DITERPENES AND DITERPENE ESTERS IN COFFEE

Coffee oil contains pentacyclic diterpenes as typical lipid constituents which have not been detected in any other foods. Major representatives are 16-O-methylcafestol, cafestol, and kahweol. Cafestol is contained in Arabica as well as in Robusta coffee. 16-O-Methylcafestol is found only in Robusta coffee. Larger quantities of kahweol were detected in Arabica coffee, but only trace amounts are present in Robusta.

In coffee oil, the diterpenes are hardly present in free form. They are largely esterified with fatty acids. Up to 14 fatty acid esters of 16-O-methylcafestol and cafestol have been identified. Palmitate followed by linoleate, oleate, stearate, arachidate, and behenate comprise almost 98% of the acid moieties. In Robusta coffee, the total amount of these six 16-O-methylcafestol esters are between 1.0 and 3.0 g/kg d.m. The contents of the corresponding cafestol esters vary between 2.0 and 8.0 g/kg d.m. in Robusta coffee and 9.0 and 22.0 g/kg d.m. in Arabica coffee.

Roasting has little influence on the percentage compositions of the diterpene ester fractions. Accordingly, the percentage distribution of diterpene esters in coffee powder is reflected in the resulting coffee brew. The absolute amounts depend on the type of preparation. In Scandinavian-type coffee, about 23% of the diterpene esters present in the powder can be found in the beverage. The lowest amount (0.3% of the initial quantity) is found in filtered coffee. An intermediate position is taken by espresso coffee with up to 2.5% of the initial concentration.     

YEAST ESTERASES AND AROMA ESTERS IN ALCOHOLIC BEVERAGES

It has been shown that the proportion of fatty acid ethyl esters retained by the yeast cell increases with increasing acyl chain length as the ester becomes more lipid soluble. The distribution of esters depends on the yeast strain and on the fermentation temperature; larger amounts of esters were found to transfer from the cells into the medium at higher temperature. It was shown that esterase activity is located both inside and outside the yeast cell plasma membrane. Intact yeast was capable of hydrolysing the ethyl esters of caproic, caprylic and capric acid. Acetate esters, were hydrolysed only very slowly or not at all. The hydrolytic activity of baker's yeast was studied with ethyl caprylate as substrate. The hydrolysis was very fast at the beginning. The equilibrium attained depended not only on the concentration of ester and alcohol but also on the pH, a higher amount of ester remaining in solutions of lower pH. It was also shown that the esterases possess appreciable ester synthesizing ability and an equilibrium was attained by incubating yeast with caprylic acid and ethanol. The experiments described show that the ester level in an alcoholic beverage, such as beer, is not dependent solely on the ester concentration formed during fermentation: in the presence of yeast the level can be shifted in either direction by changing temperature, pH or alcohol concentration — or the amount and type of yeast.     

ORGANOLEPTIC THRESHOLD VALUES OF SOME ALCOHOLS AND ESTERS IN BEER

In a Norwegian all-malt pilsener beer the organoleptic threshold values were determined for the following alcohols and esters: n-propanol, isobutanol, amyl alcohols (2-methyl butanol + 3-methyl butanol), 2-phenyl ethanol, ethyl acetate, isobutyl acetate, iso-amyl acetate, 2-phenyl ethyl acetate, ethyl caproate and ethyl caprylate. In addition, threshold values for a number of combinations of these alcohols and esters were determined, and in each case an additive effect was found.     

THE NATURE OF FATTY ACIDS AND CAPSANTHIN ESTERS IN PAPRIKA

SUMMARY– The triglycerides present in whole ground paprika and paprika pods were extracted and hydrolyzed. The fatty acids were methylated, separated by gas chromatography and identified by mass spectrometry. The whole paprika and pods, respectively, contained approximately 66 and 45% linoleic acid, 14 and 19% palmitic acid, 12 and 14% oleic acid and 5 and 17% linolenic acid. Small quantities of myristic and lauric acids and traces of capric, stearic and palmitoleic acids also were present. Capsanthin, which amounted to 35% of the total carotenoids, occurred as the dilaurate ester. It was isolated from paprika by thin-layer chromatography after interesterification of the triglycerides. Capsanthin dilaurate, synthesized in the laboratory, gave identical R_f value and infrared and visible spectra to those of the naturally occurring compounds.     

AMINO ACID ESTERS IN BEER

The ethyl esters of valine, leucine and iso-leucine have been detected in a range of commercial and experimental beers at levels between ca. 3 ppb and 71 ppb. However these compounds have been shown to have no noticeable effect on beer flavour at levels up to at least 12 ppm.     

