Influence of oil droplet size on the oxidative stability of the free and encapsulated fractions of freeze-dried microencapsulated sunflower oil

The effect of oil droplet size (ODS) on the oxidative stability (OS) of dried microencapsulated oils has been scarcely studied, and results are contradictory. A few studies have shown increased OS when the ODS was reduced and this was attributed to a decrease in the surface oil content (SOC). Yet, in such studies, only the total oil fraction was evaluated. In the present work, the free (FO) and encapsulated oil (EO) fractions of freeze-dried microencapsulated sunflower oil were analysed to study the effect of changes in the ODS by using different homogenisation pressure (15 or 70 MPa) in the emulsification step. The OS of both the free and encapsulated fractions increased when the ODS was significantly reduced in two samples with different encapsulation matrix, namely caseinate/lactose and maltodextrin/sucrose/gelatine. A reduction in the SOC would explain the increased stability of the FO, but not that of the EO. An additional protective role of the interfacial film could have been involved. In conclusion, if the encapsulation matrix and the interfacial region are effective as oxygen barriers, a reduction in the ODS of the parent emulsion by an increase in the homogenisation pressure will result in capsules more stable against lipid oxidation.     

Influence of relative humidity on oxidation of the free and encapsulated oil fractions in freeze-dried microencapsulated oils

The objective of this work was to evaluate the effect of relative humidity (RH) on oxidation of the free and encapsulated oil fractions of dried microencapsulated oils (DMOs) during long-term storage at 30 °C. Sunflower and fish oils with different tocopherol content were encapsulated in a milk-based encapsulation matrix. The total non-volatile oxidation products and tocopherol were quantitated. Results showed that 0% and 32% RH were, respectively, the most unfavourable and favourable conditions against lipid oxidation. The 32% RH atmosphere exerted a great protective effect on the free oil as compared to 0% RH, while no or a negligible effect was found in the encapsulated oil. Except for the samples most susceptible to oxidation, the free oil remarkably oxidized more slowly than the encapsulated oil regardless of RH. Therefore, there were factors other than moisture that determined the oxidation rate in the free and encapsulated fractions of the DMOs.     

Encapsulation efficiency and oxidative stability of flaxseed oil microencapsulated by spray drying using different combinations of wall materials

This study aimed at evaluating the potential of maltodextrin combination with different wall materials in the microencapsulation of flaxseed oil by spray drying, in order to maximize encapsulation efficiency and minimize lipid oxidation. Maltodextrin (MD) was mixed with gum Arabic (GA), whey protein concentrate (WPC) or two types of modified starch (Hi-Cap 100^TM and Capsul TA®) at a 25:75 ratio. The feed emulsions used for particle production were characterized for stability, viscosity and droplet size. The best encapsulation efficiency was obtained for MD:Hi-Cap followed by the MD:Capsul combination, while the lowest encapsulation efficiency was obtained for MD:WPC, which also showed poorer emulsion stability. Particles were hollow, with the active material embedded in the wall material matrix, and had no apparent cracks or fissures. During the oxidative stability study, MD:WPC combination was the wall material that best protected the active material against lipid oxidation.     

Process engineering parameters and type of n-octenylsuccinate-derivatised starch affect oxidative stability of microencapsulated long chain polyunsaturated fatty acids

Aim of the present study was to investigate the impact of the emulsifying carrier matrix constituent, n-octenylsuccinate-derivatised (OSA)-starch, and process conditions on physical characteristics and oxidative stability of microencapsulated fish oil. Furthermore, the effect of the drying medium, i.e. air or nitrogen, on lipid oxidation during spray-drying and subsequent storage was investigated. Particle characteristics and lipid oxidation of microencapsulated fish oil were both influenced by the type of OSA-starch and the drying conditions. The highest oxidative stability was observed for fish oil microencapsulated in OSA-starch with the lowest average molecular weight and glucose syrup spray-dried at a moderate temperature setting. Particle characteristics of the microcapsules were not attributable for differences in lipid oxidation during storage. In spray-dried carrier matrix particles, the particle size increased with increasing average molecular weight of the OSA-starch and was attributed to an increase in air inclusion. Thus differences in lipid oxidation of the microencapsulated fish oil were attributed to differences in air inclusion as affected by the type of OSA-starch. In terms of spray-drying under inert conditions and in the presence of air, lipid oxidation of microencapsulated fish oil was rather attributed to oxygen availability in the feed emulsion than in the drying gas.     

