Mead production: effect of nitrogen supplementation on growth,fermentation profile and aroma formation by yeasts in mead fermentation

Mead is an alcoholic beverage, produced since ancient times, resulting from an alcoholic fermentation of diluted honey by yeasts. When it is produced in a traditional manner, mead producers can encounter several problems related to a lack of essential nutrients, such as available nitrogen. Thus, the aim of this study was to evaluate the effect of nitrogen addition to honey‐must on the fermentation performance of two Saccharomyces cerevisiae wine yeasts, QA23 and ICV D47, as well as on the mead composition and production of volatile aroma compounds. A portion of honey‐must was supplemented with diammonium phosphate (DAP) to achieve the nitrogen concentration required by yeast to complete alcoholic fermentation. The supplementation with DAP reduced the fermentation length to around 7 days, but not all sugars were fully consumed, suggesting that other factors could be interfering with yeast growth. For both yeasts the specific growth rate and final biomass were higher in musts supplemented with DAP. Mead final composition was similar under the two experimental conditions. Analysis of the volatile profile revealed that the concentrations of the volatile fatty acids and volatile phenols were higher in meads supplemented with DAP. The concentrations of ethyl hexanoate, ethyl octanoate and isoamyl acetate were above their perception threshold and were higher in meads supplemented with DAP, which could contribute to the enhancement of the fruity character. This study could be useful for the optimization of mead production and quality improvement. Copyright © 2015 The Institute of Brewing & Distilling     

Influence of pollen addition on mead elaboration: Physicochemical and sensory characteristics

Mead (honey-wine) results from the alcoholic fermentation of diluted honey using a wine yeast strain. However, mead elaboration can be hampered by several problems, including delayed or arrested fermentation, production of an unpleasant aroma, poor quality and inconsistency of the final product. These difficulties are due to honey’s low nutrient content, its natural antifungal components, and the inability of the yeast strain to adapt to these unfavourable growth conditions. In this study, we evaluated the results of adding pollen at concentrations ranging from 10 to 50 g/l as a fermentation activator to improve the fermentation kinetic and the quality of meads. The effect of pollen addition on the honey must, fermentation kinetics, physicochemical characteristics, aroma profiles and sensorial aspects of the obtained meads were evaluated. The results showed that pollen addition improved fermentation rates, alcohol yields, and the final characteristics of meads. An increase in the volatile contents of the meads and an improved sensory profile was observed with pollen addition; however, this improvement was not correlated with the concentration of pollen. The adequate dose of pollen was determined by the final characteristics and sensory profile of the meads.     

Effect of Saccharomyces cerevisiae cells immobilisation on mead production

Mead is a traditional alcoholic beverage obtained by the fermentation of diluted honey performed by yeasts. In this work the potential of application of immobilised yeast cells on single-layer Ca-alginate or double-layer alginate–chitosan for mead production was assessed for the first time. The meads produced either with entrapped or free cells were evaluated in terms of quality and aroma profile. The immobilisation procedure had no adverse effect on cell viability, since minor differences were found in fermentation kinetics among the strains and immobilisation systems. The double-layer alginate-chitosan had no advantage compared with the single-layer Ca-alginate, as the number of free cells in the medium, resulting from cell leakage, was similar. Although meads obtained with entrapped yeast cells presented less ethanol and glycerol and more acetic acid, it exhibited larger amounts of volatile compounds. Immobilised cells produced meads with more compounds with fruity characteristics, such as ethyl octanoate and ethyl hexanoate; however the concentrations of undesirable compounds in such meads were also higher. The effect of immobilisation on the aroma profile was important, but the strain contribution was also of major importance. Thus, the sensory analysis of final product gives an important insight on the overall quality.     

Optimization of honey-must preparation and alcoholic fermentation by Saccharomyces cerevisiae for mead production

Mead fermentation is a time-consuming process, often taking several months to complete. Despite of the use of starter cultures several problems still persist such as lack of uniformity of the final products, slow or premature fermentation arrest and the production of off-flavors by yeast. Thus the aim of this study was to optimize mead production through the use of an appropriate honey-must formulation to improve yeast performance alcoholic fermentation and thereby obtain a high quality product. Honey-must was centrifuged to reduce insoluble solids, pasteurized at 65 °C for 10 min, and then subjected to different conditions: nitrogen supplementation and addition of organic acids. Although the addition of diammonium phosphate (DAP) reduced fermentation length, it did not guarantee the completeness of the fermentation process, suggesting that other factors could account for the reduced yeast activity in honey-must fermentations. Sixteen yeast-derived aroma compounds which contribute to the sensorial quality of mead were identified and quantified. Global analysis of aromatic profiles revealed that the total concentration of aroma compounds in meads was higher in those fermentations where DAP was added. A positive correlation between nitrogen availability and the levels of ethyl and acetate esters, associated to the fruity character of fermented beverages, was observed whereas the presence of potassium tartrate and malic acid decreased, in general, their concentration.This study provides very useful information that can be used for improving mead quality.     

