酶法制备甘油二酯与甘油三酯的结晶特性研究

采用Lipozyme RM IM催化大豆油和棕榈油硬脂(熔点45℃)混合油与单甘酯(由大豆油、棕榈油硬脂和甘油合成)酯交换合成甘油二酯,并以此酶催化大豆油和棕榈油硬脂(熔点45℃)酯交换合成甘油三酯。采用差示扫描量热仪、脉冲核磁共振仪和偏光显微镜测定甘油二酯、甘油三酯以及甘油三酯中添加不同比例甘油二酯(10%、30%、50%和70%)的混合物的结晶和熔化性质。结果表明:脂肪酸组成接近的甘油二酯,初始结晶温度(28.14℃)和熔点(48.26℃)比甘油三酯初始结晶温度(8.51℃)和熔点(30.58℃)高。添加50%和70%的甘油二酯能够提高甘油三酯的熔点和初始结晶温度,而添加10%和30%的甘油二酯对其结晶影响较小。随着甘油二酯添加比例的增大,混合物的固体脂肪含量逐渐增加。添加50%和70%甘油二酯的混合物,在熔点温度附近时晶体为针状。     

大豆油与极度氢化棕榈油填充床酯交换法制备人造奶油基料油的中试研究

采用中试填充床反应器(PBR),使用Lipozyme TL IM脂肪酶催化大豆油与极度氢化棕榈油酯交换反应制备人造奶油基料油,通过调节反应器的流速控制反应时间,分别收集5种流速(34、63、87、103、120 m L/min)下制备的酯交换产物。通过脉冲核磁共振(p-NMR)、差示扫描量热仪(DSC)等表征原料油混合物及5种酯交换产品在不同温度下的固体脂肪含量(SFC)、熔融结晶特性等物理化学性质。结果表明:酯交换反应降低了产品中三不饱和甘油三酯(UUU)、三饱和甘油三酯(SSS)的含量,提高了两饱和甘油三酯(SSU)、两不饱和甘油三酯(UUS)的含量;25℃以上,酯交换产品的SFC低于原料油混合物,酯交换产品熔点、结晶起始点相比于原料油混合物熔点(53.81℃)和结晶起始点(37.19℃)均有降低;在103 m L/min流速下(产量约为130 kg/d),酯交换产品的酯交换率可以达到91.32%。研究结果对工业化人造奶油基料油的高效生产有重要借鉴作用。     

脂肪酶催化饱和单甘酯与棕榈油酯交换制备含甘油二酯油及其结晶特性研究

采用脂肪酶Lipozyme TL IM催化饱和单甘酯和棕榈油(24℃)进行酯交换反应,酯交换油脂经分子蒸馏分离纯化得到含28.10%甘油二酯(DAG)油。对比分析了酯交换反应前后油脂的甘油酯组成和脂肪酸组成、热力学性质以及固体脂肪含量(SFC)。结果表明:含DAG油的不饱和脂肪酸含量提高至42.94%,熔点降低至45.4℃,SFC值显著降低;X射线衍射结果表明含DAG油的晶型以β型和β'型为主;偏光显微镜观察结果表明含DAG油的晶体网络结构主要由球状晶体聚集而成,且晶体尺寸变小,固液相分散更均匀;结晶熔化曲线、SFC分布以及结晶特性均表明含DAG油适合用作食品专用油脂基料。     

棕榈油中间分提物PMF在软冰淇淋中的应用

将作为棕榈油分提副产物的棕榈油中间分提物(PMF)应用于软冰淇淋生产,通过对比分析棕榈油分提副产物中6种不同熔点(30~40)℃的PMF与4种代表性市售软冰淇淋预拌粉中油脂的理化性质、脂肪酸组成及固体脂肪含量(SFC)发现,熔点为37.2℃的PMF(PMF-3)在(0~10)℃和(26.7~33.3)℃SFC值变化比较缓慢,而在(10~26.7)℃SFC迅速下降,最适宜应用于软冰淇淋的生产,且其所含饱和脂肪酸与不饱脂肪酸比例接近1:1,主要脂肪酸为棕榈酸和油酸,这种脂肪酸组成使PMF-3较其他食用油具有更好的热稳定性。因此,研究选择PMF-3作为生产软冰淇淋用的油脂。通过L_9(3~4)正交试验,对原料中PMF-3、脱脂乳粉、糖及麦芽糊精含量配比进行优化,结合感官评价分析,发现PMF-3的添加量为8%,脱脂乳粉的添加量为8%,麦芽糊精的添加量为1%,白砂糖的添加量为12%时生产的软冰淇淋硬度最适中,口感最佳。     