Effect of total solids content in feed emulsion on the physical properties and oxidative stability of microencapsulated kenaf seed oil

Kenaf (Hibiscus cannabinus L.) seed oil has high potential to be used as edible oil. Despite the high content of polyunsaturated fatty acids, one of the major complications in commercialisation kenaf seed oil is its rapid oxidation, which leads to the production of undesirable toxic substances such as peroxides. The objective of this study was to investigate the effect of total solids content (TSC) on the oxidative stability of microencapsulated kenaf seed oil (MKSO) and to compare its oxidative stability with bulk kenaf seed oil upon accelerated storage. Microcapsules with 20%, 30% and 40% total solids content were prepared. Physical properties, such as the emulsion characteristics and microcapsules characteristics were also studied. Results showed that bulk kenaf seed oil was oxidised to a greater extent compared to the microencapsulated samples. The results showed that 40% total solids content microcapsules had the lowest peroxide value (PV), p-anisidine value (AnV), total oxidation (TOTOX) value and free fatty acid (FFA) value, which were 3.70 ± 0.83 meq O₂/kg oil, 16.12 ± 0.19, 23.52 ± 1.67 and 2.54 ± 0.06%, respectively. The microencapsulation of kenaf seed oil showed protective effect against lipid oxidation.     

葵花籽油的氧化稳定性研究

以葵花籽油的酸值和过氧化值为评价指标,考察了温度、光照、金属离子、氧气、水分对葵花籽油氧化稳定性的影响。结果表明：温度、光照、金属离子、氧气、水分均会引起储藏过程中葵花籽油的酸值和过氧化值的升高,且温度和水分影响较明显;40℃下试样放置24 d后的酸值和过氧化值分别达到1.03 mgKOH/g和19.2 meq/kg;Cu2＋对于葵花籽油过氧化值的影响大于Fe2＋;氧气短期内不会促进葵花籽油酸值的上升;添加了1%和2%水分的葵花籽油的酸值相差不大,均大于未加水样品,且水分含量越高,过氧化值增加越快。     

粉末亚麻油的制备研究

以多孔淀粉为载体,玉米醇溶蛋白为壁材,采用旋转锅喷雾包埋法制备粉末亚麻油。结果表明,多孔淀粉吸附亚麻油颗粒与壁材10%玉米醇溶蛋白液的重量比为1.0∶1.5,增塑剂油酸用量3%(以10%玉米醇溶蛋白液为基准),并分次逐渐喷入包埋剂,在70~80℃条件下热风干燥,制得的粉末亚麻油包埋率为95%,产品具有抗氧化、无异味、耐储存、使用方便等优点。     

微胶囊化方法对紫苏油包埋性能的比较研究

以低粘度辛烯基琥珀酸淀粉酯为壁材,采用喷雾干燥法和冷冻干燥法制备紫苏油微胶囊。通过对固形物含量、芯壁比、均质时间、均质速度及乳化温度的研究,确定了最佳的制备工艺条件为:固形物含量30%,芯壁比1∶4(m/m),在50℃的乳化温度下以16000r/min的速度均质2min。比较研究了两种包埋方法对微胶囊化产品的包埋率、贮藏稳定性、感官及表面形态的影响。喷雾干燥法制备的紫苏油微胶囊化效率(MEE)可达98.86%,而冷冻干燥可达76.24%。喷雾干燥粉呈较规则的球形,流动性好,质地细腻,易溶解;表面光滑,结构致密,减少了与外界环境接触的机会,减慢了氧化速度,能有效延长贮藏期。冷冻干燥粉则疏松多孔,呈现不规则的块状,流动性差,水分含量高。结果表明,喷雾干燥法制备的紫苏油微胶囊的性能优于冷冻干燥法制备的微胶囊产品,且辛烯基琥珀酸淀粉酯通过喷雾干燥包埋紫苏油对延长贮藏期是可行的。      

芝麻酚对鱼油酸奶品质及氧化稳定性的影响

摘 要：目的 开发含二十二碳六烯酸(docosahexaenoic acid, DHA)鱼油的强化型酸奶，探究芝麻酚对鱼油酸奶品质及氧化稳定性的影响。方法 将含芝麻酚的鱼油乳液应用于发酵酸奶中，通过分析酸奶的感官评价、pH、持水力、质构特性、流变特性、自由基清除活性、脂质氧化产物和DHA保留率的变化，探究芝麻酚对鱼油强化酸奶发酵品质和氧化稳定性的影响。结果 鱼油乳液的添加对酸奶的pH和自由基清除活性无显著性影响，但降低了感官评价、持水力、硬度、4℃恒温粘度、储能模量、损耗模量和4~30℃变温粘度，加速了脂质氧化。芝麻酚的添加未显著改变含鱼油酸奶的pH，增加了感官评价、持水力、硬度、4℃恒温粘度、储能模量、损耗模量和4~30℃变温粘度，提高了自由基清除活性、脂质氧化稳定性和DHA保留率(81.19%)。结论 添加300 μM芝麻酚显著改善鱼油酸奶的品质，并提高了酸奶的抗氧化功效，为DHA酸奶产品的开发提供了理论参考。     

