Extractable oil in microcapsules prepared by spray-drying: Localisation,determination and impact on oxidative stability

Aim of the present study was to investigate the localisation of the extractable oil in spray-dried microencapsulated fish oil prepared under different spray-drying conditions and to investigate the impact on lipid oxidation upon storage. Confocal laser scanning microscopy, scanning electron microscopy and different extraction procedures revealed that the extractable oil in microencapsulated fish oil is mainly located on the surface and in oil droplets close to the surface. Consequently, different methods for determination of the different fractions are proposed. Lipid oxidation as determined by hydroperoxide content or anisidine value was higher in microcapsules with 50% oil load spray-dried at 210/90 °C, propanal content was increased in samples with 30% oil load spray-dried at 210/90 °C. The differences in stability could only partly be explained by the varying amount of extractable oil. It is concluded that the surface oil protects other fractions of the extractable oil and that the extractable oil cannot be used to predict shelf-life of microencapsulated oils.     

Effects of the drying method on the oxidative stability of the free and encapsulated fractions of microencapsulated sunflower oil

The influence of the drying method, freeze-drying and spray-drying, on the oxidative stability of microencapsulated sunflower oil depended on the type of encapsulation matrix. For a dairy-type matrix, formed by sodium caseinate and lactose, greater losses of tocopherols were detected during spray-drying, but both the free and encapsulated oil fractions were more stable against lipid oxidation than their freeze-dried counterparts. Results suggested that the free oil was also constituted by droplets that preserved their interfacial membrane and were protected by the matrix. Therefore, the free oil was not necessarily the non-encapsulated fraction. For a matrix constituted by gelatine, maltodextrin and sucrose, the emulsion showed low stability and a great destabilisation during spray-drying. No significant effect of the drying method on the oxidative stability of the encapsulated fraction was found with this matrix, but the free oil of the spray-dried sample oxidised faster, probably due to the emulsion destabilisation observed, which gave rise to a great amount of oil on the particle surface as a consequence of large droplets poorly stabilised.     

Microencapsulation properties of two different types of n-octenylsuccinate-derivatised starch

Aim of the present study was to evaluate the suitability of two different types of n-octenylsuccinate-derivatised starch, which significantly differed in viscosity, for microencapsulation of a fish oil rich in long-chain polyunsaturated fatty acids. Stable feed emulsions for microencapsulation could be prepared with both types of n--octenylsuccinate starch, however at a high oil load (50%), a low pH (pH 4.5) of the emulsion was crucial for emulsion stability. At 50% oil content, lower oil droplet size in reconstituted spray-dried emulsions and lower content of non-encapsulated oil was reached by low viscosity starch compared to medium viscosity starch. Conjugated dienes were significantly increased in samples with a high oil load and 40% starch indicating that to a certain degree lipid oxidation already occurred in these samples during the drying process. Finally, moderate spray-drying conditions must be considered as advantageous, since ballooning of the particles and lipid oxidation during spray drying were limited compared to drying at high spray-drying temperatures.     

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.     

响应面试验优化盐焗鸡卤汁分离鸡油微胶囊化工艺

以辛烯基琥珀酸淀粉钠和麦芽糊精为复合壁材对精炼过后的鸡油进行喷雾制作微胶囊鸡油。通过响应面分析法获得最佳微胶囊制作工艺条件为进风温度190 ℃、均质压力39 MPa、进样速率15 mL/min,最终微胶囊鸡油产品包埋率为95.9%。微胶囊鸡油呈规则球状,表明较光滑,减少了与外界接触的机会,减慢了氧化速率。产品经（60±1）℃加速氧化5 d后,过氧化值仅为对照样品的1/3,抗氧化效果明显。     

Physicochemical characterization and oxidative stability of fish oil encapsulated in an amorphous matrix containing trehalose

Fish oil with 33% omega-3 fatty acids was microencapsulated by spray-drying in a matrix of n-octenylsuccinate-derivatized starch and either glucose syrup or trehalose. Samples showed no difference in physicochemical properties as determined by measurement of particle size, oil droplet size, true density and BET surface. Upon storage at low relative humidity, lipid oxidation was decreased in trehalose containing samples indicating that in the amorphous state trehalose is a more suitable wall material for microencapsulation than glucose syrup. The retarded oxidation of trehalose containing samples may be attributed to the unique binding properties of trehalose to dienes. At 54% relative humidity, a rapid oxidation of the microencapsulated oil was observed upon crystallization of trehalose, which limits the range of applications to products to be stored at low humidity.     

