Optimizing microencapsulation of peanut sprout extract by response surface methodology

This study was carried out to optimize conditions for peanut sprout extract microencapsulation by response surface methodology (RSM). The coating materials of microencapsulation were medium-chain triacylglycerol (MCT) for primary emulsion, and whey protein concentrates (WPC), maltodextrin (MD) and gum Arabic (AG) for secondary emulsion. The yield of microencapsulation of peanut sprout extract was investigated with respect to four variables (ratio of core and coating materials, concentration of primary emulsifier, ratio of W/O emulsion and secondary coating materials and concentration of secondary emulsifier) in RSM. The optimal conditions for microencapsulation of peanut sprout extract were 1:2 as the ratio of core material to coating material, 1.25% (w/v) of primary emulsifier concentration, 1:1.23 as W/O emulsion to secondary coating material, 1.21% (w/v) as secondary emulsifier concentration and 30% (w/w) as WPC concentration for spray drying. In conclusion, the microencapsulation of peanut sprout extract under the optimized conditions by RSM ensures the smaller size (3–7 μm) of microcapsules with the highest yield reaching to 98.74%.     

不同壁材对大豆生物解离乳状液微胶囊品质的影响

为拓宽大豆生物解离乳状液的综合应用,有效解决破乳困难问题,本文采用喷雾干燥法制备大豆生物解离乳状液微胶囊,以乳液的乳化活性、乳化稳定性、粒径分布、流变学性质和喷雾干燥制得的微胶囊包埋率、热稳定性、表面微观结构为指标,研究5种复合壁材对大豆生物解离乳状液微胶囊品质的影响。结果表明,喷雾干燥前,CMC-MD为壁材的混合乳液的黏度最高,为39.18 mPa·s,且乳化性较好,粒径分布向较小粒径方向移动至0.6~2.0 μm。CMC-MD复合壁材制备的微胶囊包埋率最高,达到90.3%,热稳定性最好,结构变化起始温度最高,为98.3℃。扫描电镜图(SEM)显示不同壁材包埋的微胶囊呈现规则的球形或椭球形颗粒,颗粒直径有一定的差异,以CMC-MD为壁材的微胶囊大小均一,结构致密,具有良好的包埋结构,说明CMC-MD能够作为大豆生物解离乳状液微胶囊的壁材,制备出的微胶囊具有良好的包埋率、热稳定性及表面微观结构,对于生物解离乳状液加工应用领域的拓展和产业化的发展具有重大意义。     

喷雾干燥法制备可控释微胶囊及其释放性能研究

分别以VB1、ACE抑制肽和牛血清白蛋白为芯材,以聚丙烯酸树脂Ⅱ和乙基纤维素水分散体为壁材,按芯材/壁材比为1:10,喷雾干燥法制备微胶囊,并研究芯材在模拟胃肠液中的释放性能。分析结果表明,聚丙烯酸树脂Ⅱ微胶囊为表面光滑的圆球,乙基纤维素水分散体微胶囊表面有凹陷,芯材包埋率均大于98%。聚丙烯酸树脂Ⅱ微胶囊在模拟胃液中120 min芯材累计释放率小于10%,在模拟肠液中60 min则完全释放;乙基纤维素水分散体微胶囊在模拟胃肠液中芯材释放速率基本一致,120 min累计释放率达70%以上。以聚丙烯酸树脂Ⅱ为壁材的微胶囊可以实现在胃肠液中可控制释放芯材。     

Novel microwave–freeze drying of onion slices

The present study aimed to introduce the capability of a novel dehydration technique. To do so, slices with various thicknesses (3.5 and 7 mm) of white onions were dried using commercial freeze drier (abs. pressure 0.005 mbar, temp. 45 °C), our own designed microwave-vacuum drier (abs. pressure down to 300 mbar) under various microwave powers (120–1200 W) and microwave-vacuum–freeze drier (onion slices kept at −20 °C for 2 h). Then, their dehydration rates and some quality parameters, such as rehydration ratio, colour ( L*, a* and b* ) and micro-structure were investigated. Our findings showed that microwave-vacuum–freeze drier is practically a rapid, simple, efficient, economic and novel dehydration technique which can be used for dehydration of mainly foodstuffs. The quality properties of slices produced by this novel method were also completely comparable and competitive with commercial freeze drier with over 96% saving on processing time and enormous amount on energy and capital investments.     