棕榈油硬脂和棕榈油中间分提物性能及相容性研究

为改善油脂可塑性和口溶性,及为开发以棕榈油产品为主要原料专用油脂产品提供理论依据,研究棕榈油硬脂(PSt)、棕榈油中间分提物(PMF)两者间相容性。测定二元混合体系固体脂肪含量(SFC)值,并通过计算其理论值与实测值之间差值△SFC,结合T–△SFC曲线、二元等温曲线等直观分析,结果表明:PSt与PMF混合物在25℃、PSt含量为30%～50%时,二者间偏晶现象严重;而在35℃～50℃时,二者间共晶现象较为严重;在0℃～10℃和30℃～35℃范围内,二者间具有较好相容性。     

棕榈油干法分提条件研究

以碘价为54棕榈油为原料,采用干法分提制备棕榈油中间熔点物(POMF)。在单因素试验基础上,采用响应面优化实验,研究结晶温度、冷却速率和养晶时间对干法分提效果影响。得出棕榈油干法分提最佳工艺条件为:结晶温度16.83℃,冷却速率1.31℃/h,养晶时间13.39 h。在此条件下棕榈油中间熔点物(POMF)得率为30.3%,熔点为35.0℃,熔程为32℃³6℃。实验测定结果为:棕榈油中间熔点物(POMF)得率为29.9%,熔点为35.3℃,熔程为32℃36℃。实验测定结果为:棕榈油中间熔点物(POMF)得率为29.9%,熔点为35.3℃,熔程为32℃³6℃。     

国产巧克力球回软问题的研究

为探索国产巧克力球储存后回软的原因,分别采用核磁共振法、气相色谱法和水分活度测定仪法测定巧克力球内外层固体脂肪含量(SFC)、内外层脂肪酸组成以及威化层的水分活度.在不同温度条件下,国产巧克力球外层SFC均低于参照样(40℃除外),且随着储藏时间的延长而降低(＜20℃).内层在较低温度时(＜17℃),随储藏期的延长而降低,而在较高温度时(＞17℃)则呈相反趋势.两者内外层主要脂肪酸含量相当,但反式脂肪酸含量为参照样的1.6倍.另国产巧克力球威化层的水分活度较高,且随着储藏时间的延长逐渐增大.本研究表明,国产巧克力球外层巧克力的固体脂肪在储藏过程中向内层迁移,选料差异以及外涂层的密封性等原因可能共同导致了巧克力球储藏过程中的回软现象.     

单甘酯对棉籽油和棕榈硬脂酯交换体系结晶性质的影响

研究不同油酸单甘酯添加量对棉籽油和棕榈硬脂(质量比50:50)酶催化酯交换产物结晶性质的影响。结果表明:添加2%和5%的油酸甘油酯,酯交换产物的固体脂肪含量(SFC)与熔点基本不发生变化,添加量增大到10%,体系的SFC与熔点略有下降;添加不同量的油酸甘油酯,均使酯交换产物结晶温度发生变化,其中低熔点组分对应的峰温度随添加量增加而增大,高熔点组分对应的峰温度随添加量增大而下降;添加2%的油酸单甘酯对酯交换产物的成核速率和结晶速率不存在影响;添加不同量的油酸单甘酯后,酯交换产物中β′晶形比例下降,下降程度与添加量成负相关。     