月见草油微胶囊粉末油脂中油脂过氧化值测定之提油方法的研究

为测定月见草油微胶囊粉末油脂中油脂过氧化值,比较了碱性乙醚法、机械研磨法、超声波振荡法提油的优劣,结果表明:碱性乙醚法提油率虽高(94.69%),但测得的POV值与原料油相比偏高很多,明显失真;机械研磨法提油率偏低(40.68%),且不稳定,不宜采用;超声波振荡法提油率居中(59.63%),重现性好,精确度高,POV测定值与原料油最接近;试验还表明超声振荡时间以3min为宜。     

焙烤时间对椰子油品质及氧化稳定性的影响

本研究以椰子片为原料,探究焙烤对椰子中油脂的理化性质、脂肪酸组成、结构及氧化动力学的影响。结果表明,在200℃下椰子片经过200～220 s的焙烤,所提取椰子油的品质未发生明显改变,脂肪酸组成和含量无显著变化,仅有少量氧化产物生成。氧化动力学研究结果表明,焙烤后椰子油的氧化诱导期(IP)增加,氧化反应表观活化能(E_a)、活化焓(ΔH)和活化熵(ΔS)都明显增大,说明焙烤处理增加了椰子油的氧化稳定性,这可能与焙烤过程中产生的美拉德产物有关。     

不同抗氧化剂对花生油和大豆油氧化稳定性及预测货架期的影响

在一级压榨浓香花生油和三级大豆油中分别添加油质量0. 02%的叔丁基对二苯酚(TBHQ)(纯度≥99. 0%)、茶多酚(纯度≥95. 0%)、迷迭香提取物(鼠尾草酸含量≥20. 0%)、维生素E(纯度≥90. 0%)等抗氧化剂,采用Schaal烘箱法加速油脂氧化,以过氧化值、酸价、维生素E和甾醇含量为考察指标,研究不同抗氧化剂对一级压榨浓香花生油和三级大豆油氧化稳定性及预测货架期的影响。结果表明,若以过氧化值达到相应国标限量(一级压榨花生油6. 0 mmol/kg、三级大豆油9. 85 mmol/kg)作为评价指标,空白花生油及添加TBHQ、茶多酚、迷迭香提取物、维生素E的花生油预测货架期分别为55. 7、229. 3、161. 6、161. 0、56. 5 d,对应大豆油的预测货架期分别为144、408、112、152、108. 8 d;在预测货架期内,5种花生油中甾醇和维生素E的平均损失率分别为不超过3%和12%,5种大豆油中甾醇和维生素E的平均损失率分别为不超过4%和11%。4种抗氧化剂在浓香花生油中的抗氧化效果为TBHQ茶多酚迷迭香提取物维生素E,在大豆油中的抗氧化效果为TBHQ迷迭香提取物茶多酚维生素E。     

复凝聚法紫苏油微胶囊的制备及其性能研究

为了提高紫苏油的稳定性,采用大豆分离蛋白(SPI)/海藻酸钠(SA)复合凝聚法对紫苏油进行了包埋。考察了乳化剂添加量、均质时间、均质速度、壁材质量比、芯壁质量比等因素对微胶囊性质的影响。并采用正交实验确定其最佳工艺为:乳化剂添加量0.1%,均质速度1000r/min,均质时间1min,凝聚反应p H3.5,壁材浓度3%,SPI与SA质量比4∶1,芯壁质量比1∶1。并比较研究了喷雾干燥和冷冻干燥两种干燥工艺所得产品的包埋率、溶解度、贮藏稳定性等指标。结果表明冷冻干燥制备的紫苏油微胶囊产品包埋率高,稳定性更好。      

