Effect of redfish meal enriched diets on the taste and n-3 pufa of 42-day-old broiler chickens

Broiler chickens were fed diets supplemented with redfish meal at levels of 4,8 and 12 %. A control group was fed with an all-vegetable protein diet. After 42 days the birds were slaughtered and edible tissues (white, dark and skin) were analysed for lipid content and composition. The white and dark meats were tasted organoleptically for the possible presence of ‘fishy’ off-flavours. There was no change in the content or class composition of the lipids with diet or sex of the bird, but in meats an increase in fish meal in the diet caused an increase in the level of n-3 polyunsaturated fatty acids present, especially 20: 5n-3 eicosapentaenoic acid, 22: 5n-3 docosapentaenoic acid and 22: 6n-3 docosahexaenoic acid at the expense of n-6 fatty acids. The enrichment was most pronounced in white meat of both male and female birds and could make a contribution of n-3 polyunsaturated fatty acids to the human diet quantitatively similar to that of an equal portion of lean white fish. Taste panel results showed that there was no significant difference in flavour or taste among any of the samples. There was a tendency for the 12% dietary group birds to be the least preferred, but no panelist detected ‘fishy’ flavours or objected to the taste of the meat.     

基于电子鼻和电子舌技术分析发酵鲟鱼加工过程中风味的变化

采用电子鼻、电子舌技术分别对新鲜鲟鱼、腌制鲟鱼和发酵鲟鱼（5 d、10 d、20 d、25 d、35 d）的气味和滋味进行检测,并结合感官评价方法,分析发酵鲟鱼加工过程中气味和滋味的差异,以期探寻一种快速、便捷、准确鉴定鲟鱼发酵程度的方法。结果表明,电子鼻的17个传感器和电子舌的5个传感器对不同处理阶段和不同发酵时间鲟鱼样品的气味与滋味响应强度均有差异,不同处理阶段和不同发酵时间鲟鱼样品气味差异明显,滋味差异不明显,说明电子鼻可有效区分不同处理阶段和不同发酵时间的鲟鱼,而电子舌对鲟鱼的发酵过程区分效果欠佳。不同处理阶段鲟鱼的气味差异主要存在于烃类、酯类、醛类、硫化物和胺类等化合物上。感官评价可以从外在分析发酵鲟鱼的滋味和气味及肉质,与电子鼻分析结果一致。     

Fermentation studies on maize during the preparation of a traditional african starch-cake food

The important micro-organisms of ‘ogi’ fermentation have been enumerated, isolated and identified. The moulds isolated consist of Cephalosporium, Fusarium, Aspergillus and Penicillium. Of the aerobic bacteria, only Corynebacterium and Aerobacter could be identified. Lactic acid bacteria present were found to be mainly Lactobacillus plantarum. There were also yeasts of which Candida mycoderma, Saccharomyces cerevisiae and Rhodotorula were identified. There was indication that, Corynebacterium hydrolysed the starch of maize to form organic acids. Aerobacter cloacae was shown to be capable of increasing the riboflavin and niacin content of the mash, while L. plantarum was mainly responsible for the production of lactic acid, the main flavour base of ogi. Saccharomyces cerevisiae and Candida mycoderma were also found to contribute to flavour acceptability.     

Sensory and chemical changes in five varieties of carrot (Daucus carota L) in response to mechanical stress at harvest and post‐harvest

Carrots harvested by hand or machine and given additional mechanical stress by shaking in a transport simulator were analysed for taste, flavour and content of sugars, terpenes, 6‐methoxymellein and ethanol as well as for ethylene production and respiration. Carrots stressed by shaking had higher ethylene production and respiration, higher content of ethanol and 6‐methoxymellein and lower levels of total terpenes, several individual terpenes and sugars. This corresponded to a higher sensory score for ethanol flavour and odour, bitter taste, earthy flavour, terpene flavour, aftertaste and sickeningly sweet taste and a lower score for acidic taste and sweet taste as measured by an expert taste panel. Ethanol content was highly correlated with ethanol flavour and odour and sickeningly sweet taste. Of five varieties tested, ‘Bolero’ ‘Panter’ and ‘Yukon’ were most sensitive to mechanical stress, whereas ‘Napa’ and ‘Newburg’ were most resistant. Hand‐harvested carrots were not significantly different from machine‐harvested carrots as regards chemical or sensory variables. Principal component analysis showed only slightly different placing of these samples in the score plot. A digital carrot could monitor the degree of mechanical stress to which the carrots were subjected. © 2001 Society of Chemical Industry     

