Representativeness of coffee aroma extracts: a comparison of different extraction methods

Analyses for the investigation of aroma components are routinely performed on coffee aromatic extracts. Various extraction methods exist. Ideally, the extraction method used should provide an extract with sensory characteristics as close as possible to the complete product. This is particularly relevant in the case of coffee, as no single key compound has been demonstrated as being responsible for the typical flavour of roasted and ground coffee. The purpose of this study was to compare various methods to see which provided an aromatic extract most representative of coffee. Five different extraction methods were compared: supercritical fluid extraction with carbon dioxide, simultaneous distillation extraction, oil recovery under pressure and vacuum steam-stripping with water or with organic solvent. In addition, Arabica Colombia coffee was used at three different roasting levels, i.e. green coffee as well as the same coffee light-roasted and medium roasted. Sensory testing of the extracts showed that vacuum steam-stripping with water provided the most representative aroma extract, for all three coffees.     

Isolation and Partial Characterization of a Natural Antioxidant from Shrimp (Pandalus jordani)

The nature of a natural antioxidant present in shrimp was investigated. From several solvents used in the extraction process, ethanol proved most effective. A diethyl ether extract exhibited no antioxidant activity. The compound responsible for the antioxidant effect was present in very low concentrations in its natural source. The chemical characteristics and chromatographic properties suggested that it was a polyhydroxylated derivative of an aromatic amino acid.     

Analysis of benzo[a]pyrene content from smoked food products in Korea

The content of benzo[a]pyrene (BaP) was evaluated from 100 smoked food products commonly consumed in Korean market with HPLC. Analysis method for BaP content on smoked food products was evaluated and validated. For validation, the efficiency of saponification time and solid phase extraction cartridges were evaluated. During 1–4 h of saponification, recovery of BaP was ranged from 90.17 to 98.87%. Among the 5 tested cartridges including florisil, silica gel, and alumina cartridges (acidic, basic, and neutral), the most efficient cartridge was florisil cartridge and the recovery of BaP was 98.87%. Limit of detection and limit of quantification was 0.03 and 0.09, respectively. As a result of BaP content analysis from smoked food products, the average BaP content was 0.45 μg/kg and the highest content of BaP was 2.87 μg/kg detected in smoked salmon product.     

A new quick solid-phase extraction method for the quantification of heterocyclic aromatic amines

A new solid-phase extraction (SPE) method using only one SPE cartridge is described as a clean-up procedure for the determination of heterocyclic aromatic amines (HAAs). In particular, the polar HAAs imidazoquinolines and imidazoquinoxalines, which are well-known toxic compounds in thermally treated food, can be determined by this quick and simple method. For validation of the method meat extracts were analyzed. For determination of the percentage recovery and standard deviation the beef extract was spiked (40 ng/g of each HAA) and analyzed 10 times. The polar HAAs were determined in this meat extract with a recoveries of 62 % to 95% and standard deviations of 3% to 5%. The recovery rates of the less polar HAAs Harman and Norharman were much lower (25±5% to 32±5%). The limit of detection for polar and less polar HAAs was between 3 ng/g and 9 ng/g in the meat extract matrix. The method comprises extraction with methanolic NaOH, centrifugation and SPE using a commercially available polystyrene copolymer cartridge. After different washing steps the eluate was analyzed by high-performance liquid chromatography with diode-array detection. The advantages of this new method are the reduced amounts of time and organic solvents required. Received: 29 November 1999 / Revised version: 21 February 2000     

Determination of biogenic amines in cheese using HPLC technique and direct derivatization of acid extract

Cheeses are among those high-protein-containing foodstuffs in which enzymatic and microbial activities cause the formation of biogenic amines from amino acids decarboxylation. Most of the methods for amine determination in this products involve acid extraction followed by a liquid–liquid purification step to selectively separate amines and amino acids. In this work a simple direct derivatization of the acidic extract with dansyl chloride (DCl) was applied. After an extraction step with diethyl ether, the amines were separated on a Kromasil C18 column using a water–acetonitrile elution gradient. Taking into consideration the recovery and repeatability data we can conclude that, when free amino acid determination is not of concern, the direct DCl derivatization procedure can be applied also for cheese samples with high free amino acid contents.     