Optimization of Incorporated Prebiotics as Coating Materials for Probiotic Microencapsulation

ABSTRACT: The purpose of this research was to improve probiotic microencapsulation using prebiotics and modern optimization techniques to determine optimal processing conditions, performance, and survival rates. Prebiotics (fructooligosaccharides or isomaltooligosaccharides), growth promoter (peptide), and sodium algi-nate were incorporated as coating materials to microencapsulate 4 probiotics ( Lactobacillus acidophilus, Lacto-bacillus casei, Bifidobacterium bifidum , and Bifidobacterium longum ). The proportion of the prebiotics, peptide, and sodium alginate was optimized using response surface methodology (RSM) to 1st construct a surface model, with sequential quadratic programming (SQP) subsequently adopted to optimize the model and evaluate the survival of microencapsulated probiotics under simulated gastric fluid test. Optimization results indicated that 1% sodium alginate mixed with 1% peptide and 3% fructooligosaccharides as coating materials would produce the highest survival in terms of probiotic count. The verification experiment yielded a result close to the predicted values, with no significant difference ( P > 0.05). The storage results also demonstrated that addition of prebiotics in the walls of probiotic microcapsules provided improved protection for the active organisms. These probiotic counts remained at 10⁶ to 10⁷ colony-forming units (CFU)/g for microcapsules stored for 1 mo and then treated in simulated gastric fluid test and bile salt test.     

Microencapsulation of Essential Oil for Insect Repellent in Food Packaging System

Microcapsules containing thyme oil were prepared by in situ polymerization, using melamine–formaldehyde prepolymer as a wall material and 3 different emulsifiers (pluronic F‐127, tween 80, and sodium lauryl sulfate [SLS]). The general characteristics and release behavior of microcapsules, and their repellent effect against insects were investigated. The morphology of microcapsules using SLS was spherical shape with smooth surface. Microcapsules began to degrade at 150 °C. The particle size ranged from 1 to 10 μm and the loading efficiency of thyme oil was clearly affected by the emulsifier type. The highest loading efficiency appeared in microcapsules using SLS, which have good thermal resistance and smooth surface. The release rate of thyme oil from microcapsules was not only dependent on the storage temperature but also emulsifier type and microcapsules showed the sustained release properties for a long time. Diets, which were mixed with encapsulated thyme oil, expressed high insect repellent efficacy over 90% for 4 wk. Practical Application : Essential oil has various pest‐control characteristics, including repellent, ovicidal, and antifeedant efficacy. This work showed the sustained release properties and long‐lasting repellency of encapsulated essential oil. The results suggest that the great potential of essential oil microcapsules can be applied in coating or printing of food packaging materials for the insects repelling effects.     

Effect of Homogenization Techniques on Reducing the Size of Microcapsules and the Survival of Probiotic Bacteria Therein

ABSTRACT:  This study investigated 2 different homogenization techniques for reducing the size of calcium alginate beads during the microencapsulation process of 8 probiotic bacteria strains, namely,  Lactobacillus rhamnosus ,  L. salivarius ,  L. plantarum ,  L. acidophilus ,  L. paracasei, Bifidobacterium longum ,  B. lactis  type Bi-04, and  B. lactis  type Bi-07. Two different homogenization techniques were used, namely, ultra-turrax benchtop homogenizer and Microfluidics™ microfluidizer. Various settings on the homogenization equipment were studied such as the number of passes, speed (rpm), duration (min), and pressure (psi). The traditional mixing method using a magnetic stirrer was used as a control. The size of microcapsules resulting from the homogenization technique, and the various settings were measured using a light microscope and a stage micrometer. The smallest capsules measuring (31.2 μm) were created with the microfluidizer using 26 passes at 1200 psi for 40 min. The greatest loss in viability of 3.21 log CFU/mL was observed when using the ultra-turrax benchtop homogenizer with a speed of 1300 rpm for 5 min. Overall, both homogenization techniques reduced capsule sizes; however, homogenization settings at high rpm also greatly reduced the viability of probiotic organisms.     

