemical parameters demonstrated the aptitude of strain SPF52 to successfully conduct alcoholic fermentation. During fermentation, the Saccharomyces yeast populations ranged from 7 to 8 logarithmic CFU/mL. All wines had a final ethanol content ranging between 12.91 and 13.85% (v/v). The dominance of the two starter strains over native yeast populations was higher than 97% as estimated by interdelta analysis. The addition of nutrients SS or SC increased the aromatic complexity of the wines as reflected by volatile organic compounds (VOCs) composition and sensory profiles. In particular, 32 VOCs were identified; alcohols (62.46-81.1%), thiols (0.27-0.87%), ethers (0.09-0.16%), aldehydes (0-1.21%), ketones (0-2.28%), carboxylic acids (4.21-12.32%), esters (0-10.85%), lactones (0.9-1.49%) and other compounds (0.77-6.9%). Sensory analysis demonstrated a significant impact on wine aroma in relation to yeast starter strain used, the type of nutrition (SS, SC or classic nutrition) and the presence/absence of GIY. The wines produced with GR1 yeast strain and SS (T2), SPF52 with SC (T9) both in presence of GIY showed higher overall quality. Trials T2 and T9 showed the highest scores for 13 and 18 attributes, respectively. The different nutrition, addition of GIY and the yeast starter strains diversified and enhanced sensory expression of Catarratto wines.

Impact of Fermentation Processes on the Bioactive Profile and Health-Promoting Properties of Bee Bread, Mead and Honey Vinegar

Recently, an increasing interest is paid to bee products obtained as a result of the fermentation process. Some of them can be consumed directly (bee-collected pollen, honey, bee bread etc.), while others are the result of lactic and/or acid fermentation (honey vinegar and honey wine). Bee bread is the result of pollens’ lactic fermentation, whereas mead is obtained by honeys’ lactic fermentation. Moreover, as a result of honey acetic acid fermentation, honey vinegar is obtained. Sensory characteristics and aroma composition have been scarcely studied, which may depend on the starter culture and fermentation process. Along with the medicinal properties they are a vital resource for future researches as they are of particular importance in the food market. In this review, we discuss the aroma-active compounds, taste, and sensorial characteristics of fermented bee products along with the approaches that can be developed for the flavor improvement based on existing technologies. Furthermore, the beneficial effects on human health are also described, with special attention that should be attributed to finding the use of probiotics in these fermented products as health-promoting effects.

Synthesis and characterization of mead: from the past to the future and development of a new fermentative route

In ancient times, mead was produced by fermentation of honey in water and presented low quality, undesired by-products, off-flavors, and the production was time consuming. In this study, nine experiments were performed to improve the fermentation and mead characteristics. Distillation was not part of the production process and it was performed in this work to produce a new spirit. The samples were characterized by gas chromatography coupled to mass spectrometry, high performance liquid chromatography, digital densimetry, titration, gravimetric method, pH, and refractometry. The results were compared to commercial beverages and legal limits. The meads presented high ethanol concentration, low by-products, fast fermentation, and high quality. The spirits showed high quality and the concentrations of acetic acid, ethyl acetate, methanol, higher alcohols, and ethyl carbamate were below the limits for safe consumption. In conclusion, it was possible to develop new conditions to produce high quality mead and mead spirit.

Volatile Composition and Sensory Properties of Mead

Mead is a traditional beverage that results from the alcoholic fermentation of diluted honey performed by yeasts. Although the process of mead production has been optimized in recent years, studies focused on its sensory properties are still scarce. Therefore, the aim of this work was to analyse the sensory attributes of mead produced with free or immobilized cells of the Saccharomyces cerevisiae strains QA23 and ICV D47, and to establish potential correlations with its volatile composition. In the volatile composition of mead, the effect of yeast condition was more important than the strain. In respect to sensory analysis, the most pleasant aroma descriptors were correlated with mead obtained with free yeast cells, independently of the strain. Both sensory analysis and volatile composition indicates that the most pleasant mead was produced by free yeast cells. Although this study has provided a significant contribution, further research on the sensory quality of mead is still needed.

Effect of different starter cultures on chemical and microbial parameters of buckwheat honey fermentation

The aim of this study was to analyze the microbiology of buckwheat honey fermentation inoculated with different starter cultures by culturing and PCR-DGGE, taking as a model for comparison a spontaneously fermented batch. The inoculants tested were (i) cider lees (from a cider factory), (ii) sourdough (from a bakery), and (iii) a commercial Saccharomyces cerevisiae strain. The results of the culturing and culture-independent techniques agreed well and detected the same dominant species along the fermentations. Our results suggest that S. cerevisiae strains, which constituted a majority population in all batches including the uninoculated one, carried out the fermentations. The highest microbial diversity was found at the beginning of the fermentation in the uninoculated batch; this contained in addition to S. cerevisiae bacteria (Paracoccus sp., Staphylococcus sp., and Bacillus sp.) and yeast (Candida sp.) species. Candida sp. was also common in batches inoculated with sourdough and cider lees cultures. Lactobacillus species were found throughout the fermentation of the sourdough-inoculated batch. Basic chemical analysis and testing trials demonstrated that the overall sensory acceptance of the four meads were highly similar. Yeast and bacteria isolated in this study could serve as a source of technologically relevant microorganisms for mead production.