Technical note: Simultaneous carotenoid and vitamin analysis of milk from total mixed ration-fed cows optimized for xanthophyll detection

Concentrations of retinol, α-tocopherol, and major carotenoids in dairy products are often determined simultaneously by liquid chromatography. These compounds have different polarity and solubility; thus, extracting them simultaneously can be difficult and inefficient. In milks with low carotenoid concentrations, the xanthophylls lutein and zeaxanthin may not be completely resolved using common extraction techniques. A simplified method was developed to optimize extraction efficiency and the limit of detection and limit of quantification (LoQ) of lutein and zeaxanthin in bovine milk without decreasing sensitivity to other vitamins or carotenoids. The developed method evaluates lutein, zeaxanthin, β-carotene, retinol, and α-tocopherol simultaneously by ultra-high performance liquid chromatography–photodiode array detection. Common saponification temperatures (40–60°C) and concentrations of KOH in water (10–50% KOH wt/vol) were evaluated. Multiple solvents were evaluated for optimal xanthophyll extraction (diethyl ether, dichloromethane, hexane, and tetrahydrofuran) following saponification. The limit of detection and LoQ were defined as 3:1 and 10:1 signal-to-noise ratio, respectively. All experiments were performed in triplicate. The optimal saponification procedure was a concentration of 25% KOH at either 40 or 50°C. Saponified extracts solubilized in solutions containing diethyl ether had greater concentrations of lutein- than hexane- or tetrahydrofuran-based solutions, with peak areas above LoQ values. The solution containing diethyl ether solubilized similar concentrations of retinol, α-tocopherol, and β-carotene when compared with other solutions. The proposed optimized method allows for the simultaneous determination of carotenoids from milk with increased lutein and zeaxanthin sensitivity without sacrificing recovery of retinol, α-tocopherol, and β-carotene.     

紫苏饼粕的残油醇提工艺及品质分析

为提取紫苏饼粕残油,减少有毒有机溶剂残留和污染,同时获得低脂、高蛋白紫苏饼粕,采用95%乙醇浸提法提取紫苏饼粕残油。在单因素试验的基础上,选出最优浸提温度、浸提次数、液固比、浸提时间。通过正交试验优化获得的工艺条件为:浸提温度75℃、浸提次数5次、液固比3.50:1、时间3 h。在该工艺下对紫苏饼粕残油的提取率可达96.04%,紫苏饼粕含油率降至0.51%,蛋白富集率提升至57.90%。对紫苏籽压榨油、紫苏饼粕乙醇浸提油及石油醚浸提油进行理化性质比较,结果表明三种油在酸值、过氧化值、碘值、皂化值方面均符合国家标准,其中石油醚浸提油的酸值和过氧化值较大分别为3.65 KOH/(mg/g)和5.96 mmol/kg,乙醇浸提油次之,低温压榨油较小为3.30 KOH/(mg/g)和5.22 mmol/kg。碘值无显著差异,而浸提油的皂化值要大于低温压榨油。通过气相色谱(GC)分析,乙醇浸提油的亚麻酸相对含量及不饱和脂肪酸占总脂肪酸比例分别为59.60%和89.31%,略低于低温压榨油的61.09%和90.33%,高于石油醚浸提油的57.29%和86.10%。综合来看乙醇浸提油品质高于石油醚浸提油,略低于低温压榨油。     

双低油菜籽粕中甾醇提取

植物甾醇是植物中广泛存在一类具有重要生物活性物质。该文以双低油菜籽粕为原料,通过L_9(3~4)正交实验探讨从双低油菜籽粕中提取植物甾醇方法、工艺条件等。实验结果表明,在最佳条件下得率可达0.1426％(其含量为0.1531％,提取率可达93.1％)。本实验所选丙酮、石油醚、乙酸乙酯、苯、丙酮与石油醚混合物或乙酸乙酯与苯混合物等六种提取剂,除石油醚外其余提取剂对双低油菜籽粕均有良好提取效果,其中以乙酸乙酯提取效果较佳,且提取甾醇组分较全。     

