低糖啤酒发酵过程中糖组分的HPLC动态分析

运用HPLC法对低糖啤酒发酵过程中糖组分进行了动态分析，发现麦芽三糖的利用效率是发酵度提高的关键所在。     

高效液相色谱法测定麦汁、发酵液和啤酒中的嘌呤含量

通过高效液相色谱法测定了不同浓度的麦汁、发酵液及成品啤酒中的嘌呤含量,分析了嘌呤在发酵过程中的变化情况。此外,还分析了不同辅料比的麦汁中嘌呤含量的差异,发酵液中含有酵母与不含有酵母时检测的差异性,以及活性碳吸附对啤酒中嘌呤含量的影响。该研究为开发低嘌呤啤酒提供了可靠的检测方法和研究思路。     

3-甲硫基丙醛对啤酒麦汁味的影响及其GC/MS定量检测方法的建立

对3-甲硫基丙醛在啤酒中的风味特点及对啤酒麦汁味的影响进行了研究,并对其在啤酒中的阈值进行了测定,研究结果表明啤酒中3-甲硫基丙醛具有类似于谷物蒸煮的味道,描述为麦皮味,与麦汁味相近,且其含量的高低与麦汁味成显著正相关,可以用3-甲硫基丙醛作为表征啤酒麦汁味的指标。经感官品评测定其在啤酒中的差别阈值为5.0μg/L。对样品进行蒸馏萃取结合GC-MS,建立了一种测定麦汁或啤酒中3-甲硫基丙醛的方法,采用外标法定量,该法的相关系数为0.9952,精密度为4.57%,回收率为83.71%～92.48%,检出限为0.015μg/L。应用这一方法检测了不同啤酒中3-甲硫基丙醛的含量,发现普通啤酒都在50μg/L以下,结合其差别阈值,得到啤酒中3-甲硫基丙醛的控制标准为不超过55μg/L。     

The Gel Filtration Chromatographic‐Profiles of Proteins and Peptides of Wort and Beer: Effects of Processing — Malting,Mashing, Kettle Boiling,Fermentation and Filtering

Barley and malt proteins, of infusion (IoB) and decoction (EBC) mashing worts as well as commercial wort and beer, obtained from the Castlemaine Perkins brewery, Brisbane, were gel filtered, with or without further treatments. A general, similar pattern of protein and peptide profiles emerged from barley malt and beer. This confirmed the widely assumed fact that beer proteins descend from barley, some transformed and others perhaps mostly unchanged by processing. In the gel‐filtrate profiles, a maximum of 8 or 9 fractions were discerned. These fractions were collected and quantified for protein contents and amino acid compositions. The first four fractions contained the proteins and polypeptides of molecular weight higher than 14,000. Consequently, the remaining fractions contain the smaller peptides (<14,000), that were completely removed by dialysis. The effects of processing on proteins and peptides varied contingent upon the type of processing step considered and the pre‐chromatographic treatment. Malting was the most effective process remarkably increasing the soluble protein contents, especially the smaller peptide fractions and the colour development. This is the first report, as far as we are aware of, on the gel filtration profiles of wort and beer low molecular weight peptides including those of barley wort. The importance of the smaller peptides in foam formation and retention cannot be overemphasised. The amino acid composition of the fractions revealed much more diversity than was observed in the comparison of the profiles. Proline content of fraction 1 resembled that of barley soluble proteins while fractions F2, F3 and F4 that of glutelin and only fraction 8 that of hordein. The latter, suggests that hordeins or, at least the peptide products rich in proline, are likely to be completely digested to amino acids, during malting.     

Sensory and Instrumental Flavour Analysis of Wort Brewed with Dark Specialty Malts

In order to explore the flavour produced by dark specialty malts, wort samples were brewed with different malts and evaluated by sensory and instrumental analysis. With increasing wort colour, a trained tasting panel detected more intense bitter and burnt flavours, whereas sweet and husky flavour notes decreased. Conversely, caramel and bread‐like flavour attributes had a maximal intensity for the intermediate wort colours. Tasting of 20 EBC worts indicated that the flavour profile was significantly affected not only by malt level and malt colour but also by malt origin. Furthermore, the darkest caramel malt (480 EBC units) was found to contain most Maillard aldehydes as determined by the reaction with thiobarbituric acid. Similarly, other intermediate products of the Maillard reaction such as acetic acid, diacetyl and 2,3‐pentanedione were found to arise in a higher concentration in dark caramel malts (220–480 EBC units) than in roasted malt (1200 EBC units). Dynamic headspace GC/MS further revealed that brewing with dark specialty malts considerably increased the level of 3‐methylbutanal, its aldol condensation product (2‐isopropyl‐5‐methyl‐2‐hexenal) and heterocyclic Maillard compounds. In contrast, dark malts drastically reduced the amount of hexanal in wort. By means of HPLC, it was established that only extreme roasting temperatures lead to the thermal degradation of ferulic acid to 4‐vinylguaiacol in malt.     