New insights into the microencapsulation properties of sodium caseinate and hydrolyzed casein

The aim of the present study was to describe the fundamental physical characteristics of spray-dried carrier matrices based on sodium caseinate and casein hydrolyzate and microcapsules as well as their impact on the stability of a microencapsulated functional ingredient. Spray-dried carrier matrix was characterized by different physical methods (helium pycnometry, nitrogen displacement for surface area analysis, X-ray photoelectron spectroscopy, positron annihilation lifetime spectroscopy). Surface viscoelasticity of protein-stabilized oil–water interfaces was analyzed using dynamic pendant drop tensiometry. Fish oil was microencapsulated and microencapsulation efficiency as well as oxidative stability over time was monitored.     

Oxidatively Derived Volatile Compounds in Microencapsulated Fish Oil Monitored by Solid-phase Microextraction (SPME)

The stability of microencapsulated fish oil was studied during storage at 4 °C for up to 20 wk. Different coating mixtures consisting of gelatin or caseinate in blends with carbohydrates (sucrose, lactose, maltodextrin) were investigated. Oxidative stability of the microencapsulated fish oil was monitored by analysis of volatile compounds using gas chromatography olfactometry (GC‐O) or GC flame ionization (GC‐FID) (SPME‐HS‐GC/O or GC/ FID and HS‐GC/MS), Oxipres test, thiobarbituric acid‐reactive substances (TBARS), and sensory analysis. Coating mixture of caseinate and lactose showed slightly better stability than the sucrose and maltodextrin caseinate mixtures. Combination of fish gelatin and maltodextrin did not show as good oxidative stability as the coating blend of caseinate, lactose, and lecithin. Hexanal, 2‐nonenal and 2,4‐decadienals were selected as quality indicators to monitor the lipid oxidation during storage of the samples. SPME‐GC‐O analysis of these indicators showed that they were representative for the oxidation occurring in the microencapsulated fish oil. SPME‐GC‐FID analysis was sensitive enough to detect oxidative changes during storage. Oxidative stability test, TBARS results, and sensory analysis were in agreement with the SPME, indicating that SPME (polydimethylsiloxane/divinylbenzene [PDMS/ DVB] fiber) can be a useful tool for rapid analysis of lipid oxidation in microencapsulated fish oil.     

Impact of chitosan and oregano extract on the physicochemical properties of microencapsulated fish oil stored at different temperature

Fish oil is an excellent source of omega-3 fatty acids and is easily susceptible to oxidation. Microencapsulation is a commonly employed technique to protect fish oil against oxidation. In the present study, the potential of chitosan in combination with bovine gelatin and maltodextrin as wall material for microencapsulation of fish oil by spray drying was evaluated. To improve the oxidative stability of the fish oil microencapsulates, oregano (Origanum vulgare L) extract was added at 0.50 g/100 g of emulsion. The spray-dried powder showed a moisture content of 2.8 – 3.2 g/100 g of spray-dried powder. The powder contained spherical microparticles with different sizes as indicated by scanning electron microscope images. Encapsulation efficiency of microencapsulates ranged between 68.94% and 81.88%. Differential scanning calorimetry and Fourier-transformed infrared spectroscopy analysis of microencapsulates revealed the possible structural stabilization of core and wall material. The oxidative stability of fish oil microencapsulates were monitored under three different temperature (60°C, 28 ± 2°C, and 4°C). Incorporation of oregano extract minimized the generation of secondary and tertiary oxidation products as indicated by lower peroxide value and thiobarbituric acid reactive substance values compared to control. Overall, the results suggested that combination of chitosan along with bovine gelatin and maltodextrin as wall material improved the surface morphology of the microparticle and encapsulation efficiency, whereas incorporation of oregano extract in fish oil before spray drying enhanced the oxidative stability during storage.     

Encapsulation and Oxidative Stability of PUFA-Rich Oil Microencapsulated by Spray Drying Using Pea Protein and Pectin

This study aimed at evaluating the potential of pectin combination with pea protein isolate (PPI) in the microencapsulation of polyunsaturated fatty acids (PUFA)-rich oil by spray drying, in order to maximize encapsulation efficiency and minimize lipid oxidation. The feed emulsions used for particle production consisted of PUFA-rich oil droplets coated by either PPI (primary emulsion) or PPI–pectin (secondary emulsion). Dry emulsions characteristics and oxidative stability of microencapsulated oil as a function of relative humidity (RH; from 11 % to 75 %) were determined. Scanning electron microscopy (SEM) images revealed considerable structural changes. Oil droplets retained their shape upon drying and reconstitution. However, a shift in oil droplet size upon reconstitution indicated that oil droplet coalescence occurred within the process. Oxidation of microencapsulated oil in secondary emulsion was delayed from that of primary emulsion but followed the same pattern with regards to humidity. A high rate of oxidation was found for intermediate RH conditions (33 % and 57 % RH). The lowest rate of oxidation as followed by hydroperoxide and thiobarbituric acid reactive substances values was found at 75 % RH, a condition that is likely to diverge significantly from the monolayer moisture value. The oxidative stability of encapsulated oil was influenced by both physical state of the emulsions and the different constituents at the oil-in-water interface with PPI–pectin secondary emulsion giving the best protection of the oil.     

