调温和油脂组成对巧克力原料油及其应用性能的影响

研究调温和油脂组成对巧克力油脂（可可脂与全氢化棕榈仁油硬脂混合物）的相容性、巧克力的质构以及在20 ℃贮藏3 个月过程中起霜稳定性的影响。结果表明：可可脂与全氢化棕榈仁油硬脂混合物未调温时随可可脂含量增加有明显的稀释作用,经调温后可可脂含量在30%～50%之间出现明显共晶;巧克力硬度受调温和巧克力油脂相容性影响显著。当巧克力油基中可可脂含量＜50%,巧克力硬度随可可脂增加而降低;当可可脂含量＞50%,经调温巧克力硬度显著增加而未经调温巧克力硬度较为恒定。20 ℃贮藏实验发现：未调温,巧克力可可脂含量越高,起霜越显著;调温后,样品可可脂含量在10%～50%范围内起霜程度降低,当可可脂含量＞50%及纯全氢化棕榈仁油硬脂时,产品得到明显改善而无起霜现象。从巧克力的熔化特性和巧克力表层的脂肪酸组成分析发现,当可可脂含量＞50%时,未调温巧克力引起起霜的机制是不稳定晶体向稳定晶体转化;当可可脂含量≤50%时,引起起霜的机制是可可脂与全氢化棕榈仁油硬脂较差的相容性,导致部分油脂迁移至表面重结晶。     

复配乳化剂对月桂酸型代可可脂巧克力物化性质影响研究

通过制备添加由磷脂、单甘油脂、Span 60两两复配(1∶3/1∶1/3∶1,w/w)月桂酸型代可可脂(CBS)模型巧克力,研究添加复配乳化剂对CBS巧克力物化性质影响。结果表明,复配乳化剂种类和添加量均对CBS巧克力物性产生显著影响;其中,磷脂/Span 60复配添加使巧克力表面WI值增加趋势延缓,具有较好延缓起霜作用。     

香菇、茶叶抗类可可脂巧克力脂霜之形态学研究

用偏光显微镜和扫描电镜在形态学方面就香菇和茶叶抗类可可脂巧克力脂霜进行了研究 ,电镜结果表明 ,香菇和茶叶巧克力的质构呈链状有规则排列 ,而对照样则呈杂乱零星无规则排列。偏光显微结果说明 ,无论是起霜还是未起霜的香菇和茶叶巧克力 ,其晶相均呈有规律的均匀分布 ,而对照样则无规则性可言。在相同的促霜时间内 ,对照样起霜程度比香菇和茶叶巧克力大     

巧克力制品起霜的主要原因

引起巧克力制品起霜的三种主要原因,为可可脂Ⅴ型晶体向Ⅵ型转化;硬脂与可可脂相容程度的特殊性;涂层中央向外层的脂迁移。须根据不同的起霜原由,针对不同的物系,采用不同的方法来抑制或延缓起霜。     

谷氨酸棒状杆菌硫酯酶基因表达对脂肪酸合成的影响

旨在为进一步构建脂肪酸高产菌株奠定基础,通过异源和同源表达,研究了谷氨酸棒状杆菌ATCC13032中硫酯酶的基因(NCgl2365和NCgl0090)对脂肪酸合成的影响。结果表明：硫酯酶的过表达对大肠杆菌和谷氨酸棒状杆菌中脂肪酸的种类和含量都产生了影响;基因NCgl2365在大肠杆菌中过表达后脂肪酸产量增加了37.86%,且促进了饱和脂肪酸C16∶0、C18∶0和不饱和脂肪酸C17∶1和C20∶3的生成,在谷氨酸棒状杆菌中同源表达后脂肪酸产量提高了33.43%,C17∶0相对含量增加了51.82%,而C6∶0、C8∶0、C12∶0、C17∶1、C18∶0、C18∶1和C18∶3的相对含量显著减少;基因NCgl0090在大肠杆菌中过表达后脂肪酸产量增加了58.15%,促进了饱和脂肪酸C14∶0、C16∶0、C18∶0和不饱和脂肪酸C17∶1的生成,而在谷氨酸棒状杆菌中同源表达后脂肪酸产量提高了59.12%,其中C16∶0相对含量增加了40.18%,促进了C10∶0、C14∶0、C14∶1、C15∶0、C16∶1、C18∶2、C20∶1和C21∶0 8种新脂肪酸的合成。综上,基因NCgl2...     