酿酒酵母中提取麦角甾醇的研究

以酿酒干酵母为原料,在适量甲醇和氢氧化钾溶液中,95℃水浴皂化回流2．5h,用有机溶剂乙醚萃取麦角甾醇,减压浓缩富集。4～-7℃缓慢降温结晶,获得麦角甾醇粗品,产率为1．11%。将麦角甾醇粗品溶解于乙醚溶剂中,重结晶得到纯度较高的麦角甾醇晶体,平均产率为0．69%,提取率可达62．58%。采用电子扫描显微镜对恒温结晶和降温结晶得到的晶体进行晶貌观察,利用红外光谱法进行麦角甾醇的结构表征。     

A rapid method for the measurement of Leucaena spp proanthocyanidins by the proanthocyanidin (butanol/HCl) assay

Proanthocyanidin (PA) extraction, sample preparation and proanthocyanidin assay (butanol/HCl) reaction conditions were evaluated for measuring PA in Leucaena spp leaf material. The optimal conditions for extracting PA from leaf tissue are described, with short sequential sonications in 70% aqueous acetone being as efficient as prolonged sequential mechanical agitation. In methanol–based extracts, after back extraction to remove pigments, increasing the water content of the reagent/sample matrix suppressed colour development. The addition of low concentrations of Fe³⁺ to the butanol/HCl reagent enhanced colour yield, but higher Fe³⁺ concentrations suppressed colour development. The presence of ascorbic acid in the sample extract was shown to increase colour development. Varying the reagent: sample extract ratio from 4:1 to 6:1 significantly decreased colour yield, but neither ratio was different from 5:1. Optimum conditions for the PA assay were as follows: a water content of 8%, the omission of Fe³⁺, a reagent: sample extract ratio of 5:1 and the addition of ascorbic acid to the stock PA standard solution to match that contributed by the extract in the final mixture. Sample preparation procedures, using back extraction to remove pigments and non-PA phenolics with diethyl ether and ethyl acetate, respectively, were time-consuming and subject to PA losses. The measurement of PA directly in the 70% aqueous acetone extract eliminated these PA losses, but the PA assay required additional optimisation for direct analysis of crude acetone extracts. In the final optimised procedure, PA was extracted by sequential sonication with 70% aqueous acetone containing 5·26 mM sodium metabisulphite as the antioxidant. These extracts were directly analysed by the butanol/HCl reaction using a reagent: sample extract ratio of 5:1, the omission of Fe³⁺ from the butanol/HCl reagent and the addition of sodium metabisulphite to match that contributed by the extract. This produced consistent linear calibration curves over the range 25–1000 μg PA with an average recovery of 101%. © 1998 Society of Chemical Industry.     

甘露醇辛酸二酯的酶法合成、鉴定及其应用研究

脂肪酶催化合成甘露醇辛酸二酯,利用HPLC-MS确定产物,使用混合介质正己烷:乙醚(7:3)对目标产物进行萃取纯化,产物纯度达到90%以上。采用HPLC-MS、NMR确定目标产物为1,6-二辛酸甘露醇酯。将甘露醇辛酸二酯添加到不同植物油中,探讨在不同植物油中的最低添加量以及在不同加工条件下所制备凝胶油的加工特性。添加量达到0.8%~1.0%(m/m)时,植物油即可呈现较好的凝胶态。在添加量为10%,搅拌速率为500 r/min,加热温度为125℃条件下所制备的凝胶油具有稳定的加工特性。     

Study of several aspects of a general method for the determination of polycyclic aromatic hydrocarbons in liquid smoke flavourings by gas chromatography-mass spectrometry