天然抗氧化剂对亚麻籽甘油二酯油氧化稳定性的影响

为提高亚麻籽甘油二酯油的氧化稳定性,研究了抗坏血酸棕榈酸酯、迷迭香提取物和维生素E及其组合对亚麻籽甘油二酯油的抗氧化作用。以氧化诱导时间为响应值,在单因素实验基础上,通过响应面分析确定最优的抗氧化剂组合。考察了优化的抗氧化剂组合对亚麻籽甘油二酯油高温加热时反式脂肪酸含量的影响。结果表明：相较于单一的维生素E、迷迭香提取物和抗坏血酸棕榈酸酯,三者组合能显著提高亚麻籽甘油二酯油的氧化稳定性;最优抗氧化剂组合为抗坏血酸棕榈酸酯添加量84 mg/kg、迷迭香提取物添加量405 mg/kg、维生素E添加量1 808 mg/kg,在此条件下亚麻籽甘油二酯油的氧化诱导时间为11.13 h,是空白对照的6.79倍;该抗氧化剂组合能抑制油中反式脂肪酸的生成。天然抗氧化剂绿色、安全,可有效提高亚麻籽甘油二酯油的氧化稳定性。     

不同相对湿度下微胶囊化甜橙油释放的研究

对采用β-环糊精法和乳化喷雾干燥法所制备微胶囊化甜橙油在温度50℃,相对湿度32%、50%和75%下的释放进行研究,并利用Avrami's公式分析不同贮存条件下微胶囊化甜橙油的释放。结果表明:微胶囊化产品在RH=75%贮存条件下的释放要明显快于其它两种贮存条件;在相同的湿度贮存条件下,采用乳化喷雾干燥法制备的微胶囊化甜橙油的释放速度高于采用β-环糊精法所制备的产品。     

Microencapsulation of fish oil by freeze-drying techniques and influence of process parameters on oxidative stability during storage

Dried microencapsulated fish oils (DMFO) were obtained by freeze-drying and the influence of various process parameters on oxidative stability was evaluated. Standard emulsions were composed of sandeel oil, sodium caseinate and lactose, homogenised by three passes at 40 MPa, frozen at −40°C, kept at −30°C and freeze-dried. In selected trials, carbohydrate, homogenisation pressure, freezing rate and initial temperature for freeze-drying were varied. DMFOs were stored at 25°C in the dark and oxidation monitored through anisidine values and polymer levels. Results showed no apparent relationships between oil globule size or microencapsulation efficiency and storage stability, and the only trial with significantly longer shelf-life involved fast-freezing in liquid nitrogen. Received: 24 November 1999     

Microencapsulation of fish oil by spray drying--impact on oxidative stability. Part 1

The aim of this study was to investigate the influence of spray drying on oxidative stability of dried microencapsulated fish oil (DMFO) coated with modified cellulose. DMFO samples were obtained by spray drying of prepared emulsions consisted of water solution of modified cellulose and fish oil. Appearance and size of particles were measured by electron microscopy and laser light microsizer. The oxidative stability of samples was evaluated by peroxide value measurements. Additionally the influence of different antioxidant substances on oxidative stability of the fish oil was investigated. It was observed that oxidation changes were much slower in bulk fish oil compared to DMFO. The most important factor determining shelf-life of the product was the access to air. It can be concluded, that the production of fish oil microcapsules by spray drying technique is possible, however its oxidative stability is not improved.     

耐酸型微胶囊粉末油脂的研制及其性能研究

在对乳化剂品种、用量进行深入研究的基础上,采用喷雾干燥法制备了耐酸型粉末油脂,并对其性能进行了研究。结果表明,用此法可以得到耐酸性很强的微胶囊粉末油脂。复合乳化剂Lc含量下降,制备的产品性能下降,乳化剂Lc对产品的性能影响很大。随着复合乳化剂TH的加入,产品的性能有所回升,复合乳化剂TH对产品性能的改善也会有作用。     

Physical and nutritional properties of baby food containing menhaden oil (Brevoortia tyrannus) and microencapsulated menhaden oil

Purified menhaden oil (PMO) was characterized and microencapsulated. Baby foods containing PMO and microencapsulated purified menhaden oil (MPMO) were evaluated and compared. PMO had higher total omega-3, total saturated, total monounsaturated, DHA, and EPA contents than MPMO. Emulsion containing PMO (EPMO) exhibited viscoelastic characteristic and droplet size of EPMO was around 2-10 μm. The DHA and EPA in the PMO were reduced in MPMO. All baby-food samples with added fish oils had similar FFA values and color. DHA and EPA of baby food were significantly increased by adding PMO and/or MPMO. Total percent values for omega-3 fatty acids of extracted fat from commercial baby food (CB), commercial baby food containing PMO (BPMO), and commercial baby food containing MPMO (BMPMO) were 4.5, 9.8 and 10.1%, respectively.