巧克力制品起霜的主要原由

本文介绍了引起巧克力制品起霜的三种主要原因，即可可脂Ｖ型晶体向Ⅵ型转化，硬脂与可可脂相容程度的特殊性；涂层中央向外层的脂迁移。笔者提出要根据不同的起霜原由，针对不同的物系，采用不同的方法来抑制或延缓起霜。     

哈萨克羊不同部位脂肪特性的研究

研究了新疆哈萨克羊不同部位脂肪的组成成分差异。采用气相色谱-质谱法对新疆哈萨克羊的肾周脂、网膜脂以及尾脂的脂肪酸组成及挥发性成分进行了分析。结果表明:在尾脂中共检测出20种脂肪酸,而在肾周脂和网膜脂中均检出17种脂肪酸;其中尾脂的饱和脂肪酸(SFA)含量为49.09%,以棕榈酸(C16∶0)的含量最高;肾周脂中SFA的含量为59.44%;网膜脂中SFA的含量为64.00%;肾周脂和网膜脂中SFA均以硬脂酸(C18∶0)的含量最高。在尾脂中不饱和脂肪酸(UFA)的含量为50.48%,在肾周脂中UFA的含量为38.95%,在网膜脂中UFA的含量为35.15%;不同部位脂肪中UFA均以油酸(C18∶1n-9c)的含量最高。羊脂中的挥发性物质主要由醛类、酯类、醇类和酮类组成。     

芒果脂提高巧克力抗霜性的研究

StOSt是芒果脂的特征成分,也是解决巧克力在炎热和冷链缺乏地区软化和起霜问题的关键成分。然而,在应用中发现StOSt虽提高巧克力的耐热性,却可能加速起霜。本文将芒果脂与可可脂复配,制备巧克力油基,分析其甘油酯、甘油三酯组成和熔化行为,进而研究相应巧克力的抗霜性能。结果表明：芒果脂含StOSt 44.7%、低熔点甘油三酯23.9%、甘油二酯8.3%,其中低熔点甘油三酯和甘油二酯含量均显著高于可可脂;其与可可脂复配所得油基的StOSt/POSt/POP比值接近4.0/2.5/1.0且甘油二酯含量为6%~8%时,可延缓油基从V向VI晶型转换,从而提高了所制备巧克力的抗霜性。本文为类似富含StOSt的油脂在抗霜巧克力中的应用提供科学参考。     

不同乳源新鲜干酪中脂肪酸组成和含量的对比

采用气相色谱-质谱联用(GC-MS)的测定方法,分别对由牦牛乳和荷斯坦牛乳制得的新鲜干酪中脂肪酸的组成和含量进行测定。结果表明:新鲜牦牛乳硬质干酪中检出的脂肪酸种类和总相对含量均少于新鲜荷斯坦牛乳硬质干酪,荷斯坦牛乳硬质干酪中总脂肪酸相对含量是牦牛乳硬质干酪中的1.00倍。两种干酪中,最主要的脂肪酸均为棕榈酸(C16∶0)、9-十八碳烯酸(C18∶1)和硬脂酸(C18∶0),这三种脂肪酸的总和占两种干酪的71%以上。牦牛乳干酪中饱和脂肪酸(SFA)种类比荷斯坦乳干酪多1种,但是相对含量低了1.68%;不饱和脂肪酸(UFA)种类比荷斯坦牛乳干酪少2种,但是相对含量是其1.05倍;单不饱和脂肪酸(MUFA)的种类和相对含量均低于荷斯坦牛乳干酪;多不饱和脂肪酸(PUFA)的种类比荷斯坦牛乳干酪少1种,但相对含量是其2.85倍;短链(SCFA)和长链脂肪酸(LCFA)相对含量分别是荷斯坦牛乳干酪的1.10和1.23倍。综上所述,放牧季节和牧草营养成分影响了乳脂肪酸的组成和含量,从而进一步影响了干酪中的脂肪酸组成和含量。     