Analysis of flavour compounds in beer with extruded sorghum as an adjunct using headspace solid‐phase micro‐extraction and gas chromatography–mass spectrometry

Sorghum is a widely used adjunct that is used in the production of beer and increasingly affects beer flavour as the amount added increases. The aim of this work was to establish a simple, solvent‐free technique, without derivatization, to analyse flavours and typical volatile compounds present in extruded and unextruded sorghum beer, and to compare the flavour differences of the two types of beer. Headspace solid‐phase micro‐extraction gas chromatography–mass spectrometry was used to determine the flavours in the two beers and eight typical volatile compounds were quantified using GC. Forty‐five flavour compounds were identified and quantified in extruded white sorghum beer, while 31 flavour compounds were identified in unextruded white sorghum beer. Extruded or unextruded white sorghum can be used to produce ale beer, but the primary flavour content in the extruded white sorghum beer was higher than in the unextruded white sorghum beer. Copyright © 2016 The Institute of Brewing & Distilling     

采用气相色谱质谱分析啤酒中的风味物质

采用静态顶空 (SHS)、固相微萃取 (SPME)和蒸馏 乙酸乙酯萃取 (DEE) 3种方法处理啤酒样品 ,结合气相色谱 质谱 (GC/MS) ,共分离定性 74种微量香味物质。其中静态顶空进样方法最为简便 ,固相微萃取法分析的物质最为广泛 ,蒸馏萃取法的操作较为繁琐 ,但是能够分离出指示啤酒老化程度的物质———糠醛。     

Analysis of Selected Esters in Beer: Comparison of Solid‐Phase Microextraction and Stir Bar Sorptive Extraction

Esters represent one of the most important flavour groups in beer. The aim of this work was focused on the comparison of two optimized, simple, rapid and low cost methods, the solidphase microextraction technique and the stir bar sorptive extraction technique, for the determination of beer esters, in particular isoamyl acetate, ethyl caproate, ethyl caprylate, ethyl caprate, phenylethyl acetate, ethyl laurate, ethyl myristate, and ethyl palmitate. Subsequent gas chromatographic analyses with flame ionization detection were used for the determination of these compounds. Linearity, recovery, and repeatability of these methods were compared. Working parameters of both procedures were similar and characterized by high repeatability (2.1–7.3%) and good linearity (correlation coefficient ranging from 0.9991 to 0.9999). Results obtained by these two procedures were in good correlation.     

Influence of Lauter Turbidity on Wort Composition,Fermentation Performance and Beer Quality in Large‐Scale Trials

Different lauter turbidities (standard 43 EBC vs. turbid 82 EBC on average) were obtained by variation of the lauter procedure, particularly deep raking, in this study. The resulting worts were used for repitching the respective yeast into six subsequent fermentation cycles. The resulting beers were investigated in terms of flavour quality, flavour stability, non‐biological stability and foam stability. Worts gained from turbid lautering showed very similar analytical data compared to the controls (except for a slight but significant increase in linoleic acid). There was an improvement in fermentation performance in terms of a pH decrease and a decrease in extract. The resulting beers were quite similar, and the staling indicators increased slightly, but not significantly, due to turbid lautering. Both types of beer were evaluated on tasting as being of a high flavour quality and neither a professional panel nor a non‐professional (customer) panel was able to distinguish the difference, between standard and turbid lautering, in terms of fresh and forced aged beers. Due to turbid lautering the non‐biological stability appeared to be slightly, but not significantly, decreased while on the other hand the foam stability was significantly improved due to turbid lautering. In conclusion, fermentation performance may be improved by more turbid lautering, and the negative consequences often reported for the resulting beers appear to be overestimated, since the quality parameters of the final beers had not deteriorated significantly.     

Comparison of volatile compounds in yoghurts made from cows’, buffaloes’, ewes’ and goats’ milks

The composition of the volatile fraction of yoghurts made from cows’, buffaloes’, ewes’ and goats’ milks was investigated during the 28 days of storage at 4 °C using solid‐phase microextraction technique (SPME) and gas chromatography coupled to mass spectrometry analysis (GC/MS). A total of 34 volatile compounds were identified in yoghurts during their storage at 4 °C, including aldehydes, ketones, alcohols, esters, acids, terpenes, hydrocarbons and sulphur compounds. In this study, acetaldehyde, diacetyl and acetoin, considered as the major compounds of yoghurt, were detected in all yoghurts.     