The temperature dependent functionality of Brettanomyces bruxellensis strains in wort fermentations

In recent years, Brettanomyces bruxellensis has found increasing application in brewery fermentations. Indeed, B. bruxellensis contributes to the flavour profile of many Belgian beers, typically during secondary or spontaneous fermentation. In North America, the yeast is used in primary fermentation to produce beers with ‘Brett’ characteristics with ‘fruity’ and/or ‘funky’ sensory profiles associated with the production of volatile esters and phenols. However, little is understood about the factors that influence flavour metabolite production or fermentation rate in this yeast. Here, the impact of temperature is reported on fermentation efficiency, flavour metabolite production and carbon utilisation of one commonly used and eight poorly characterised B. bruxellensis strains during wort fermentation. A high degree of strain and temperature‐dependent variability was found in fermentation efficiency and metabolite production amongst B. bruxellensis strains. Further, fermentation efficiency and carbon utilisation were temperature dependent, while ester production increased at higher temperature and phenol production was strain and temperature independent. These results indicate significant strain and temperature dependent variation, suggesting the potential application of strain variability as a tool to achieve product diversity in B. bruxellensis primary fermentations. © 2019 The Institute of Brewing & Distilling     

Improvement of flavour compound synthesis in a mixed culture system at high temperature by solid‐state fermentation

In order to enhance the synthesis of flavour compounds in solid‐state fermentation (SSF) at a high temperature, Bacillus subtilis XJ‐013 and Saccharomyces cerevisiae Z‐06 were used as a mixed culture with Monascus HQ‐3. The culture temperature was enhanced from 37°C to 56°C by the synergetic effect, and the synthesis of esterase was enhanced from 85.43 U/g to 129.65 U/g in the mixed culture system (over 50% higher than that of the culture using a single strain). This resulted in the synthesis of favourable flavour compounds in the solid‐state fermentation. These results signified that a mixed culture of Monascus and S. cerevisiae was favourable for enzyme production. The mixed culture of Monascus and B. subtilis resulted in a high culture temperature that promoted flavour compound synthesis in the solid‐state fermentation system dramatically. These results present a model to explain the synergetic effects between the fungus and the Bacillus in the solid‐state fermentation. Copyright © 2015 The Institute of Brewing & Distilling     

蒸制鲟鱼肉特征性滋味组分的鉴定

为明确传统热加工鲟鱼肉特征性滋味组分,对蒸制鲟鱼肉中游离氨基酸、核苷酸、有机酸、甜菜碱及无机离子等滋味组分进行定量分析,并结合滋味活性值、滋味组分减缺、添加及重组实验探究蒸制鲟鱼肉的关键味觉化合物。结果表明：蒸制16 min鲟鱼肉的关键味觉化合物为甘氨酸、谷氨酸、丙氨酸、5’-一磷酸腺苷、5’-一磷酸肌苷、乳酸、琥珀酸、K＋、Na＋和Cl－;将10 种关键味觉化合物按其天然含量溶解在超纯水中制备简化重组液,简化重组液能够较为完整地复制完全重组液的味道,但与天然提取液相比,在鲜味上仍有所欠缺。     

The effect of supplementation of a white clover or perennial ryegrass diet with grape seed extract on indole and skatole metabolism and the sensory characteristics of lamb