基于酶促酯交换的含亚麻酸巧克力的制备及其性质研究

利用固定化脂肪酶Lipozyme TLIM催化质量比为38∶3的天然可可脂与亚麻籽油进行酯交换反应,得到熔点为(36.52±0.34)℃的油脂(称为酯交换可可脂)。酯交换可可脂中亚麻酸的含量由反应前0.64%±0.01%升高至3.10%±0.28%,主要甘三酯POP、POS和SOS的含量由84.52%降至62.72%,低熔点甘三酯UUU和SUU含量分别由0.92%和6.85%增加至10.94%和16.60%。酯交换可可脂的固体脂肪含量(SFC)在5~30℃时低于天然可可脂的SFC,但其随温度变化的趋势与天然可可脂的相一致,当温度高于34℃时,酯交换可可脂的SFC略高于天然可可脂的SFC,37℃时酯交换可可脂的SFC为1.64%。以酯交换可可脂为原料制备的含亚麻酸巧克力表面光滑,口感细腻,具有可可和亚麻籽油独特的香味。加速氧化实验结果表明该巧克力20℃时的货架期为428 d,约61周,具有良好的贮藏稳定性。     

急冷温度及凝胶剂添加量对植物甾醇/谷维素油凝胶物理特性的影响

为促进植物甾醇/谷维素油凝胶在零反式、低饱和的营养型塑性脂肪中的应用,以大豆油为基料油,植物甾醇/谷维素为凝胶剂,在不同急冷温度(5、20℃)及凝胶剂添加量下制备油凝胶,测定不同急冷温度及凝胶剂添加量下植物甾醇/谷维素油凝胶的晶型、晶体形态、物理稳定性、质构和热力学特性的变化。结果表明：随着凝胶剂添加量的升高,油凝胶中晶体排列逐渐致密,硬度增大,熔点升高;尽管急冷温度对油凝胶的晶型(β晶型)没有明显影响,但相对于5℃急冷,20℃急冷得到的油凝胶晶体组装更为致密,物理稳定性增强;在与传统甘三酯固脂对比SFC与硬度和熔点的关系中发现,在油凝胶体系中熔点随SFC的增加呈现非线性关系增长,但低固体脂肪含量(4.85%)即可赋予植物甾醇/谷维素油凝胶较高的硬度。综上,急冷温度及凝胶剂添加量对植物甾醇/谷维素油凝胶的物理特性具有显著的影响。     

棕榈油与猪油在组成结构和功能特性上的比较

比较了3种棕榈油和6种猪油产品在理化指标、营养与功能特性指标以及脂肪酸组成及其在甘油三酯Sn-2位上的分布情况,以判断棕榈油对猪油的可替代性.结果表明,棕榈油和猪油的熔点、碘值、酸值、过氧化值等理化指标很接近;棕榈油不含胆固醇,具有比猪油较高的V_E含量和氧化稳定性;在可塑性方面,精炼棕榈油与猪板油相当,而且好于猪杂油和猪膘油,棕榈硬脂与猪骨油相当,棕榈液油与猪皮油相当;虽然棕榈油和猪油的脂肪酸组成具有相似性,猪油的不饱和脂肪酸含量略高于棕榈油的不饱和脂肪酸含量,但是棕榈油的Sn-2位上主要分布不饱和脂肪酸,而猪油的Sn-2位上主要分布饱和脂肪酸,使棕榈油比猪油更加容易消化吸收.     

CHEMICAL AND PHYSICAL PROPERTIES OF PLASTIC FAT PRODUCTS SOLD IN MALAYSIA

Five domestic and four imported Malaysian plastic fat products and their separated high melting point triacylglycerols (HMG) were analyzed for their chemical and physical characteristics. Chemical characteristics consisted of fatty acid (FA) and triacylglycerol (by TG carbon number) composition. Physical characteristics encompassed dropping and softening points, solid fat content, polymorphic crystal habit and DSC melting and crystallization patterns. β crystal habit was related to high levels of 16 or 18 carbon fatty acids in the HMG and high levels of TG48 or TG54 which are β tending. Domestic products contained very low levels of trans fatty acids; they were blends of natural fats such as palm oil, palm kernel and milk fat. Levels of the individual fats in the blends were estimated by means of FA and TG composition analyses. The content of solid fat, determined by the AOCS method, was much lower than that obtained by the IUPAC method. Texture at 23C of products, as determined by penetrometer test of the original materials, was similar for all products.     