干酪乳杆菌/乳糖醇双层合生元微胶囊制备及其在橙汁中的应用

目的:利用酶促法制备干酪乳杆菌/乳糖醇合生元微胶囊,研究乳糖醇浓度对微胶囊特性的影响,并对制备的微胶囊开展应用研究。方法:以黏玉米来源谷氨酰胺转氨酶(TGZ)为催化剂,以酪蛋白和海藻酸钠为壁材,通过内源乳化法对合生元进行双层包埋。利用粒径和干酪乳杆菌在模拟胃肠液中的存活率为指标,确定乳糖醇的添加量,并对其进行形态学观察。最后将制备的微胶囊添加到橙汁饮料中,评价干酪乳杆菌在低温贮藏时的存活情况。结果:TGZ可以交联酪蛋白对干酪乳杆菌/乳糖醇合生元进行包埋。当乳糖醇添加量为1.0 g/100 mL时,双层包埋的微胶囊粒径最小,包埋率最大为61.73%。在模拟胃肠液实验中,添加1.0 g/100 mL的乳糖醇可以提高干酪乳杆菌的存活率。扫描电镜结果表明,干酪乳杆菌完全包裹在壁材中,表明微胶囊的抗穿透物理屏障对益生菌的保护作用。贮存试验发现,添加乳糖醇后橙汁中的活菌数比未添加乳糖醇的高0.56个对数值。结论:双层微胶囊对乳酸菌的存活有很好的保护作用,且乳糖醇的存在也可以提高益生菌的存活率,因此益生菌/乳糖醇合生元微胶囊在食品,尤其是功能性食品方面具有广阔的应用前景。     

Characterizing the pH-Dependent Release Kinetics of Food-Grade Spray Drying Encapsulated Iron Microcapsules for Food Fortification

Iron deficiency is the primary cause of many widespread nutritional diseases including anemia, pregnancy complications, and infant mortality. Release kinetics of iron premixes to be mixed with food items like salt, rice, and tea is a key research objective of many globally active iron fortification efforts. Iron release kinetics of microcapsules of two reverse-enteric coating materials (chitosan and Eudragit EPO) encapsulating various amounts of ferrous sulfate (10–40% of total other solids) were done at three pH values (1, 4, 7) for 2 hours. Chitosan and Eudragit microcapsules contained 2.8–5.3% (w/w) and 1.7–9.6% (w/w) iron, respectively, depicting higher iron loading capacity of Eudragit microcapsules. More than 90% iron was released from most samples within 30 min under stomach conditions (pH 1) and less than 15% iron was released in 2 h under ambient conditions (pH 7), showing suitability of both chitosan and Eudragit EPO as reverse-enteric coatings for iron encapsulation. In terms of reverse-enteric behavior (RE), Eudragit EPO (RE = 2.4) was found to be slightly better than chitosan, suggesting the use of fillers in future research. Higuchi model and Hixson-Crowell model were found to best fit the data, suggesting a transport phenomenon governed by both (a) the diffusion process through the coating material and (b) the dissolution phenomenon resulting in decrease in size of the capsules. Results from this study shall provide guidance for technology development aspects of various food fortification initiatives and an understanding of the iron release from these fortificants during the food preparation and digestion stages.     

Native and modified porcine plasma protein as wall materials for microencapsulation of natural essential oils

Porcine plasma protein (PPP) is of interest as a wall material to encapsulate lemongrass oil, turmeric oil and eucalyptus oil using emulsion technique and freeze drying. The properties of microcapsules were used to evaluate two types of wall material (native porcine plasma protein; NPPP and modified porcine plasma protein; MPPP) at two different ratios of wall material (W) and core material (C) (W:C; 4:1 and 3:1). All NPPP and MPPP emulsions showed Bingham plastic fluid flow behaviours. Moreover, MPPP microcapsules showed lower free oil content on their surface (0.10–0.50%) with higher encapsulation efficiency (91–98%). Fourier-transform infrared spectroscopy showed the outstanding chemical structure of microcapsules. Furthermore, scanning electron microscopy indicated holes on the surface of microcapsules encapsulated with essential oils. Both PPPs can be used as encapsulation material for natural extract and food additives to improve the food texture and as a biopolymer film to maintain the quality of food products.     

