Precursors of 2-nonenals causing the cardboard off-flavour in butter oil

Methyl linoleate (ML) was autoxidised at room temperature in the dark. In comparison to hexanal, (E)- and (Z)-2-octenal, only very small amounts of (E)-2-nonenal were formed, indicating that linoleic acid was not an important precursor of the latter aldehyde. Palmitoleic acid in form of its methyl ester (MP) was studied as an alternative. Aroma extract dilution analysis revealed (E)-2-nonenal followed by (E)-2-octanal and (Z)-2-nonenal as the most potent odorants of autoxidised MP. Accordingly, in a butter oil sample in which the concentrations of either palmitoleic acid or linoleic acid were doubled, (E)-2-nonenal increased for 73 percent after addition of MP but only for 10 percent after that of ML. This difference indicates that the cardboard off-flavour of butter oil is mainly caused by an autoxidation of palmitoleic acid.     

Furan fatty acids in butter and butter oil

Summary Nine furan fatty acids (F-acids), among which 12,15-epoxy-13,14-dimethyleicosa-12,14-dienoic acid and 10,13-epoxy-11,12-dimethyloctadeca-10,12-dienoic acid predominated, were detected in butter and butter oil. The total amount of the F-acids in four butter samples varied between 116 and 476 mg/kg.

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Furanfettsäuren in Butter und Butterschmalz

Zusammensetzung Neun Furanfettsäuren (F-Säuren), unter denen die 12, 15-Epoxy-13,14-dimethyleicosa-12, 14-diensäure und die 10,13-Epoxy-11,12-dimethyloctadeca-10,12-diensäure dominierten, wurden in Butter und Butterschmalz nachgewiesen. In vier Butterproben variierte der Gehalt der F-Säuren zwischen 116 und 476 mg/kg.

     

葡萄酒微生物污染形成的不良风味物质研究进展

葡萄酒中不良风味物质的存在严重影响葡萄酒的品质,给生产带来较大的经济损失。对葡萄酒生产过程中由于微生物污染而形成的不良风味物质及主要预防措施进行主要介绍,包括葡萄原料被霉菌污染产生的蘑菇味和泥土味等物质;葡萄酒被酒香酵母污染产生的马厩味、酚味和鼠味等物质,被乳酸菌污染产生的黄油味、饭馊味和老鹳草味等物质,被醋酸菌污染产生的胶水味、煮苹果味和醋酸味等物质;橡木桶和软木塞被真菌污染产生的霉味、木塞味等物质。通过对微生物污染产生的不良风味物质特征及其主要防治措施进行系统梳理,为葡萄酒酿造生产提供借鉴。     

Effect of cocoa butter structure on oil migration

Oil migration from a high oil content filling into adjacent chocolate causes changes in product quality. The objective of this study was to quantify the oil migration from a cream filling system into cocoa butter, which provided a model for the behavior of chocolate-enrobed confectionery products with a soft, creamy center. Magnetic resonance imaging (MRI) was used to monitor spatial and temporal changes of liquid lipid content. A multislice spin echo pulse sequence was used to acquire images with a 7.8 ms echo time and a 200 ms repetition time using a 1.03 T Aspect Imaging MRI spectrometer. Samples were prepared as a 2-layer model system of cocoa butter and model cream filling. Three methods were used to prepare the cocoa butter: static, seeded, and sheared. Samples were stored at 25 °C for a time frame of 56 d. The rate of oil migration was quantified by a kinetic expression based on the linear dependence of oil uptake by cocoa butter and the square root of the time. Samples showed distinctly different rates of oil migration, as evidenced by quantitative differences in the kinetic rate constant. Practical Application: This work will be helpful to elucidate the influence of crystallization process and structural properties such as crystal nanostructure and crystal habit on the migration of oil through a crystalline fat matrix.     

制备类可可脂原料用油的研究进展

近年来,巧克力市场逐年壮大,可可脂的需求也随之不断增加。而可可脂产量有限,加之成本较高,可可脂替代品成为学者和商家研究的热点。其中,类可可脂以其特有的优势,成为可可脂替代品中独具特色的一种。对制备类可可脂的原料用油进行了归纳总结,分别从类可可脂的制备方法、原料油脂组成及其相关研究方面对原料油脂进行了概述,从而加深对类可可脂的了解。     

Butter and butter oil classification by PTR-MS

The potential of proton transfer reaction mass spectrometry (PTR-MS) as a tool for classification of milk fats was evaluated in relation to quality and authentication issues. Butters and butter oils were subjected to heat and off-flavouring treatments in order to create sensorially defective samples. The effect of the treatments was evaluated by means of PTR-MS analysis, sensory analysis and classical chemical analysis. Subsequently, partial least square-discriminant analysis models (PLS-DA) were fitted to predict the matrix (butter/butter oil) and the sensory grades of the samples from their PTR-MS data. Using a 10-fold cross-validation scheme, 84% of the samples were successfully classified into butter and butter oil classes. Regarding sensory quality, 89% of the samples were correctly classified. As the milk fats were fairly successfully classified by the combination of PTR-MS and PLS-DA, this combination seems a promising approach with potential applications in quality control and control of regulations.     