Characteristics of Biologically Active Compounds in Cornelian Cherry Meads

In this study, we investigated the effect of Cornelian cherry cultivars differing in fruit color ("Yantaryi"-yellow fruits, "Koralovyi"-coral fruits, "Podolski"-red fruits) on physicochemical characteristics, antioxidative properties, and contents of iridoids and polyphenols in meads with the addition of juices made of their fruits. "Trójniak" type meads (1:2 honey to water volume) were manufactured from multifloral honey, to which Cornelian cherry fruit juice was added before fermentation. Concentrations of individual iridoids and polyphenols were determined using HPLC analysis with a thermostat refractometric detector, model RID-10A. The total polyphenol content was determined based on testing with Folin⁻Ciocalteu (F-C) reagent, whereas the antioxidative properties were determined using DPPH^• (2,2-Diphenyl-2-picryl-hydrazyl), ABTS^•⁺ (2,2'-Azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid), and FRAP (ferric reducing antioxidant power) assays. Cultivar of Cornelian cherry fruits influenced both the antioxidative properties and the concentrations of polyphenols and iridoids. The highest concentration of total polyphenols (F-C), accounting for 898.7 mg gallic acid (GAE)/L, was determined in the mead with juice made of red fruits; this mead was also characterized by the strongest antioxidative capabilities measured with ABTS^•⁺ and FRAP assays. Among the iridoids determined in the Cornelian cherry meads, loganic acid was found to prevail and its highest concentration, reaching 77.8 mg loganic acid (LA)/L mead, was determined in the mead with the coral-fruit juice. Study results indicate that Cornelian cherry meads have a high content of biologically active iridoids and phenolic acids which display valuable antioxidative properties.

Yeast Immobilization Systems for Alcoholic Wine Fermentations: Actual Trends and Future Perspectives

Yeast immobilization is defined as the physical confinement of intact cells to a region of space with conservation of biological activity. The use of these methodologies for alcoholic fermentation (AF) offers many advantages over the use of the conventional free yeast cell method and different immobilization systems have been proposed so far for different applications, like winemaking. The most studied methods for yeast immobilization include the use of natural supports (e.g., fruit pieces), organic supports (e.g., alginate), inorganic (e.g., porous ceramics), membrane systems, and multi-functional agents. Some advantages of the yeast-immobilization systems include: high cell densities, product yield improvement, lowered risk of microbial contamination, better control and reproducibility of the processes, as well as reuse of the immobilization system for batch fermentations and continuous fermentation technologies. However, these methods have some consequences on the behavior of the yeasts, affecting the final products of the fermentative metabolism. This review compiles current information about cell immobilizer requirements for winemaking purposes, the immobilization methods applied to the production of fermented beverages to date, and yeast physiological consequences of immobilization strategies. Finally, a recent inter-species immobilization methodology has been revised, where yeast cells are attached to the hyphae of a Generally Recognized As Safe fungus and remain adhered following loss of viability of the fungus. The bio-capsules formed with this method open new and promising strategies for alcoholic beverage production (wine and low ethanol content beverages).

Simultaneous Alcoholic and Malolactic Fermentations by Saccharomyces cerevisiae and Oenococcus oeni Cells Co-immobilized in Alginate Beads

Malolactic fermentation (MLF) usually takes place after the end of alcoholic fermentation (AF). However, the inoculation of lactic acid bacteria together with yeast starter cultures is a promising system to enhance the quality and safety of wine. In recent years, the use of immobilized cell systems has been investigated, with interesting results, for the production of different fermented foods and beverages. In this study we have carried out the simultaneous immobilization of Saccharomyces cerevisiae and Oenococcus oeni in alginate beads and used them in microvinifications tests to produce Negroamaro wine. The process was monitored by chemical and sensorial analyses and dominance of starters and cell leaking from beads were also checked. Co-immobilization of S. cerevisiae and O. oeni allowed to perform an efficient fermentation process, producing low volatile acidity levels and ethanol and glycerol concentrations comparable with those obtained by cell sequential inoculum and co-inoculum of yeast and bacteria cells in free form. More importantly, co-immobilization strategy produced a significant decrease of the time requested to complete AF and MLF. The immobilized cells could be efficiently reused for the wine fermentation at least three times without any apparent loss of cell metabolic activities. This integrated biocatalytic system is able to perform simultaneously AF and MLF, producing wines similar in organoleptic traits in comparison with wines fermented following traditional sequential AF and MLF with free cell starters. The immobilized-cell system, that we here describe for the first time in our knowledge, offers many advantages over conventional free cell fermentations, including: (i) elimination of non-productive cell growth phases; (ii) feasibility of continuous processing; (iii) re-use of the biocatalyst.

Developments in the fermentation process and quality improvement strategies for mead production

Mead is a traditional alcoholic drink derived from the fermentation of diluted honey in the presence of appropriate yeast. Its modern production, in general terms, involves the addition of nutrients to initial diluted honey, pasteurization, yeast inoculation, fermentation and removal of impurities. Undesirable events along the process have been reported; among them, we highlight: delayed or arrested fermentations, modified and unpleasant sensory and quality parameters of the final product. These problems have been linked to the inability of yeasts to accomplish their role in extreme growth conditions. Emphasis has also been placed on the long fermentation times required, ranging from weeks to months, particularly when traditional procedures are applied and when the honey concentration is low. A series of alterations to the must and technological changes have been proposed in order to optimize the mead production process. In this context, this review examines the evidence that aims to improve meads' quality and make the production process easier and more efficient, by clarifying the source of unexpected events, describing the implementation of different fermentative microorganisms and using new methodologies.