Physicochemical property changes during the fermentation of longan (Dimocarpus longan) mead and its aroma composition using multiple yeast inoculations

Mead is a traditional drink obtained from diluted honey with the appropriate yeast inoculations. However, the production of mead is time‐consuming, and the process often takes several months to accomplish. During the elaboration of mead, sluggish and stuck fermentations often occur and lead to the production of undesirable flavours. To improve the condition of longan mead production in Taiwan, multiple yeast inoculations with different strains of yeast were examined in this study. The physicochemical properties and mead aroma compounds were measured. Longan mead without multiple inoculations, but with added yeast nutrients, displayed a sharp increase in ethanol content compared with the inoculated groups without yeast nutrients. However, the physicochemical properties of every mead reached almost the same endpoint at the end of the fermentation time (day 22). Moreover, differences among the groups were observed in their aroma compounds. Some aroma compounds, such as 2‐methyltetrahydrothiophen‐3‐one, 1‐propanol and 2‐methylbutyl acetate, were only found in the double‐inoculation groups, whereas other aroma compounds, such as phenethyl acetate and linalool, were only found in the single‐yeast inoculation groups. These results demonstrate that multiple inoculations have a positive effect on longan mead fermentation. This technique could assist local producers in elaborating a longan mead of acceptable quality. Copyright © 2013 The Institute of Brewing & Distilling     

Mead production: fermentative performance of yeasts entrapped in different concentrations of alginate

Mead is an alcoholic drink known since ancient times, produced by yeast fermenting diluted honey. However, the production of mead has suffered in recent years, partially owing to the lack of scientific progress in this field. In this study, two strains of Saccharomyces cerevisiae, QA23 and ICVD47, were immobilized in 2 or 4% (w/v) alginate beads to assess the most effective alginate concentration for yeast immobilization to produce mead. Neither of the alginate concentrations was able to prevent cell leakage from the beads. The fermentation length was 120 h for both yeast strains. In all cases, at the end of the fermentation, the number of cells entrapped in the beads was higher than the number of free cells, and the total 4% alginate bead wet weight was significantly higher than the 2% alginate bead wet weight. In addition, the evaluation of mead quality showed that the yeast strain had significantly more influence on the physicochemical characteristics than the alginate concentration. Although the yeasts immobilized in the two alginate concentrations were able to perform the fermentation, further research is needed in order to understand the evolution of the yeast population inside the beads throughout the fermentative process. Copyright © 2014 The Institute of Brewing & Distilling     

响应面法优化五味子蜂蜜酒发酵工艺

以五味子和蜂蜜为主要原料制备五味子蜂蜜酒,以感官评分为评价指标,采用单因素试验及响应面试验对其发酵工艺条件进行优化,并对五味子蜂蜜酒的挥发性风味成分及理化指标进行测定。结果表明,五味子蜂蜜酒的最佳发酵工艺条件为：五味子含量1.9%、初始可溶性固形物含量25%、酵母接种量0.16%、初始p H值4.0。在此优化工艺条件下,五味子蜂蜜酒的感官评分为84.2分,酒精度为11.2%vol,总糖、总酸、可溶性固形物、木脂素、总多糖含量分别为24.6 g/L、6.1 g/L、8.8%、0.062 g/100 g、0.047 g/100 g。五味子蜂蜜酒中共检出挥发性香气成分17种,其中,酯类6种,醇类7种,烯类3种,醚类1种,主要的香气物质为乙醇、苯丙醇、2-甲基丁醇、D-柠檬烯和己酸乙酯。五味子蜂蜜酒呈琥珀色,具有浓郁果香与酒香。     

Increased flavour diversity of Chardonnay wines by spontaneous fermentation and co-fermentation with Hanseniaspora vineae