The effectiveness of the steps of a general method, which includes alkaline treatment of the samples, extraction, clean-up and analysis, for the determination of polycyclic aromatic hydrocarbons in liquid smoke flavourings and smoked foods have been studied, by using mixtures of pure polycyclic aromatic hydrocarbons and of smoke flavouring compounds. All these products were applied to samples of liquid smoke flavourings in order to test the effectiveness of each step of the method, as well as to investigate its effect on real samples, and thus obtain a suitable procedure for the study of polycyclic aromatic hydrocarbons in liquid smoke flavourings. The alkaline treatment has been proved to be necessary because of its capability for removing some smoke components. Both cyclohexane and dichloromethane are able to extract polycyclic aromatic hydrocarbons with high recovery percentages; however, cyclohexane is more adequate due to its lower ability to extract other smoke flavourings components. It is important to note that the elution sequence of polycyclic aromatic hydrocarbons during the clean-up step is quite different depending on the solvent used to dissolve the extract, which determines the ability of this process to isolate polycyclic aromatic hydrocarbons for their accurate identification and quantification by gas chromatography-mass spectrometry in selected ion monitoring mode. Finally, the PAHs present in a liquid smoke flavouring and their concentrations were determined; it was observed that, despite the different extraction solvents and clean-up procedures used, the results were very similar.     

豆渣石油醚萃取物的FT-IR和GC/MS分析

为了解豆渣中小分子物质的赋存形态,本研究用石油醚作溶剂在索式萃取器中对豆渣进行了萃取,并采用傅里叶转换红外光谱仪(FT-IR)和气相色谱/质谱联用仪(GC/MS)对所得石油醚萃取物进行分析,同时用FT-IR对原料豆渣和萃余残渣也进行了分析。结果表明:实验连续萃取5 h,所得石油醚萃取物为淡黄色油状物,萃取率为10.7%;原料和萃余残渣的红外谱图峰形相近,但各吸收峰的吸收强度有所不同,而石油醚萃取物与原料和萃余残渣的红外谱图有明显的差别;石油醚萃取物中共检测到35种GC/MS可识别小分子有机化合物,主要分为烷烃、烯烃、芳香烃、醛、酸、酯及其它类物质7种类别;其中,酯类化合物相对含量为最多,高达61.79%。该研究在开发豆渣的高附加值利用方面具有重要的基础理论意义。     

Solid-phase extraction clean-up of ciguatoxin-contaminated coral fish extracts for use in the mouse bioassay

Florisil solid-phase extraction (SPE) cartridges were used for purifying ciguatoxin (CTX)-contaminated coral fish extracts, with the aim of removing extracted lipid but retaining optimal level of CTXs in the purified fractions. The CTX-containing fraction (target fraction) in fish ether extract was isolated and purified by eluting through a commercially available Florisil cartridge with hexane–acetone–methanol solvent mixtures of increasing polarity (hexane–acetone (4:1, v/v) < acetone–methanol (7:3, v/v) < 100% methanol). Application of Florisil SPE using acetone–methanol (7:3, v/v) condition facilitated the separation of 4.2 ± 0.4 mg (mean ± standard error of the mean (SEM)) of purified target fraction from 20 mg ether extract with good retention of CTXs. The mouse bioassay was used to demonstrate that the average CTX recovery of the target fraction from CTX-spiked samples was 75.8% ± 3.3%, which was significantly increased by 96.7% ± 15% when compared with CTX recovery from ether extracts (44.8% ± 5.2%) without performing SPE purification. Over 70% of non-target lipids were removed in which no CTX toxicity was found. Moreover, the target fractions of both CTX-spiked and naturally CTX-contaminated samples gave more prominent toxic responses of hypothermia and/or induced more rapid death of the mice. The use of acetone–methanol (7:3, v/v) condition in the elution could significantly improve overall recovery of CTXs, while minimizing the possible interferences of lipid matrix from co-extractants on mice.     

Effect of extraction method and ripening stage on banana peel pigments

Carotenoids are one of the most widespread pigments in nature and can be used as health‐promoting natural food colorants. Banana peel, which is a by‐product of banana processing, contains a range of bioactive compounds including carotenoids. There is no published research on the extraction of food‐grade carotenoids from banana peels. This study evaluated the change in the banana peel carotenoid content over its ripening stages and determined the best possible solvent to extract carotenoid for food applications. The solvents permitted under Food Standard Australia New Zealand were used in the study. Ripeness stage 5 contained the highest content of total carotene at 1.86 μg g^?1 of banana peel. From one gram of banana peel, 0.57 μg of xanthophyll and 0.84 μg of beta‐carotene were extracted from ripening stage 5 with a solvent combination of hexane–diethyl ether–acetone and hexane–diethyl ether, respectively.     