母乳脂肪在早产儿体外胃肠道消化特性研究

建立体外模拟早产儿胃肠道消化动态模型，研究母乳脂肪在婴儿胃部和小肠环境的脂解特性。结果表明: 母乳脂肪在早产儿胃部消化速度缓慢，120 min时脂解程度为(7.03±0.15)%，在小肠环境中消化速度较快，120 min时脂解程度达到(37.22±1.43)%。母乳脂肪消化全期脂解产生的游离脂肪酸主要为C18∶ 1n-9、C18∶ 2n-6和C16∶ 0，在小肠阶段释放出的sn-2位甘油单酯的脂肪酸组成主要为C16∶ 0、C14∶ 0、C18∶ 1n-9和C18∶ 2n-6。     

Impact of pre-crystallization process on structure and product properties in dark chocolate

Dark chocolate microstructures with different structure densities, i.e., close-packing of the fat crystal lattice, and homogeneity i.e., evenness and connectivity of the fat crystal network, were created by β_VI-seeding or conventional pre-crystallization with various degrees of temper and were evaluated with respect to storage stability. The structure characterization was conducted by measuring the strength of the cocoa butter crystal network with traction tests combined with DSC melting curves. Subsequent storage stability was evaluated with DigiEye technique for fat bloom development and gravimetrical techniques for fat/moisture migration. The two pre-crystallization processes generated significantly different structures and storage stability. Well-tempered β_VI-seeding resulted in a dense and homogenous chocolate structure directly after solidification, which was optimal in order to retard fat bloom and fat migration. However, a too high structure density generated heterogeneous structures with reduced ability to withstand fat bloom. A lower structure density exhibited optimal resistance against moisture migration.     

Surface structure and composition of fresh and bloomed chocolate analysed using X-ray photoelectron spectroscopy, cryo-scanning electron microscopy and environmental scanning electron microscopy

Bloom on chocolate is an unsightly surface condition resulting in a white, powdery appearance that consumers interpret as a sign of poor quality. Bloom results from incorrect processing or storage. Two innovative methods have been developed, and used in conjunction, to investigate the morphology and composition of bloomed chocolate.Environmental scanning electron microscopy (ESEM) was used to image the morphology of the surface of fresh and bloomed chocolate and to observe the changes in morphology, in real time, during heating and cooling. The nodular morphology of sugar bloom was easily distinguished from the blade like crystals of fat bloom. Surface details for the fat blades indicated an extrusion mechanism during their formation on the chocolate surface.“Cold stage” X-Ray Photoelectron Spectroscopy (XPS) was used to analyse the surface composition of fresh and bloomed samples. The carbon species present in the bloom on poorly tempered chocolate were a combination of CH₂, C-OH, OC-OH and O-C-O groups indicating a mixture of sugar and fat bloom. Conversely the species present on bloomed, well tempered chocolate comprised only CH₂, C-OH, OC-OH indicating the bloom was comprised of fat (from cocoa butter) and no sugar.     