Condensed tannin in the form of a grape seed extract (GSE) was dosed to weaned wether lambs fed white clover (WC) or perennial ryegrass (PRG) over a 9‐week period to determine whether the ‘pastoral’ flavour and odour of meat could be altered. The concentrations of the pastoral flavour compounds indole and skatole were determined in the rumen fluid, blood plasma and intermuscular fat. The odour and flavour of fat and meat from the slaughtered lambs was assessed by a trained panel. The rumen fluid and blood plasma concentrations of indole and skatole were higher in those lambs fed WC compared to PRG (P < 0.05) and the overall meat flavour intensity was greater when feeding WC (P < 0.01). The observed concentration of indole and skatole in the fat between WC and PRG feeding treatments was not statistically different. Power analysis indicated that increasing the number of lambs per treatment group from 20 to 65 would result in a higher fat skatole concentration (P < 0.05) being detected in lambs fed WC compared to PRG. Dosing with GSE gave a small reduction in skatole concentration in the rumen fluid and reduced plasma concentration of indole and skatole (P < 0.001). Odour and flavour scores of the fat and meat samples were not particularly high however, dosing with GSE lowered the overall and sweet odour and the sheepy, camphor, faecal and barnyard flavour (P < 0.05). Although the plasma concentration of indole and skatole suggests that GSE reduced indole and skatole formation, the intermittent supply of the GSE to the rumen environment was not sufficient to reduce their concentration in the fat. Hence, the small difference in the scores for pastoral odour and flavour attributes associated with GSE treatment may arise from other unknown factors. From a primary investigation, there was no difference in the concentration of indole and skatole in fat samples collected from carcasses before and after chilling. Further investigations into meat pastoral flavour are warranted through feeding condensed tannin‐containing forages. Copyright © 2007 Society of Chemical Industry     

Pilot‐scale brewing using self‐cloning bottom‐fermenting yeast with high SSU1 expression

A pilot‐scale fermentation was performed using SSU1‐overexpressing bottom‐fermenting yeast strains constructed by ‘self‐cloning’. In these strains, the gene SSU1, encoding a plasma membrane protein that excretes sulphite, was highly expressed. The rate of fermentation of the two SSU1‐overexpressing strains tested showed some reduction during the mid‐fermentation phase as compared with the parental strain. These differences, however, did not affect overall fermentation and the final apparent extracts had decreased to a level normally obtained during brewing. The concentration of hydrogen sulphide in the wort remained low during fermentation in the case of the two self‐cloning strains compared with the parent. The concentration of 2‐mercapto‐3‐methyl‐1‐butanol, a sulphur compound that causes an ‘onion‐like’ off‐flavour, was also reduced in the case of the self‐cloning strains, a result confirmed by sensory evaluation of the beer immediately after bottling. Furthermore, with these strains the anti‐oxidation potential of bottled beer, as measured by electron spin resonance, was improved and the concentration of trans‐2‐nonenal in bottled beer after 7 days of accelerated aging at 37°C was decreased. These observations, together with the lower stale flavour score determined by sensory evaluation of bottled beer after a month of aging at 25°C, indicated that the flavour stability of the beer had been successfully improved. Copyright © 2013 The Institute of Brewing & Distilling     

Microbial succession and metabolite changes during the fermentation of Chinese light aroma‐style liquor

A combination of culture‐dependent and culture‐independent methods and SPME–GC–MS were used to monitor changes of bacterial and yeast communities, and flavour compounds during the fermentation process of Chinese light aroma‐style liquor. Bacillus and Lactobacillus were the main bacterial genera. Pichia anomala, Saccharomyces cerevisiae and Issatchenkia orientalis were the dominant yeast species. There was a close relationship between fermentation time and the shift of microbial community. Compared with the microbiota in the fermentation of other style liquors, higher bacterial diversity and different non‐Saccharomyces composition led to a variety of metabolites. Metabolite analysis showed that esters, acids, alcohols, aromatic compounds and phenols were the main flavour components and most of them were synthesised in the latter phase of fermentation. Principal component analysis further demonstrated that Bacillus and yeast were the most influential microorganisms in the first 10 days of fermentation, and lactic acid bacteria predominated in the later phase. Lactic acid bacteria regulated the composition of other bacteria and yeast, and synthesised flavour compounds to affect the organoleptic properties of liquor. S. cerevisiae and P. anomala were two important yeast species responsible for the characteristic aroma of liquor. These results present a comprehensive understanding of microbial interaction and potential starter cultures to produce desirable liquor quality. © 2018 The Institute of Brewing & Distilling     