SDE and SPME Analysis of Flavor Compounds in Jin Xuan Oolong Tea

Simultaneous distillation‐extraction (SDE) and solid phase micro extraction (SPME) are procedures used for the isolation of flavor compounds in foods. The purpose of this study was to optimize SDE conditions (solvent and time) and to compare SDE with SPME for the isolation of flavor compounds in Jin Xuan oolong tea using GC‐MS and GC‐O. The concentration of volatile compounds isolated with diethyl ether was higher (P < 0.05) than for dichloromethane and concentration was higher at 40 min (P < 0.05) than 20 or 60 min extractions. For SDE, 128 volatiles were identified using GC‐MS and 45 aroma active compounds using GC‐O. Trans‐nerolidol was the most abundant compound in oolong tea. The number of volatiles identified using GC‐MS was lower in SPME than SDE. For SPME, 59 volatiles and 41 aroma active compounds were identified. The composition of the volatiles isolated by the 2 methods differed considerably but provided complementary information.     

The profile in polyphenols and volatile compounds in alcoholic beverages from different cultivars of mulberry

Abstract: Mulberry fruits have different chemical compositions because of cultivar variation. In this study, polyphenol profile and volatile composition of alcoholic beverages produced from different mulberries of Da 10, Hongguo 2 hao, and Hongguo 1 hao were investigated. Statistically significant differences were detected in the chemical composition of the analyzed alcoholic beverage samples. The beverage of Da 10 possessed the highest content of total phenols, total flavonoids, and total anthocyanins, which was determined by spectrophotometry analysis, contrarily Hongguo 1 hao beverage showing the lowest. Phenolic acids and flavonols were analyzed by high performance liquid chromatography analysis. Protocatechuic acid was the main phenolic acid in all analyzed alcoholic beverage samples, and its concentration ranged from 8.20 mg L^?1 (Hongguo 1 hao beverage) to 29.98 mg L^?1 (Da 10 beverage). High level of flavonols was found in both Da 10 and Hongguo 2 hao beverage samples, whereas Hongguo 1 hao beverage sample was characterized with lower level of flavonols. Furthermore, volatile compounds were analyzed by solid phase microextraction‐gas chromatography mass spectrometry analysis. The amount of esters varied widely among the 3 alcoholic beverage samples. The concentration of aliphatic alcohols in Hongguo 2 hao and 1 hao beverage samples was higher than Da 10 sample, whereas Da 10 beverage sample contained more aromatic alcohols than the others. Hongguo 1 beverage sample showed the highest concentration of acetic acid. This study demonstrated that quantitative differences of phenolic compounds and volatile compounds among cultivars were significant, which highly affected the quality of alcoholic beverage from mulberry. Practical Application: Mulberry fruits had different chemical compositions because of cultivar variation. The analyzed Da 10 cultivar of mulberry appeared to be a good raw material for alcoholic beverage‐making because of its high level of total sugar and acidity. This study demonstrated that alcoholic beverages from mulberry contain high amounts of polyphenols. These bioactive compounds may act synergistically to promote health, and reduce risk factors of chronic diseases.     

Comparison of Two Extraction Techniques,Solid‐Phase Microextraction Versus Continuous Liquid–Liquid Extraction/Solvent‐Assisted Flavor Evaporation,for the Analysis of Flavor Compounds in Gueuze Lambic Beer

Lambic is a beer style that undergoes spontaneous fermentation and is traditionally produced in the Payottenland region of Belgium, a valley on the Senne River west of Brussels. This region appears to have the perfect combination of airborne microorganisms required for lambic's spontaneous fermentation. Gueuze lambic is a substyle of lambic that is made by mixing young (approximately 1 year) and old (approximately 2 to 3 years) lambics with subsequent bottle conditioning. We compared 2 extraction techniques, solid‐phase microextraction (SPME) and continuous liquid–liquid extraction/solvent‐assisted flavor evaporation (CCLE/SAFE), for the isolation of volatile compounds in commercially produced gueuze lambic beer. Fifty‐four volatile compounds were identified and could be divided into acids (14), alcohols (12), aldehydes (3), esters (20), phenols (3), and miscellaneous (2). SPME extracted a total of 40 volatile compounds, whereas CLLE/SAFE extracted 36 volatile compounds. CLLE/SAFE extracted a greater number of acids than SPME, whereas SPME was able to isolate a greater number of esters. Neither extraction technique proved to be clearly superior and both extraction methods can be utilized for the isolation of volatile compounds found in gueuze lambic beer.     