Structured lipids obtained by chemical interesterification of olive oil and palm stearin

Interesterification of palm stearin (PS) with liquid vegetable oils could yield a good solid fat stock that may impart desirable physical properties, because PS is a useful source of vegetable hard fat, providing β′ stable solid fats. Dietary ingestion of olive oil (OO) has been reported to have physiological benefits such as lowering serum cholesterol levels. Fat blends, formulated by binary blends of palm stearin and olive oil in different ratios, were subjected to chemical interesterification with sodium methoxide. The original and interesterified blends were examined for fatty acid and triacylglycerol composition, melting point, solid fat content (SFC) and consistency. Interesterification caused rearrangement of triacylglycerol species, reduction of trisaturated and triunsaturated triacylglycerols content and increase in diunsaturated-monosaturated triacylglycerols of all blends, resulting in lowering of melting point and solid fat content. The incorporation of OO to PS reduced consistency, producing more plastic blends. The mixture and chemical interesterification allowed obtaining fats with various degrees of plasticity, increasing the possibilities for the commercial use of palm stearin and olive oil.     

Properties of high-oleic palm oils derived by fractional crystallization

ABSTRACT:  High-oleic palm oil (HOPO) with an oleic acid content of 59.0% and an iodine value (IV) of 78.2 was crystallized in a 200-kg De Smet crystallizer with a predetermined cooling program and appropriate agitation. The slurry was then fractionated by means of dry fractionation at 4, 8, 10, 12, and 15 °C. The oil and the fractionated products were subjected to physical and chemical analyses, including fatty acid composition, triacylglycerol and diacylglycerol composition, solid fat content, cloud point, slip melting point, and cold stability test. Fractionation at 15 °C resulted in the highest olein yield but with minimal oleic acid content. Due to the enhanced unsaturation of the oil, fractionation at relatively lower crystallization temperature showed a considerable effect on fatty acid composition as well as triacylglycerol and diacylglycerol composition of liquid fractions compared to higher crystallization temperature. The olein and stearin fractionated at 4 °C had the best cold stability at 0 °C and sharper melting profile, respectively.     

Physicochemical characteristics of palm oil and sunflower oil blends fractionated at different temperatures

This research was carried out to determine the effect of fractionation temperature on the physicochemical characteristics of refined, bleached and deodorized (RBD) palm oil and sunflower oil blends fractionated at different temperatures. Blends of 20% and 40% sunflower oil with 80% and 60% RBD palm oil, respectively, were fractionated at three different temperatures (15, 18 and 21 °C). The results showed that olein with higher iodine value was obtained at lower fractionation temperature. This was because, at lower fractionation temperature, more of the polyunsaturated fatty acid, namely linoleic acid (C18:2), went into the liquid fraction. On the other hand, more of the saturated fatty acid, namely palmitic acid (C16:0), went into the liquid fraction at higher fractionation temperature. Blending reduced the triacylglycerol composition, namely POP, POS, SOO and PLP, while OLO, PLL, OLL and LLL/LLnO increased. Lower fractionation temperature decreased the composition of monosaturated triacylglycerol and increased the composition of di- and polyunsaturated triacylglycerols. Lower fractionation temperature produced a liquid fraction with lower solid fat content and lower cloud point than did higher fractionation temperature.     

THE EFFECT OF DIFFERENT TYPES OF STIRRER AND FRACTIONATION TEMPERATURES DURING FRACTIONATION ON THE YIELD, CHARACTERISTICS AND QUALITY OF OLEINS

Refined, bleached and deodorized (RED) palm oil was fractionated by dry fractionation using two different types of stirrer at 3 fractionation temperatures to produce palm olein (POo). Statistical analysis by SAS showed significant differences (P < 0.05) between fractionation temperatures of 15C and 21C, and no significant differences between two types of stirrer on product yield. Iodine value showed significant differences between fractionation temperatures of 15C and 18C, and 15C and 21C but no significant difference was observed between the two types of stirrers. Analysis showed that palm olein fractionated at lower temperature contained less saturated fatty acids, more unsaturated fatty acids and lower solid fat than oleins fractionated at higher temperatures.     