Application of Plackett–Burman experimental design for investigating the effect of wort amino acids on flavour‐active compounds production during lager yeast fermentation

Aroma‐active higher alcohols and esters are produced intracellularly in the cytosol by fermenting lager yeast cells, which are of major industrial interest because they determine aroma and taste characteristics of the fermented beer. Wort amino acid composition and their utilization by yeast during brewer's wort fermentation influence both the yeast fermentation performance and the flavour profile of the finished product. To better understand the relationship between the yeast cell and wort amino acid composition, Plackett–Burman screening design was applied to measure the changes in nitrogen composition associated with yeast amino acids uptake and flavour formation during fermentation. Here, using an industrial lager brewing strain of Saccharomyces pastorianus , we investigated the effect of amino acid composition on the accumulation of higher alcohols and volatile esters. The objective of this study was to identify the significant amino acids involved in the flavour production during beer fermentation. Our results showed that even though different flavour substances were produced with different amino acid composition in the fermentation experiments, the discrepancies were not related to the total amount of amino acids in the synthetic medium. The most significant effect on higher alcohol production was exercised by the content of glutamic acid, aromatic amino acids and branch chain amino acids. Leucine, valine, glutamic acid, phenylalanine, serine and lysine were identified as important determinants for the formation of esters. The future applications of this information could drastically improve the current regime of selecting malt and adjunct or their formula with desired amino acids in wort. Copyright © 2017 The Institute of Brewing & Distilling     

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.     

Contribution by Saccharomyces cerevisiae Yeasts to Fermentation and Flavour Compounds in Wines from cv. Kalecik karasi Grape

The effect of indigenous and commercial S. cerevisiae yeasts on fermentation and flavour compounds of wines was examined in pasteurised grape juice. The flavour compounds were analysed and identified by GC‐FID and GC‐MS, respectively and in general, the amounts of these volatiles were increased by the use of both indigenous and commercial yeasts. The levels of isoamyl alcohol, isoamyl acetate, ethyl octanoate and ethyl deconoate exceeded flavour thresholds. All grape juices were fermented to dryness. Selected yeasts produced higher ethanol concentrations compared to spontaneous fermentations.     

THE OCCURRENCE OF TWO GEOMETRICAL ISOMERS OF 2,4,5-TRIMETHYL-1,3-DIOXOLANE IN BEER

Two geometrical isomers of 2,4,5-trimethyl-1,3-dioxolane have been detected in a range of commercial and experimental beers at levels up to ca 0.1 ppm. These compounds, plus a number of other dioxolanes, are present in unboiled wort but are lost by evaporation during wort boiling. The trimethyldioxolanes are then reformed during subsequent fermentation. The flavour threshold of a mixture of the two trimethyldioxolanes was found to be ca 0.9 ppm, at which concentration it produced in beer ‘phenolic’ and ‘astringent/drying’ flavour notes. However, these compounds are not present in sufficiently high concentrations to make a significant contribution to the flavour of beer.     

The Production of Isoamyl Acetate from Amyl Alcohol by Saccharomyces cerevisiae

Isoamyl acetate is a natural flavour ester, widely used as a source of banana flavour by the food industry. Fusel alcohols such as amyl alcohol are produced in significant quantities as a waste product, sometimes referred to as “lees oil” or “fusel oil”, of the alcohol distilling industry. By manipulation of brewing yeast fermentation conditions, a significant portion of added amyl alcohol was shown to be converted to isoamyl acetate. This was achieved by the addition of L‐leucine and amyl alcohol in fermentations carried out by a high ester‐producing brewing yeast strain of Saccharomyces cerevisiae and by the use of alkaline fermentation conditions coupled with high gravity media. Mutant strains selected on 5,5,5 trifluoro‐DL‐leucine produced substantially high levels of isoamyl acetate. The adjustment of fermentation conditions outlined in this paper may act as a stepping stone for the potential use of Saccharomyces cerevisiae and other yeasts to produce high levels of natural flavour esters.     