石油醚与乙醚测定含糖类样品中脂肪含量的准确率比较

目的为了提高脂肪提取的准确度,采用石油醚及乙醚对含糖类样品进行提取并比对。方法采用GB/T 5009.6-2003《食品中脂肪测定》第二法对其进行提取。结果结果显示,含糖类样品中脂肪测定时,用乙醚提取后测定的结果比用石油醚提取后测定的结果高。由于水解后的物质,更易溶解在极性相对较高的乙醚中,却不会较好地溶解在石油醚中,因而,乙醚提取脂肪含量偏高,准确度下降。结论实验表明,含糖类样品脂肪测定时,用石油醚测定脂肪的准确度高。     

Recovery of aroma compounds from Zhenjiang aromatic vinegar by supercritical fluid extraction

Zhenjiang aromatic vinegar, which is produced from sticky rice through solid‐state fermentation, is highly prized as one of the four famous China‐style vinegars, owing to its unique flavour. In this study, a method of supercritical fluid extraction (SFE) was used for the first time to recover aroma compounds from Zhenjiang aromatic vinegar. For this purpose, the optimal conditions for the extraction of aroma compounds by SFE were determined as follows: CO₂ flow rate, 25 L h^?1; extraction time, 2 h; extraction pressure, 35 MPa; and extraction temperature, 323 K. Using headspace solid‐phase microextraction‐gas chromatography–mass spectrometry (HS‐SPME‐GC‐MS) analysis, a total of 49 and 44 aroma compounds were identified in Zhenjiang aromatic vinegar and its SFE extract, respectively. Acetic acid, ethyl acetate, furfural, phenethyl alcohol, tetramethyl‐pyrazine, 3‐hydroxybutanone and benzaldehyde were the main aroma compounds in the vinegar and its SFE extract. SFE is a fast and sensitive method to recovery aroma compounds from the vinegar.     

大蒜挥发油对米象成虫的控制作用

采用索氏提取法,分别以乙醚、正已烷作为有机溶剂提取大蒜挥发油,详细研究了其对米象成虫的控制作用。结果表明:两种有机溶剂提取的大蒜挥发油对米象成虫均具有较强的驱避、触杀、抑制和熏蒸作用,尤其是乙醚提取的大蒜挥发油的驱避作用和熏蒸作用效果最为明显。     

功能性米糠油超临界流体萃取工艺的研究

采用超临界流体选择性萃取技术提取功能性米糠油,对影响功能性成分亚油酸提取率的主要因素：萃取压力、温度、时间、物料粒度及夹带剂用量进行研究和分析,利用气相色谱法对萃取物中亚油酸进行定性定量分析。通过正交试验优化萃取工艺条件,当萃取压力35MPa、萃取温度40℃、萃取时间100min、物料粒度0.450mm、乙醇用量8% 时,米糠油提取量为17.53g/100g 米糠,亚油酸提取率为87.24%。米糠油中主要脂肪酸油酸41.52%、亚油酸40.81%。产品风味纯正、色泽橙黄、组织均匀不分层、富含亚油酸,可作为功能性油脂应用。     

GC–MS and GC–olfactometry analysis of aroma compounds in a representative organic aroma extract from cured vanilla (Vanilla planifolia G. Jackson) beans

Volatile compounds from cured vanilla beans were extracted using organic solvents. Sensory analysis showed that the aromatic extract obtained with a pentane/ether (1/1 v/v) solvent mixture provided the extract most representative of vanilla bean flavour. Sixty-five volatiles were identified in a pentane/ether extract by GC–MS analysis. Aromatic acids, aliphatic acids and phenolic compounds were the major volatiles. By GC–O analysis of the pentane/ether extract, 26 odour-active compounds were detected. The compounds guaiacol, 4-methylguaiacol, acetovanillone and vanillyl alcohol, found at much lower concentrations in vanilla beans than vanillin, proved to be as intense as vanillin.