Microencapsulation of flaxseed oil in flaxseed protein and flaxseed gum complex coacervates

Flaxseed oil, a rich source of omega-3 fatty acids, was microencapsulated in a novel matrix formed by complex coacervation between flaxseed protein isolate (FPI) and flaxseed gum (FG). This matrix was crosslinking with glutaraldehyde. Liquid microcapsules with three core (oil)-to-wall ratios (1:2, 1:3 and 1:4) were prepared and spray-dried or freeze-dried to produce powders. The microencapsulation efficiency, surface oil, morphology and oxidative stability of these microcapsules were determined. The spray-dried solid microcapsules had higher oil microencapsulation efficiency, lower surface oil content, smoother surface morphology and higher oxidation stability than the freeze-dried microcapsules. The highest microencapsulation efficiency obtained in spray-dried microcapsules was 87% with a surface oil of 2.78% at core-to-wall ratio 1:4 and oil load 20%. The oxidation stability obtained from spray-dried microcapsules at core-to-wall ratio of 1:4 was nearly double that of the unencapsulated flaxseed oil.     

Critical evaluation of non-thermal plasma as an innovative accelerated lipid oxidation technique in fish oil

Food products enriched with healthier unsaturated fatty acids are more sensitive to lipid oxidation, leading to an overall quality deterioration and the development of unwanted aroma properties. To evaluate the oxidative stability a wide range of techniques has been described in literature, of which most are thermally based. These unrealistic test conditions result in the induction of deviating oxidation chemistry compared to that observed during ambient storage. Non-thermal plasma technology is capable to generate a wide range of highly reactive oxidative species (e.g. atomic oxygen, hydroxyl radicals, singlet oxygen) while maintaining ambient temperatures. For the first time, a DBD-plasma jet (Ar/0.6% O₂) is used on fish oil samples as a faster and more realistic accelerated lipid oxidation method. This paper critically evaluates both a thermal as a non-thermal plasma based accelerated oxidation protocol using naturally aged fish oil as reference. Experiments were done using both virgin, as alpha-tocopherol-enriched fish oil samples. Secondary lipid oxidation volatiles were measured using HS-SPME–GC–MS. Both accelerated oxidation techniques induced the formation of typical lipid oxidation markers (e.g. 2-propenal, (E)-2-pentenal, heptanal), however in both cases significant differences were observed compared to the naturally aged fish oil. On the other side, non-thermal plasma correctly predicted an antioxidative effect when 1000 μg/g alpha-tocopherol was added to the fish oil, while thermally based tests resulted in the induction of prooxidative chemistry. Despite the differences with naturally aged fish oil, several non-thermal plasma characteristics (reactor configuration, gas feed mixture, power source, …) can be fine-tuned to evolve towards a technology that is capable to accelerate lipid oxidation in a highly realistic manner.     

Influence of anionic dietary fibers (xanthan gum and pectin) on oxidative stability and lipid digestibility of wheat protein-stabilized fish oil-in-water emulsion

The influence of two anionic dietary fibers (xanthan gum and pectin) on the oxidative stability and lipid digestibility of fish oil emulsions stabilized by wheat protein (gliadin) was investigated. Lipid oxidation was determined by measuring lipid hydroperoxides and TBARS of the emulsions during storage, while protein oxidation was measured using fluorescence spectroscopy. Lipid and protein oxidation was faster at pH 3.5 than at pH 7, which may have been due to increased iron solubility under acidic conditions. Xanthan gum inhibited lipid and protein oxidation, which was attributed to its ability to bind iron ions. Conversely, pectin promoted oxidation, which was attributed to the presence of endogenous transition metals in the polysaccharide ingredient. In vitro digestion was carried out to evaluate the digestibility of oil droplets in emulsions with or without polysaccharides. Both xanthan gum and pectin significantly increased the rate of lipid digestion, which was attributed to their ability to inhibit droplet aggregation under gastrointestinal conditions. These results have important implications for designing emulsion-based functional foods with improved oxidative stability and lipid digestibility.     