On the porous mesostructure of milk chocolate viewed with atomic force microscopy

The surface structure of commercial milk chocolate is examined using atomic force microscopy. It is shown that its surface topography is complex, comprising a finely mottled, yet irregular texture with most structural elements measuring <3 μm in size. It is also demonstrated that a large number of microscopic pores exists at the surface. The morphology of these pores is highly variable, with observed cavities generally being conical in nature with irregularly shaped openings. Typical pore depths range from 1 to 3 μm and are randomly distributed on the surface of milk chocolate, without any defining features in their vicinity to suggest their existence. In the past, it has been postulated that such pores are opening to channels; these being responsible for liquefied cocoa butter transport and subsequent promotion of fat bloom formation. To shed light on any such relationship, milk chocolate is subjected to multiple (6, 12 and 24) temperature cycles (each from 25 to 27 °C and 25 °C over 2 h). Results show that following many cycles, there is crystal growth around some pores, but that the pores themselves are not appreciably altered. This suggests that, under these experimental conditions, they are not directly involved in bloom mediation or liquefied fat transport in milk chocolate.     

Composition and Structure of Fat Bloom in Untempered Chocolate

It is generally accepted that visual fat bloom is caused by the separation of cocoa butter toward the surface. However, this is not always true for all types of bloom. One type of fat bloom, which can occur due to lack of tempering, has still not been completely elucidated. We performed a compositional and structural study of this type of fat bloom in plain chocolate. More specifically, we performed (1) an investigation of its crystallographic properties, (2) investigation of fat content, (3) analysis of the composition of triacylglycerol (TAG), (4) stereomicroscopic observations, and (5) observation and elemental analysis using a scanning electron microscope with an energy‐dispersive X‐ray spectrometer (SEM‐EDS). In the bloomed chocolate, the fat content in the light brown phase was lower than that in the black phase. Concerning fat composition, the content of sn‐1,3‐saturated acyl, sn‐2‐oleoyl glycerols (Sat‐O‐Sat type TAGs) in the light brown phase was lower. The lower fat content is thought to result in its lighter color. The results of our composition analysis and morphological observations suggest that the mechanism of the bloom generation due to nontempering involves not the separation of fat toward the surface but the crystallization of fat which leads to withdrawal of fat from the vicinity of the growing crystal, leading to differences in fat content.     

Effect of storage temperature on texture,polymorphic structure,bloom formation and sensory attributes of filled dark chocolate

The effects of 18 and 30°C storage temperatures on texture, polymorphic structure, bloom formation and sensory attributes of dark chocolate, stored for 8 weeks were studied. Results showed that storage at 18°C for 8 weeks, significantly retarded changes in filled chocolates; the chocolates were free from bloom during the storage period. In contrast, at 30°C there was an increase in the rate of fat migration and rate of change of C36 and C50, and also a decrease in texture and the polymorph structure in the coating changed to β and β′ polymorphs. However, the chocolates bloomed in the third week of storage (2 cycles). Sensory evaluation indicated that, storage at 18°C is better than 30°C, and desiccated coconut gives a pleasant flavour to the chocolate.     

Controlling fat bloom formation in chocolate – Impact of milk fat on microstructure and fat phase crystallisation

The partial replacement of cocoa butter (CB) with milk fat (MF) strongly influences micro-scale topographic evolution and fat phase crystallisation in milk chocolate. Adding MF reduces the incidence of large surface crystals and the number and diameter of amorphous, welled CB deposits (‘cones’), with a concurrent decrease in initial surface roughness (p < 0.05) and rate of surface coarsening. Presence of MF also slows the solidification of the cones into disorganised crystalline masses. Finally, MF reduces the initial solid fat content, and slows the rate of change in whiteness index, as well as the form V to VI polymorphic transition. Fat crystal growth is accelerated by repeated temperature-cycling (26–29 °C) compared to isothermal conditioning (26 °C). However, cone hardening occurs more rapidly when isothermally-stored. Irrespective of fat composition and storage conditions, fat crystal growth, welling and ultimately fat bloom begin only at specific locations on the chocolate surface, suggesting that chocolate’s microstructural heterogeneity is responsible for distinct surface fat crystallisation pathways.     