Volatile off-flavour compounds in desiccated coconut

Aliphatic methyl ketones and secondary alcohols have been isolated from desiccated coconut and shown to be responsible for the rancid off-flavour. Two series of compounds have been isolated. The series with an odd number of carbon atoms (C_5,7,9,11) comprising pentan-2-one, pentan-2-ol, heptan-2-one, heptan-2-ol, nonan-2-one, nonan-2-ol and undecan-2-one is derived from even chain fatty acids one carbon atom longer, present in the coconut oil by a modified β-oxidation due to growth of moulds. Heptan-2-one and nonan-2-one were present in the greatest concentration in the rancid coconut. These compounds gave an odour reminiscent of rancid almonds and turpentine respectively while heptan-2-ol and nonan-2-ol gave an odour similar to rancid coconut as well as a musty, stale odour. This type of off-flavour has been called ketonic rancidity and is an oxidative variation of the hydrolytic type of rancidity. The presence and origin of the even numbered series (C_6,8), hexan-2-one, hexan-2-ol and octan-2-one is discussed. The increase in C_5,6,7,8,9,11 oxidation products in the rancid samples occurred at the expense of C_8,10,12 short chain fatty acids.     

Lipase production by lactic acid bacteria and activity on butter oil

Over 100 different lactic acid bacteria representing the genera,Lactobacillus, Lactococcus, Leuconostoc, PediococcusandStreptococcus, were screened for lipase production using an agar medium containing rhodamine b and three different lipid substrates, triolein (C18:1), tributyrin (C4:0), and butter oil. A total of 29 lipase-producing strains were identified. Assays using extracellular material (supernatant) and intracellular extracts (prepared by sonication) showed that lipases were produced as intracellular enzymes in the strains studied. Several different lipase assays were employed to measure lipase activities of lipases produced by selected lactic acid bacteria. The best lipase assay was the pH stat titrator, which gave quick, quantitative results of lipase activity toward a number of synthetic triacylglyceride substrates, as well as natural substrates, such as butter oil. Activities for cell free extracts ranged from <1.0–55 μmol free fatty acid released per minute per milligram of protein. However, lipase activities of extracts obtained from lactic acid bacteria were substantially lower than those reported for other micro-organisms, such asPseudomonasspp. andCandidaspp. Studies on the substrate specificity of selected lipases indicated the lipases were generally operating in a random fashion with regard to fatty acid type, although there was a slight preference for oleic acid.     

Fractionation of buffalo butter oil by supercritical carbon dioxide

Buffalo butter oil was fractionated by supercritical carbon dioxide into four fractions (F₁-F₄). Fractionation was performed at 50 and 70 °C over a pressure range of 10.9-40.1 MPa. Short chain fatty acids (C₄-C₈), medium chain fatty acids (C₁₀-C₁₄) and saturated fatty acids were decreased from F₁ to F₄, while long chain fatty acids (C₁₆-C_18:3) and unsaturated fatty acids were increased. Triacylglycerol molecular species exhibited a similar trend as fatty acids. Cholesterol was concentrated in F₁, and with increasing the fluid density, it decreased by more than 50% in F₄. Substantial changes occurred in the chemical composition of the fractions led to distinctive differences in their thermal profile and solid fat content. Fractions obtained in the initial stages of the fractionation exhibited lower melting behavior that obtained in the late stages.     

Oxidative stability of fish oil blended with butter.

The oxidative stability of fish oil blended with milk products was evaluated. Oxidation of the oil blend was determined by peroxide value and rancimat test. Improved oxidative stability was observed for fish oil blended with butter. Unsalted and salted butters showed no difference in improvement of effect on oxidative stability of fish oil. No influence on oxidative stability for the fish oil was observed with butter oil, which was the oil fraction of butter. These studies suggested that the improved oxidative stability of fish oil-butter blend was due to the hydrophilic fraction of butter and that butter could improve the oxidative stability of polyunsaturated oils such as fish oil.     

Monoacylglycerols derived from butter oil by Penicillium roquefortii in suspension cultures

Structural isomers of monoacylglycerols (monoglycerides, MAGs) were identified and compared after degradation of butter oil by two strains of Penicillium roquefortii and a commercial lipase from P roquefortii (EC 3.1.1.3) at pH 7.0 and 10 °C. The conditions were selected as they were comparable with those used in the manufacture of blue mould‐ripened cheese. The commercial lipase was selected to compare with the fungal strains in terms of acyl migration. Results showed that the main isomers formed by lipolysis with the commercial lipase were sn‐2 MAGs (64 mol%), whilst spores and emerging mycelia of P roquefortii produced mainly sn‐1(3) MAGs (83–90 mol%). The work reported here may lead to further assessment of different MAG structural isomers as natural preservatives in foods and dairy products. © 2002 Society of Chemical Industry     

Digestive lipolysis in the preruminant calf. The abomasal hydrolysis of butter oil, coconut oil, palm oil and tallow