Discovery, characterisation and use of novel yeast strains for winemaking is increasingly regarded as a way for improving quality and to provide variation, including subtle characteristic differences in fine wines. The objective of this work was to evaluate the use of a native apiculate strain, selected from grapes, Hanseniaspora vineae (H. vineae) 02/5A. Fermentations were done in triplicate, working with 225 L oak barrels, using a Chardonnay grape must. Three yeast fermentation strategies were compared: conventional inoculation with a commercial Saccharomyces cerevisiae strain, ALG 804, sequential inoculation with H. vineae and then strain ALG 804 and spontaneous fermentation. Yeast strain identification was performed during fermentation, in which the apiculate strain was found to be active, until 9% of alcohol in volume, for the co-fermentation and the spontaneous fermentation was completed by three native S. cerevisiae strains. Basic winemaking parameters and some key chemical analysis, such as concentration of glycerol, biogenic amines, organic acids, and aroma compounds were analysed. Sensory analysis was done using a trained panel and further evaluated with professional winemakers. Sequential inoculation with H. vineae followed by S. cerevisiae resulted in relatively dry wines, with increased aroma and flavour diversity compared with wines resulting from inoculation with S. cerevisiae alone. Wines produced from sequential inoculations were considered, by a winemaker’s panel, to have an increased palate length and body. Characteristics of wines derived from sequential inoculation could be explained due to significant increases in glycerol and acetyl and ethyl ester flavour compounds and relative decreases in alcohols and fatty acids. Aroma sensory analysis of wine character and flavour, attributed to winemaking using H. vineae, indicated a significant increase in fruit intensity described as banana, pear, apple, citric fruits and guava. GC analysis of the relative accumulation of 23 compounds to significantly different concentrations for the three fermentation strategies is discussed in relation to aroma compound composition.     

Volatile aroma and sensory analysis of black raspberry wines fermented by different yeast strains

Robus coreanus Miquel is a small berry fruit used for Korean black raspberry (KBR) wine‐making. Twelve different yeast strains were investigated by laboratory‐scale fermentation to develop a wine with a high flavour quality. Volatile aroma compounds from the wines were analysed using headspace–solid phase microextraction–gas chromatography–mass spectrometry and sensory evaluation was performed to evaluate the flavour characteristics. The volatile aroma compounds that mostly contributed to the flavour of KBR wines were those related to fruity (esters) and floral (terpenes) aromas. Fifteen out of the 67 identified volatile compounds showed higher odour activity values than other compounds in the wines, and these compounds were considered as important contributors to the final aromas of the wine. Additionally, the KBR wine fermented by the M1 yeast strain had the highest sensory preference because of higher fruity and floral aroma characters compared with other wines. In addition to the M1 strain, the other yeast strains that produced favourable sensory characteristics included Enoferm CSM, Uvaferm VRB, Lalvin ICV GRE, Lalvin ICV Opale and LevureSeche Active. Of these strains, the M1 strain produced a particularly excellent black raspberry wine, and thus could be applied for further large‐scale production of black raspberry wines. It is also expected that this work will expedite research on the production of high‐quality black raspberry wines with beneficial physicochemical properties, functionality and good sensory characteristics. Copyright © 2015 The Institute of Brewing & Distilling     

Improvement of mead fermentation by honey‐must supplementation

Through honey's fermentation, diverse beverages can be obtained, among which is mead, an alcoholic drink with 8 to 18% of ethanol (v/v). Since honey is a matrix with a low nutrient concentration and other unfavourable growth conditions, several problems are usually encountered, namely delayed or arrested fermentations, unsatisfactory quality parameters and lack of uniformity of the final product, as well as unpleasant sensory properties. In this context, the aim of this work was to optimize mead production through honey‐must supplementation with (a) salts, (b) vitamins or (c) salts + vitamins. The effects of the honey‐must formulation on the fermentation kinetics, growth profile and physicochemical characteristics of final meads were evaluated. The results showed minor differences in the fermentation profile and time between fermentations with the different formulations. The growth profile was influenced more by the yeast strain than by the supplements added to the honey‐must. In general, the honey‐must composition did not influence meads’ final characteristics, except regarding the SO₂ concentration of the meads produced using the strain QA23. In summary, the addition of salts and/or vitamins to honey‐must had no positive effects on the fermentation, growth profile or characteristics of the final products. Copyright © 2015 The Institute of Brewing & Distilling     

The Effect of Pitching Rate on Fermentation and Flavour Compounds in High Gravity Brewing

The effect of pitching rate on fermentation and production of flavour compounds was studied in high gravity wort using a lager yeast. Fermentation performance was followed by monitoring the total sugar content and yeast growth. Volatile compounds were evaluated by analysing higher alcohols, esters and carbonyl compounds at the end of fermentation. Faster fermentation rates and higher yeast counts were observed with the higher pitching levels. Lower amounts of 2‐ and 3‐methyl‐1‐butanols and higher levels of 2‐methyl‐1‐propanol were found at the increased pitching rates. The concentration of isoamyl acetate was reduced with an increased pitching rate. Higher amounts of diacetyl and 2,3‐pentanedione were obtained at the lower pitching levels.     