氢氧化钠与甘油催化棕榈基油脂酯交换反应

利用氢氧化钠与甘油催化棕榈液油和棕榈硬脂进行酯交换反应,考察反应温度、氢氧化钠浓度、反应时间、氢氧化钠与甘油比例、搅拌速度对反应产物固体脂肪含量、甘油三酯碳数、酸值、皂化值、熔点的影响。结果表明:在反应温度110℃、反应时间30 min,氢氧化钠浓度0.5%、氢氧化钠与甘油的比例1︰1、搅拌速度150 r/min的条件下,氢氧化钠与甘油混合物的催化效果接近于甲醇钠。     

An investigation on the physicochemical characterization of interesterified blends of fully hydrogenated palm olein and soybean oil

In this study, the effect of interesterification (using sodium methoxide) on physicochemical characteristics of fully hydrogenated palm olein (FHPO)/soybean oil blends (10 ratios) was investigated. Interesterification changed free fatty acid content, decreased oil stability index, solid fat content (SFC) and slip melting point (SMP), and does not affected the peroxide value. With the increase of FHPO ratio, oil stability index, SFC and SMP increased in both the interesterified and non-interesterified blends. Fats with higher FHPO ratio had narrower plastic range, as well. Compared to the initial blends, interesterified fats had wider plastic ranges at lower temperatures. Both the non-interesterified and interesterified blends showed monotectic behavior. The Gompertz function could describe SFC curve (as a function of temperature, saturated fatty acid (SFA) content or both) and SMP (as a function of SFA) of the interesterified fats with high R² and low mean absolute error.     

Enzymatic interesterification of palm and coconut stearin blends

Hard fractions of palm oil and coconut oil, blended in the ratios of 90:10, 85:15, 80:20 and 75:25, were interesterified for 8 h using Lipozyme TL IM. Major fatty acids in the blends were palmitic acid (41.7–48.4%) and oleic acid (26.2–30.8%). Medium‐chain fatty acids accounted for 4.5–13.1% of the blends. After interesterification (IE), slip melting point was found to decrease from 44.8–46.8 °C to 28.5–34.0 °C owing to reduction in solids content at all temperatures. At 37.5 °C, the blends containing 25% coconut stearins had 17.4–19% solids, which reduced to 0.4–1.5% on IE, and the slip melting point (28.6 and 28.8 °C) indicated their suitability as margarine base. The reduction in solid fat index of the interesterified fats is attributed to the decrease in high‐melting triacylglycerols in palm oil (GS₃ and GS₂U type) and increase in triolein (GU₃) content from 1 to 9.2%. Retention of tocopherols and β‐carotene during IE was 76 and 60.1%, respectively, in 75:25 palm stearin and coconut stearin blend.     

Crystallization behavior of milk fat obtained from linseed-fed cows

Milk with an increased content of unsaturated fatty acids was obtained by incorporating 60% of extruded linseed into the concentrate of cows. Two groups of Holstein cows (3 animals/group) were fed a concentrate (control or linseed enriched) together with the same roughage diet (ad libitum). After an adaptation period of 3 wk, evening and morning milk samples were collected every 7 d for 3 wk. Milk was decreamed and anhydrous milk fat (AMF) was isolated from the fat fraction by using the Bureau of Dairy Industries method. The objective of this study was to investigate if the crystallization mechanism of milk fat changed when the content of unsaturated fatty acids was increased. Therefore, the crystallization behavior of a milk fat enriched with unsaturated fatty acids was compared with that of a control milk fat. Nonisothermal crystallization was investigated with differential scanning calorimetry, and 1-step and 2-step isothermal crystallization behaviors were investigated using pulsed nuclear magnetic resonance, differential scanning calorimetry, and x-ray diffraction. A higher content of unsaturated fatty acids in AMF resulted in an increased proportion of low melting triglycerides. These triglycerides lowered the solid fat content profile, particularly at refrigerator temperatures. Furthermore, they induced some changes in the crystallization and melting behaviors of milk fat compared with a control AMF, although no fundamental changes in the crystallization mechanism could be revealed. Even though a lower melting point could be observed for milk fat with a higher content of unsaturated fatty acids, a similar degree of supercooling was needed to initiate crystallization, resulting in a shift in onset temperature of crystallization toward lower temperatures. In addition, slower crystallization kinetics were measured, such as a lower nucleation rate and longer induction times, although crystallization occurred in a similar polymorphic crystal lattice. During melting, a shift in offset temperature toward lower temperatures could be observed for the 3 melting fractions of AMF in addition to a higher proportion of low melting triglycerides. These results demonstrate that a higher content of unsaturated fatty acids has some effect on the crystallization behavior of milk fat. This knowledge could be used to produce dairy products of similar or superior quality compared with conventional products by intervening in the production process of dairy products.