The effect of intramolecular short-chain fatty acids on the abomasal hydrolysis of long chain acyl ester bonds has been examined using four different fats. An evaluation of abomasal infusion of feeds as a technique to avoid hydrolysis of fat by salivary lipase has been made. Only calves considered to be typically functional preruminants were used for the investigations. Five preruminant calves each received five experimental milk feeds consisting of skim milk plus 3% of either butter oil, coconut oil, palm oil or tallow. All feeds were given by mouth but the feed that contained butter oil was also introduced directly into the abomasum via a simple cannula. In all cases, digesta leaving the abomasum were continuously sampled for 12 h via a re-entrant cannula in the proximal duodenum, anterior to the entry of the bile and pancreatic ducts. Butter oil given by mouth was hydrolysed to a greater extent than the other fats. This was due not only to the ease of liberation of the short chain fatty acids, but also to an enhanced liberation of longer chain acids when short chain acids are present in the triglyceride. Butter oil introduced directly into the abomasum of truly preruminant calves was not hydrolysed, suggesting that by using this technique studies could be made in vivo of the hydrolysis of fat by pancreatic lipase alone.     

香蕉粉及香蕉花生酱的加工工艺研究

该试验以香蕉和花生为原料对香蕉的护色、干燥方法及香蕉花生酱的加工工艺进行了研究。试验结果表明:香蕉去皮后,用0.2%柠檬酸 0.01%维生素C溶液浸泡10min护色、打浆,在75℃下热风干燥60min,得到香蕉粉,香蕉花生酱的最佳配方为花生酱73%、香蕉粉15%、单甘酯2%、蔗糖5%、植物油5%;香蕉花生酱适宜的杀菌条件为121℃,16min。     

可可脂在非等温条件下结晶及融化特性的研究

采用差式扫描量热仪(DSC)研究了升降温速率和乳化剂对可可脂非等温结晶和融化过程中晶体衍变过程的影响。结果显示:可可脂结晶和融化过程都对温度变化速率(λ)敏感,随λ的提高,放热峰和吸热峰强度均增大,峰值(Tp)则分别降低和升高;单甘酯促进可可脂组分分离,降低结晶温度,改变晶体的融化特性;卵磷脂则提高可可脂结晶温度,对融化特性不产生影响,添加单甘酯和卵磷脂都使可可脂结晶量增加。      

牛油调和煎炸油的开发及煎炸性能研究

以牛油、高油酸菜籽油和稻米油为基油开发调和煎炸油。通过连续煎炸试验研究了4种调和油的煎炸性能,并与牛油进行对比。结果表明:4种调和油的胆固醇含量为17.48～30.02mg/100 g,远低于牛油的97.35 mg/100 g; 4种调和油的酸价、过氧化值、碘值、土豆条吸油率及氧化稳定性均优于牛油。4种调和油的初始极性组分含量均高于牛油,苯并芘含量也相对牛油较高,但在整个煎炸过程中均低于欧盟规定的最大限值(2μg/kg)。4种调和油煎炸后饱和脂肪酸和单不饱和脂肪酸含量均增加,多不饱和脂肪酸含量均减少。4种调和油的反式脂肪酸含量较牛油低很多。综合分析表明,调和油的煎炸性能相比牛油优势明显,由20%牛油、30%高油酸菜籽油及50%稻米油调和而成的煎炸油综合性能最佳。     

花生酱蛋白饮料复配乳化增稠剂的研究

以花生酱、奶粉、白糖等原辅料制成的花生蛋白饮料为试样,进行不同均质压力、不同乳化增稠剂组合试验,考察其体系的稳定性。结果表明：采用均质温度70℃、均质压力40MPa,添加复配乳化增稠剂0.46%（聚甘油脂肪酸酯0.10%、硬脂酰乳酸钠0.03%、羧甲基纤维素钠0.03%、微晶纤维素0.25%、卡拉胶0.05%）时,产品的稳定效果最好。经常温贮存6个月观察,试样无沉淀,无明显脂肪上浮。     

Enzymatically modified tea seed oil as cocoa butter replacer in dark chocolate

Cocoa butter replacer (CBR) was prepared by enzymatic interesterification of hydrogenated and solid fraction (SF) of tea seed oil at weight percent ratio of 30:70, using sn‐1,3 specific lipase from Thermomyces lanuginosus. Dark chocolate samples were then prepared with the prepared CBR as a replacement for 5%, 10%, 15% and 20% of cocoa butter (CB) and the effect of the replacement on hardness (as a key quality factor in chocolate) of the chocolate samples was investigated. Results showed that chocolate samples containing 5% and 10% of interesterified sample (EIS), had the closer texture to that of CB chocolate than other samples. The solid fat content (SFC) profiles also revealed that blending 10% of EIS with CB in chocolate formulation dose not affect the sharp melting point of CB. Based on the results taken from bloom formation, polymorphic structure and sensory evaluation, adding up to 10% of EIS in chocolate formulation reduces the bloom development without adverse affecting the desirable β crystal formation and sensory qualities in the chocolate samples.