TEXTURAL CHANGES IN CHOCOLATE CHARACTERIZED BY INSTRUMENTAL AND SENSORY TECHNIQUES

Cocoa butter has a distinct texture due to unique interactions of polymorphic lipid structures. Part of chocolate's appeal is smooth mouthfeel; as fat or sugar bloom forms, textural change is perceived. Correlation of instrumental and sensory texture analysis has not been conducted in stored chocolate. The objective of this study was to analyze texture and color of dark and milk chocolate stored under conditions leading to fat and/or sugar bloom by instrumental and sensory measurements. Milk and dark chocolate was stored 5 weeks at various temperatures and relative humidity (RH), followed by instrumental and sensory texture analysis. All attributes, except springiness, were significantly affected by treatments. According to partial least squares linear regression, instrumental hardness, cohesiveness, chewiness and gumminess modeled sensory hardness. The 30.0C incubator experienced temperature fluctuations, resulting in severe fat bloom. Temperature fluctuations during storage had more influence on texture perception than storage at high temperatures or high RH.

PRACTICAL APPLICATIONS

This research serves as an initial study on textural aspects of chocolate quality upon storage that is the first report to correlate instrumental textural analysis of chocolate to sensory evaluation. Storage temperature and humidity of chocolate greatly impacts consumer texture perception, which is valuable information to small chocolate handlers and manufacturers who have noted to us that many of the larger companies may have this information – but it is not widely available. It also sets the stage for more detailed studies on texture and flavor of chocolate during storage. Although many storage studies on chocolate exist, those that intertwine studies of quality from both an instrumental and a sensory standpoint are lacking.     

几种巧克力调温过程中的结晶特性研究

本文用X-衍射法（XRD）和差示扫描量热法（DSC）对香菇巧克力（LC）,茶叶巧克力（TC）和对照样巧克力（CC）在调温工艺过程中的结晶特性进行了研究,发现3种巧克力在调温过程中的结晶行为各有其特性,这些特性在X-衍射（XRD）谱图中和热差法（DSC）熔解曲线上得到明显反映,LC和CC有相似的变化趋势,3种巧克力在浇模时所形成的晶相之熔点各不相同,LC为29.62℃,TC为21.93℃。CC为26.05℃,促霜试验表明：香菇和茶叶均有较好的延霜效果,其中香菇效果优于茶叶。     

巧克力“白霜”的解决方案

<正>巧克力风味独特、口感好,颇受人们的喜爱。随着巧克力制品消费量的增加,其质量问题也越来越受到各方的关注。其中巧克力起白霜是巧克力产业的世界性难题。白霜花是指加工、贮存、销售过程中,巧克力表面均一发白(酷似秋霜)或起凹凸不平的花斑点,甚至全部变成灰白色而失去光泽。外观使顾客误以为发霉而令人难以接受。严重时,内部组织呈干砂粒状,失去坚脆、断而有声、入口即化,凉爽润滑、细腻而不糊口等特征, 食似嚼蜡,失去商品价值。     

Automated image analysis tool for migration fat bloom evaluation of chocolate coated food products

Migration fat bloom remains a major problem in the production of coated confectionary products where a layer of chocolate is added around a filling or other fat containing substrate. Fat bloom quantification is typically done by a human panel scoring samples in time using a low resolution discrete scale. In view of developing a mechanistic model for migration fat bloom, it is important to have a higher resolution. In this paper, a new, high resolution quantitative method based on image analysis is developed. The method is able to detect both the evolution of fat bloom in terms of the disappearance of gloss and the development of “whitish” portions at the chocolate surface. It was successfully applied to distinguish the difference in fat bloom development rate between samples containing different fat concentrations (0, 3 and 6g/100g) coated on fillings containing different amounts of fat (25 and 75g/100g). In the 25g/100g filling fat case, blooming occurred at a very late stage and was caused by the disappearance of gloss. In the 75g/100g filling fat case the development of a “whitish” surface was responsible for the change in acceptability. The newly developed image analysis method is a solid alternative for the panel procedure.