A novel process for microencapsulation of fish oil with barley protein

This research represents the first scientific publication reporting barley protein as a wall material to encapsulate fish oil. Solid microcapsules were able to form in aqueous solution by pre-emulsifying barley proteins with a homogenizer followed a microfluidizer system. No organic solvent or cross-linking reagents were used in the preparation process. The wet status microcapsules were converted into free-flowing powder (dry status microcapsules) by a spray-drying process. The optimum microcapsule preparation conditions were 15% protein, oil/protein ratio = 1.0, and an inlet temperature of 150 °C. These microcapsules exhibited high encapsulation efficiency (EE: 92.9–100.2%), loading efficiency (LE: 46.5–50.1%) and low moisture content (0.75–0.90%). The oxidative stability of microencapsulated fish oil was tested at both dry status and in aqueous solutions (pH 7.0 and pH 2.0) in an accelerated storage test (40 °C, 8 weeks). These barley protein microcapsules possessed a strong ability to protect fish oil against oxidation, making them ideally suited for use in liquid/semi-liquid food systems. Food formulation tests confirmed their successful application in milk and yogurt for their respective shelf lives.     

均质压力及喷雾干燥温度对鱼油微胶囊化的影响

采用辛烯基琥珀酸酯淀粉Hi-Cap100和葡萄糖浆作为鱼油微胶囊的壁材。研究了不同均质压力下乳化液黏度、粒径和粒径分布规律,考察了不同均质压力下乳化液特性与鱼油微胶囊包埋率、表面油含量之间的相关性,探讨了喷雾干燥温度对包埋率和鱼油过氧化值(POV)的影响。研究结果表明,随着均质压力的增加,乳化液黏度和平均粒径逐渐减小,而粒径分布离散度总体呈下降趋势,在40MPa时最小,说明此时粒径分布均一性最佳;喷雾干燥温度增加时,鱼油包埋率先增后减,POV值先减后增,在进/出口温度为140℃/70℃时有最高的包埋率和最低的POV值。通过分析确定最佳工艺参数如下,均质压力为40MPa,喷雾干燥进口温度为140℃,出口温度为70℃。在上述最适工艺条件下,鱼油微胶囊平均粒径为5.97μm,表面油含量为2.03%,微胶囊化包埋率为95.6%,在扫描电镜下观察微胶囊表面和内部结构良好,具有良好的包埋效果。     

不同风干工艺处理的武昌鱼鱼肉品质和风味的变化

以腌制武昌鱼为原料进行干制,通过测定热泵干燥、热风干燥、冷风干燥、联合干燥四种风干工艺处理下的武昌鱼鱼肉脂质氧化理化指标,感官,色泽,质构特性,电子鼻,挥发性风味成分变化,分析不同干燥工艺处理对武昌鱼品质特性和风味变化的影响。热泵干燥的武昌鱼脂质氧化程度更显著,初级产物氢过氧化物含量最高为4mmol/kg,脂质氧化二级产物丙二醛含量最高为0.68 mg/kg,感官评分结果最好（8.6分）、质构表现最好;冷风干燥处理的武昌鱼色泽表现最差,热风、热泵、联合干燥处理的武昌鱼差异较小;热风干燥处理的武昌鱼硬度最大53.96 N、热泵干燥处理的武昌鱼弹性最大;电子鼻检测表明四种干燥工艺处理武昌鱼风味呈现显著性差异（P<0.05）;挥发性风味物质检测发现联合干燥处理武昌鱼挥发性风味物质含量最多21种,热泵处理挥发性风味物质含量最低仅有6种。综上所述联合干燥处理的武昌鱼鱼肉,脂质氧化程度硬度低、弹性好、挥发性风味物质含量多种类丰富。     

鱼油微粉的制备及其稳定性分析

为优化鱼油微粉的制备工艺以及初探其稳定性,本文以鱼粉加工副产物富集所得鱼油为原料,筛选复合壁材,研究喷雾干燥法制备鱼油微粉的工艺条件,考察芯壁比、固形物浓度、乳化温度、进风温度、喷雾压力、进料流量等因素对鱼油微胶囊效果的影响,并测定鱼油微粉的微观结构、溶解性及稳定性。结果表明,壁材选择阿拉伯胶/β-环糊精/玉米糖浆（质量比2:1:6）效果较好,微粉制备的最适工艺参数为:芯壁比32%、固形物浓度25%、乳化温度52 ℃、进风温度206 ℃、喷雾压力35 MPa、进料流量300 mL/h,此条件下制得的鱼油微粉包埋率达92.66%。微粉颗粒表面光滑,无破裂或孔洞,且水溶性好。鱼油微粉的贮藏稳定性显著高于未微胶囊化的鱼油（P<0.05）,且添加抗氧化剂的微胶囊鱼油具有更好的抗氧化能力。     