Isolation,Identification, and Quantification of Lichenysin,a Novel Nonvolatile Compound in Chinese Distilled Spirits

Nonvolatile components influence overall flavor volatility and perception in alcoholic beverages. However, little information has been reported about the nonvolatile compounds in Chinese distilled spirits. For the first time, we isolated and identified a cyclic lipopeptide “lichenysin” as a novel nonvolatile compound in Chinese liquors, using preparative high performance liquid chromatography coupled with quadrupole‐time‐of‐flight mass spectrometer and nuclear magnetic resonance. The concentrations of lichenysin were quantified in 14 main types of bottled Chinese liquors by using ultra performance liquid chromatography coupled with triple quadrupole mass spectrometer. The concentrations of lichenysin in Chinese liquor ranged from 0.01 to 111.74 μg/L, where the concentration was the highest in Dongjiu liquor. Furthermore, we found that lichenysin selectively affected aroma volatility in the Chinese liquor, using the headspace solid‐phase microextraction coupled with gas chromatography‐mass spectrometry. The headspace concentrations of 2‐phenylethanol, phenol, and 4‐methylphenol significantly decreased by respectively 58%, 76%, and 59% in 3 Chinese commercial liquors with an increase in lichenysin. These results indicated that lichenysin could be a novel nonvolatile compound that selectively affected aroma volatility in Chinese liquors.     

Original article: Effects of continuous dense‐phase CO2 system on antioxidant capacity and volatile compounds of apple juice

The effects of different operating conditions applied to a continuous dense‐phase carbon dioxide (DPCD) system on antioxidant capacity and volatile compounds of apple juice were compared with current heat pasteurisation method. Only the microbial tests required by Italian Regulation to assure microbiological safety to ‘fruit juices and vegetables’ were performed, and DPCD‐treated (15 MPa, 35 °C, 15 min; 25 MPa, 35 °C, 15 min), heat‐pasteurised (75 °C, 15 s) and untreated apple juice samples were considered. The DPCD processing carried out at 15 MPa resulted as effective as 25 MPa in reducing microbial cells. Trolox equivalent of DPCD treated at 25 MPa (0.41 mm ) resulted significantly (P < 0.05) lower than DPCD treated at 15 MPa (0.48 mm ). Head space analysis of volatile compounds indicated the lowest decrease in apple aroma compounds (59% esters and 59% aldehydes) in DPCD treated at 15 MPa.     

运用顶空固相微萃取技术分析宣威火腿中的挥发性化合物

采用固相微萃取结合气相色谱 /质谱分析方法对宣威火腿中的挥发性化合物进行了提取和分析。试验结果表明 ,固相微萃取的时间和温度影响提取挥发性化合物的效果 ,试验选取 60℃、60min为提取条件 ,萃取物经气谱 /质谱分析 ,共鉴定出 72种化合物 ,其中烃类 2 8种、醛类 7种、醇类 4种、酸类 10种、酯类 5种、酮类 3种、杂环化合物 14种、酚类 1种。     

Development and Application of a Method for the Analysis of 9 Mycotoxins in Maize by HPLC‐MS/MS

A reliable and sensitive liquid chromatography/tandem mass spectrometry (LC‐MS/MS) method was developed for the simultaneous determination of aflatoxins (AFB₁, AFB₂, AFG₁, and AFG₂), ochratoxin A (OTA), deoxynivalenol (DON), zearalenone (ZEA), fumonisin B₁ (FB₁), and T2‐toxin in maize. The samples were first extracted using acetonitrile: water: acetic acid (79 : 20 : 1), and then further cleaned‐up using OASIS HLB cartridge. Optimum conditions for the extraction and chromatographic separation were investigated. The mean recoveries of mycotoxins in spiked maize ranged from 68.3% to 94.3%. Limits of detection and quantification ranged from 0.01 to 0.64 μg/kg and from 0.03 to 2.12 μg/kg, respectively. The LC‐MS/MS method has also been successfully applied to 60 maize samples, which were collected from Shaanxi Province of China. Twenty‐four of the total 60 samples (40%) were contaminated with at least 1 of these 9 mycotoxins. Occurrence of mycotoxins were 6.7%, 1.7%, 3.3%, 6.7%, 1.7%, 23.3%, and 3.3% for AFB₁, AFB₂, OTA, ZEA, DON, FB₁, and T2‐toxin, respectively. The results demonstrated that the procedure was suitable for the simultaneous determination of these mycotoxins in maize matrix.