Impact of maceration time on colour‐related phenolics,sensory characteristics and volatile composition of mulberry wine

This study investigated the effect of maceration treatment on colour‐related phenolics, sensory characteristics and volatile composition in mulberry wine. Pre‐fermentation maceration was performed for 2 days (‘short’), 6 days (‘medium’) and 8 days (‘long’), respectively, followed by the same fermentation process. Results showed that the long maceration (LM) caused higher level of anthocyanins in wine, especially cyaniding‐3‐O‐rutinoside, cyaniding‐3‐O‐glucoside and dephinidin‐3‐O‐glucoside, whereas the short maceration caused lower level of phenolic acids in wine. The medium maceration (MM) wine showed the highest level of flavonols but the lowest concentration of flavan‐3‐ol. The LM wine exhibited greater red tone and colour intensity accompanied by higher amounts of free and copigmented anthocyanins. The LM wine showed lower levels of alcohols, acids, terpenoids, benzenes and sulphur compounds, whereas the lowest level of esters was found in the MM wine. The LM wine had reduced fruity and floral aroma and overall flavour complexity compared with the other wines. Copyright © 2018 The Institute of Brewing & Distilling     

类胡萝卜素降解对枸杞酒特征香气的影响

为探究类胡萝卜素降解后产生的降异戊二烯类化合物对枸杞酒特征香气的影响,采用一株可降解类胡萝卜素的库特氏菌进行实验。分别在枸杞渣中接种库特氏菌,枸杞清汁中接入工业酿酒酵母,发酵结束后混合;在枸杞汁中加入库特氏菌酶制剂,辅助工业酿酒酵母发酵;将高压灭菌的枸杞渣加入枸杞清汁后接种工业酿酒酵母发酵,并以正常发酵工艺酿制的枸杞酒作为对照。采用顶空固相微萃取及气相色谱质谱联用（GC-MS）法,对枸杞酒香气成分进行检测,并通过感官评分法评价3种降解类胡萝卜素方式对枸杞酒香气的影响。结果表明,库特氏菌酶制剂辅助发酵组枸杞酒香气和口感均为最佳,高压灭菌后发酵组澄清度最好。因此,在枸杞酒酿造过程中,可以采用库特氏菌酶制剂对枸杞汁进行降解处理,在此之前对枸杞渣可适度配合使用高压灭菌,从而改进枸杞酒的酿造工艺,提升枸杞酒香气。     

Sensory quality of ethylene‐exposed carrots (Daucus carota L,cv ‘Yukon’) related to the contents of 6‐methoxymellein,terpenes and sugars

Carrots were analysed for taste and odour and for contents of terpenes, 6‐methoxymellein and sugars during 3 weeks storage at 15 °C in an atmosphere containing ethylene (1 µl l⁻¹). The ethylene treatment caused an increase in 6‐methoxymellein and the conversion of higher amounts of sucrose to fructose and glucose compared to control carrots stored in air. This corresponded to higher sensory scores for bitterness and terpene flavour and a lower score for sweetness, as measured by an expert taste panel. Principal component analysis showed a more expressed bitter taste, earthy flavour, green flavour, terpene flavour and aftertaste in the ethylene‐treated carrots. Correlations were found between sweet taste and the content of sucrose (r = 0.91, p < 0.005) and between the contents of various terpenes (particularly γ‐terpinene, limonene and caryophyllene) and terpene flavour, green flavour, aftertaste and bitter taste (r ≥ 0.72, p < 0.05). In the air‐stored carrots these off‐flavours seemed to be masked by a high sucrose content. © 2000 Society of Chemical Industry