Production of alcohol‐free beer with elevated amounts of flavouring compounds using lager yeast mutants

Arrested or limited fermentation process is a widespread method used for production of alcohol‐free beer (AFB). However, it usually leads to worty off‐flavour and a lack of pleasant fruity flavour/aroma. The aim of this study was to isolate spontaneous mutants of Saccharomyces pastorianus strain 2 resistant to 5,5,5‐trifluoro‐dl ‐leucine, since the resistance is related to overproduction of flavour active isoamyl alcohol (IAAL) and isoamyl acetate (IAAC). The mutants were the subject of selection during series of screening tests aimed at selecting the best producer of target compounds (IAAL and IAAC). Subsequently, the overproduction stability of the selected mutant strain was verified in four consecutive fermentations of AFBs. A higher pitching rate and increased fermentation temperature did not result in an overall improvement in the production of the target compounds. Sensory analysis proved the flavouring effect of the spontaneous lager yeast mutant on the AFB produced by arrested fermentation. Copyright © 2013 The Institute of Brewing & Distilling     

三华李果酒发酵工艺的优化及香气成分分析

以三华李为原料,进行三华李果酒主发酵工艺条件优化并分析鉴定果酒中的香气成分。通过比较不同品牌酵母产酒精能力的大小选择马利干酵母作为三华李果酒主发酵的发酵菌。研究了不同的酵母菌接种量、初始糖度、初始pH值、发酵温度对三华李果酒酒精度（酒精体积分数）的影响;在单因素试验的基础上进行了四因素三水平三华李果酒主发酵工艺条件的响应面优化。结果表明,三华李果酒主发酵的最佳工艺条件为：接种量5%、初始糖度24 °Bx、初始pH 3.70、发酵温度28 ℃、发酵时间5 d,在此条件下得到的酒精度为12.4%。该果酒经22 d后发酵,采用顶空固相微萃取法,利用气相色谱-质谱联用技术对其香气成分进行分析与鉴定,结果表明：从三华李果酒中共鉴定出31 种香气成分,占总峰面积的99.48%;其香气物质主要是异戊醇、异丁醇、乙酸乙酯和辛酸乙酯。     

The Influence of Inoculum Level on Fermentation and Flavour Compounds of White Wines Made from cv. Emir

In this study, the influence of the addition of a commercial wine yeast (Saccharomyces cerevisiae) at inocula of 1 × 10⁴ to 1 × 10⁷ cells/ml in Emir must was investigated with a focus on yeast growth, fermentation rate, ethyl alcohol and flavour compound formation. Spontaneous fermentation without inoculation was also performed. Higher peak counts were observed with higher amounts of S. cerevisiae yeast. Addition of various amounts of yeast led to the earlier disappearance of non‐Saccharomyces yeasts. The fermentation rate was improved with higher amounts of yeast, but ethanol production was not affected. Concentrations of higher alcohols increased with increasing inoculum levels, especially inoculum sizes of 1 × 10⁶ cells/ml and 1 × 10⁷ cells/ml. The amount of ethyl acetate was reduced with increased inoculum levels.     

共同定化多菌种发酵椪柑果醋工艺研究

以海藻酸钠为固定化材料,研究了多菌种（酿酒酵母、产香酵母、乳酸茵、醋酸菌）共固定化技术在椪柑果醋发酵中的应用。结果表明,固定化多菌种发酵椪柑果醋的最佳工艺条件为：酒精发酵阶段,接种量20％（v／v）、发酵温度32℃、时间60h、底物糖度23％;醋酸发酵阶段,接种量20％、发酵温度35℃、时间7d。所酿造的果醋具有椪柑的固有色泽、香气,无沉淀物,酸味柔和适中。     