Sensory odour profiling and lipid oxidation status of fish oil and microencapsulated fish oil

The aim of the present study was to evaluate the suitability of defined odour attributes for the sensory evaluation of bulk fish oil and reconstituted microencapsulated fish oil as well as the active modification of the sensory profile during storage. Common attributes previously described for bulk fish oil (fishy, metallic, pungent, green notes) proved to be suitable for the sensory evaluation of reconstituted microencapsulated fish oil. Additional attributes were identified in dependence on the bulk fish oil processing (sweet/biscuit-like) and of constituents of the microcapsule carrier matrix (seasoning-like). Reconstituted sodium caseinate-based microcapsules exhibited a lower fishy odour during storage than did n-octenylsuccinate-derivatised starch-based microcapsules, probably due to the oxidative status. Flavour binding of caseinate may be of minor importance in reconstituted microencapsulated fish oil. Improvement of the sensory profile was achieved by the addition of an odour-masking compound (β-cyclodextrin) or flavouring (vanillin and apple flavour).     

Effect of Relative Humidity on the Oxidative Stability of Microencapsulated Sea Buckthorn Seed Oil

ABSTRACT: The effect of relative humidity (RH) (20 °C: RH 11%, 54%) on oxidative stability microencapsulated sea buckthorn seed oil was studied using bulk oil as a reference. Microcapsules were prepared by spray-drying using maltodextrin-gum arabic (MD/GA) and corn starch sodium octenyl succinate derivate (HiCap) as the wall materials. The influence of the physical state of the wall material was also evaluated. Under dry conditions, the microencapsulated oils were most stable, but the oxidation of the bulk oil was accelerated. At 20 °C and at RH 11%, the peroxide value of the bulk oil exceeded 20 meq/kg within 1 wk. Microencapsulation prolonged the shelf-life of the oil from 1 wk to 2 mo at 20 °C, when the encapsulating matrix was in glassy state. In conditions in which the HiCap matrix was in a rubbery state (RH 54%, 20 °C), the oxidation proceeded very quickly, reaching a peroxide value of 20 meq/kg just after 1 wk. Caking and collapse of the microcapsule powder were observed in the rubbery state. At accelerated conditions (50 °C: RH 11%, 30%, 45%), the oxidation was noticeably fast, not only in the bulk oil but also in the MD/GA matrix, even in the glassy state. The behavior in the HiCap matrix was more complex as the amount of peroxides started to decrease in time. This was assigned to the structural collapse in HiCap microcapsules. The behavior of the microencapsulated oils under accelerated conditions did not correlate with their behavior at 20 °C.     

The Influence of Drying Process Conditions on the Physical Properties,Bioactive Compounds and Stability of Encapsulated Pumpkin Seed Oil

In this study, the influence of encapsulation process conditions on the physical properties and chemical composition of encapsulated pumpkin seed oil was investigated. Four variants of encapsulated oil were prepared: spray-dried non-homogenized emulsions at the inlet temperatures of 180 and 130 °C, spray-dried homogenized emulsion at the inlet temperature of 130 °C, and freeze-dried homogenized emulsion. The emulsion was prepared by mixing 10.6% oil with 19.8% wall materials (15.9% maltodextrin + 0.5% guar gum + 3.9% whey protein concentrate) and 69.6% distilled water. The quality of encapsulated pumpkin seed oil was evaluated by encapsulation efficiency, surface oil, total oil and moisture contents, flowing properties, color, and size. Additionally, fatty acid composition, pigment characteristics, and the content of bioactive compounds (tocopherols, squalene, and sterols) were determined. Changes of these components after the encapsulation process in comparison to the control pumpkin seed oil were considered as stability parameters. The highest encapsulation efficiency was obtained by spray-drying at the inlet temperature of 130 °C. Generally, the spray-drying process had a positive effect upon the physical parameters of encapsulated pumpkin seed oil but results were dependent on process conditions. The higher inlet temperature generated more surface oil, but capsules obtained at the lower temperature were greater in size and more deformed. Although freeze-drying proceeded at a very low temperature, the powder obtained with this technique was characterized by the highest bioactive compound losses (with the exception of sterols) and the lowest stability. The homogenization process applied before spray-drying affected greater polyunsaturated fatty acid, squalene, and pigment degradation. In conclusion, results of the study showed that the spray-drying non-homogenized emulsion was a more recommendable technique for the encapsulation of pumpkin seed oil because of smaller changes of native compounds and better oxidative stability.