α-生育酚酯类产品及其制备方法

生育酚酯类产品化学稳定性好，是维生素E系列产品的重要商品表现形式。生育酚酯种类很多，药理功能不尽相同。一些生育酚酯的生物活性比生育酚的高，有些生育酚酯更容易被人体吸收，还有一些生育酚酯则具有良好的表面活性。这些性质大大扩展了维生素E的应用领域，使之广泛应用于医药、食品、化妆品及饲料工业。     

COFFEE DRYING IN A ROTARY CONDUCTION-TYPE HEATING UNIT

Parchment coffee (Arabica) was dried from an initial moisture content of about 90% to 10% dry basis (db) in a recirculating rotary conduction type heating unit at controlled plenum temperatures of 100, 120 and 140C or controlled product temperatures of 50, 60, and 70C. the temperature of the plenum or moving beans could be maintained at specified levels with small variations during coffee drying experiments. the color and specific gravity of coffee beans exhibited minimum changes as a result of drying operations. the susceptibility of coffee beans to breakage decreased with the lowering of moisture and attained minimum values in the moisture content range of 20 to 30% db. the breakage susceptibility increased sharply with further reduction in moisture content. A drying model, which considered product temperature‐time history alone under different operating conditions, estimated the change in moisture content adequately. Such a model could be used for computer‐based control of the coffee drying process.     

与专家略谈咖啡

咖啡,这种备受外国人喜爱的饮料。目前在中国可以说还处在刚成长的阶段,人们对仪咖啡的爱好,一直维持逐年增长的趋势,现阶段中国的家庭咖啡消费量也以每年40%的速度增长,同时年度零售咖啡销量也增长了25%,并且继续保持强劲的增长势头。中国目前有着1.5亿中高收入年轻专业人士,他们就是推动这个庞大消费市场的主流基础。     

ANTIMICROBIAL ACTIVITY OF FATTY ACIDS AND THEIR ESTERS AGAINST A FILM-FORMING YEAST IN SOY SAUCE

Antimicrobial activity of fatty acids and their glycerol and sugar esters against a film-forming yeast isolated from raw soy sauce was determined in diluted soy sauce. In a series of fatty acids (alkyl chain length of 7, 9, 11 and 13) and their monglycerides, capric acid and monolaurin had the highest inhibitory activity. Two selected sugar esters (sucrose monocaprate and sucrose monolaurate) could not completely inhibit the growth of test organism throughout 3 weeks.     

THERMOPHYSICAL PROPERTIES OF FRESH AND ROASTED COFFEE POWDERS1

The present work deals with experimental determination of bulk specific heat, bulk thermal conductivity, bulk and true density and moisture content of Columbian and Mexican coffee bean powders. Specific heat was determined by DSC, thermal conductivity by modified Fitch apparatus, density by stereopycnometer and moisture contents by standard vacuum oven method. Specific heat values showed marginal rise over the temperature range (45 to 150C) studied. Thermal conductivity values, determined in the temperature range of 20–60C were not found to have any definite trend with rise in moisture in the experimental range of 4.8 to 9.8% moisture (dry basis). Bulk density of powders varied appreciably (1.298 to 0.882 g.cm^?3), while the change was negligible for true density (1.361 to 1.092 g.cm^?3) with the degree of roasting. Statistical analysis of the data shows the reliability of the experimental determinations. Suitable correlations were developed to determine bulk specific heat and bulk density.     

老挝咖啡的挥发和半挥发性成分提取分析

采用超声波提取(UE)和同时蒸馏萃取(SDE)两种前处理方法提取老挝咖啡中的挥发性成分,利用气相色谱-质谱(GC-MS)联用仪进行定性检测,并加入乙酸苯乙酯作为内标进行定量分析.实验结果表明:两种萃取方法共鉴定出挥发性成分77种,共同组分26种.其中超声级萃取以正己烷为溶剂鉴定出18种,以二氯甲烷为溶剂鉴定出28种,以甲醇为溶剂鉴定出41种,同时蒸馏萃取鉴定出54种.咖啡的主要挥发性成分有咖啡因、棕榈酸、亚油酸-2-氯乙酯、油酸、硬脂酸、醋酸孕烯醇酮等.超声波提取适用于主要成分和高沸点物质的提取,而同时蒸馏萃取更适合于低分子量、低沸点致香物质的萃取.两者各有所长,可根据需要来选择.