草莓果酒酿造工艺的优化及其香气成分分析

以草莓为原料,采用单因素试验和Box-Behnken试验设计研究SO2添加量、酵母添加量及发酵温度对果酒发酵的影响,建立各影响因素的回归方程,并通过响应面分析法优化,得到草莓果酒的最佳工艺条件：SO2添加量为81 mg/L、酵母添加量为1 g/L、发酵温度为20 ℃。然后采用顶空固相微萃取法,利用气相色谱-质谱联用技术对草莓果酒香气成分进行分析与鉴定,结果表明：从草莓果酒中共鉴定出香气物质85 种,占总峰面积的99.55%;其主体香气物质主要是异戊醇、乙酸异戊酯、己酸乙酯及辛酸乙酯。     

Effect of fusel oil addition on volatile compounds in papaya wine fermented with Williopsis saturnus var. mrakii NCYC 2251

The impact of fusel oil addition on volatile compounds formation in papaya wine fermented with yeast Williopsis saturnus var. mrakii NCYC2251 was studied with a view to enhancing papaya wine aroma production. Time-course papaya juice fermentations were carried out using W. saturnus var. mrakii NCYC2251 with fusel oil added (0, 0.1 and 0.5% v/v). Fermentation characteristics in terms of yeast growth, Brix and pH changes were similar for all fermentations except for those added with 0.5% (v/v) fusel oil. The addition of 0.5% (v/v) fusel oil inhibited yeast growth. A wide range of volatile compounds were produced during fermentation including acids, alcohols, esters and aldehydes with esters being the most abundant volatile compounds produced. The addition of 0.1% (v/v) fusel oil reduced the production of undesirable volatiles such as ethyl acetate and acetic acid, while increasing the desirable volatiles production such as ethanol and acetate esters. This study suggests that papaya juice fermentation with W. saturnus var mrakii NCYC 2251 together with a low concentration of added fusel oil can be another means of modulating papaya wine aroma compound formation.     

Effect of oxygen and lipid supplementation on the volatile composition of chemically defined medium and Chardonnay wine fermented with Saccharomyces cerevisiae

Oxygen or lipids are required to complete stressful alcoholic fermentation. Lack of these nutrients can inhibit sugar uptake and growth, which leads to incomplete or ‘stuck’ fermentation. Oxygen or lipids supplementation not only restores yeast fermentative activity and also affects formation of yeast volatile metabolites. To clarify the effect of oxygen and lipid supplementation on the formation of flavour active metabolites during wine fermentation, we evaluated the addition of these two nutrients to chemically defined grape juice and filter clarified Chardonnay must. Lipid addition increased the concentration of esters, higher alcohols and volatile acids, whereas oxygen increased the concentration of higher alcohols and altered the proportion of acetate to ethyl esters and the proportion of branch-chain acids to medium-chain fatty acids. Combined addition of lipids and oxygen showed an additive effect on concentration of higher alcohols whereas oxygen suppressed the enhancing effect of lipids on formation of esters and volatile acids. Our results demonstrate the potential of lipid and oxygen supplementation for the manipulation of wine aroma in white wine fermentation.     

固态发酵用耐高温酿酒酵母YH_4的筛选及其特性研究

Saccharomyces cere(?)isiae YH(?)是从洋河酒厂处于顶火期的酒醅中分离出来的耐高温酵母,最适生长温度为35～38℃,最高生长温度为47℃。最适生长PH为4～6,对黄水中复合有机酸有较强的耐性。酒精发酵能力中等,发酵速度较慢。在实验室模拟固态发酵条件下,当对酒醅的接种量在2％以下时,将会使酒精产量明显增加,而且酒中的己酸乙酯含量不受显著影响,因此,该菌株在克服或减轻浓香型白酒夏季生产“掉排”现象中较有应用前途。 本文介绍了YH(?)的微生物学特征及应用特性,同时,探索和改进了一些实验室进行固态模拟发酵的方法。     

THE INFLUENCE OF DISSOLVED OXYGEN ON FERMENTATION IN A SELECTED CONTINUOUS SYSTEM

A system of continuous fermentation, in which all the sequential changes which normally occur during the course of a batch fermentation are reproduced, has been used to study the effects of several concentrations of dissolved oxygen in the wort on the behaviour of the yeast and on the development of compounds which influence aroma and flavour in the subsequent fermentation. Although the higher levels of oxygen resulted in slightly greater rates of yeast growth there were few or no detectable differences in aroma and flavour. It is concluded that, under the operational conditions of this system, the concentration of dissolved oxygen in wort is of relatively minor importance and that it has little influence upon the subsequent fermentation.