猕猴桃籽油微胶囊在Caco-2单细胞层的吸收特性

以玉米肽为壁材,猕猴桃籽油为芯材,吐温-20为乳化剂,采用喷雾干燥法制备猕猴桃籽油微胶囊。MTT试验结果表明,当微胶囊浓度≤400μg/mL时,其对Caco-2细胞生长无明显抑制作用,且质量浓度为100~400μg/mL的微胶囊对细胞的生长有促进作用。对微胶囊在Caco-2单细胞层的吸收特性进行研究,结果表明,微胶囊在高、中、低3个浓度时,微胶囊的生物利用率均高于25%。当质量浓度为100μg/mL时,微胶囊的生物利用率达到最高,为41.70%±1.65%。微胶囊溶液从AP侧到BL侧的表观渗透系数Papp在1×10^-7~1×10^-6cm·s^-1之间,吸收水平较好。     

THIN-LAYER INFRARED RADIATION DRYING OF RED PEPPER SLICES

Drying characteristics and changing of quality parameters of red pepper were determined experimentally as a function of infrared power ( IP ) and air velocity during infrared drying. Drying experiments of red pepper slices were carried out at three levels of IP (300, 400 and 500 W) and at three air velocities (1.0, 1.5 and 2.0 m/s). The drying time at air velocity from 1.0 to 2.0 m/s ranged between 314 and 455 min, 213 and 297 min and 196 and 230 min at IP of 300, 400 and 500 W, respectively. Drying rate increased with increasing IP and decreasing air velocity. All drying experiments had a falling rate of drying period. The specific energy consumption was varied between 4.62 and 7.59 kW·h/kg for all the drying conditions. Thickness change/shrinkage was found to be in the range of 0.162 and 0.263. The color parameters and the rehydration ratio were significantly influenced by IP and air velocity.

PRACTICAL APPLICATIONS

Drying is an important operation in red pepper processing. In open-air condition, the drying time of red pepper is 8–10 days. Several researchers state that drying in open-air conditions also has some disadvantages such as lack of ability to control the drying operation properly, long drying time, weather uncertainties, high labor costs, large area requirement, insect infestation and contamination with dust and other foreign materials. The results from this study can be used as reference for drying of red pepper in similar applications. The drying method proposed in this study decreased the time required for drying of red pepper, reduced the space needed for equipment and protected the product quality. Therefore, the drying technique proposed in this study can be a good alternative to other drying techniques available. Also, the proposed drying method can be used as a reference to drying applications of various vegetables and fruits.     

Effect of edible coatings on the quality of frozen fish fillets

The objective of this study was to determine the changes in the quality of coated trout fillets after coating with edible materials. Fillets were coated and stored at −18 °C for a period lasting up to 7 months. Coating materials were applied in three different stages (first, second, and last coatings). The coated fillets were fried and analyzed for oil absorption and moisture content throughout the storage period. Sensorial attributes and the physical-biochemical changes were also measured before the frying process in each month. It was observed that it is more advantageous to use gluten as the first coating, xanthan gum as the second coating, and wheat (W) and corn (C) flours in the ratio of 1:1 or 2:1 as the last coating. In terms of the fillet quality, the following results were obtained in the analyses conducted before frying. The lowest pH found was 6.25 in zein-containing samples and 6.30 in guar-containing samples. The effects of the last coatings on pH were unimportant (P > 0.05). The lowest thiobarbituric acid levels found were 2.07 mg kg in the fillets coated with casein mixture, 2.44 mg kg in the fillets coated with xanthan gum, and 2.25 mg kg in the fillets coated with W:C flour mixture in the ratio of 2:1. The lowest total volatile basic nitrogen levels found were18.06 mg 100 g in the fillets coated with casein mixture, 18.62 mg 100 g in the fillets coated with xanthan gum, and 18.47 mg 100 g in the fillets coated with W:C flour mixture at 1:1 ratio. In the sensorial analysis, the coated samples were much more preferred than those not coated. As a result of the effects of all the materials, the coating layers on the meat surface provided more resistance against mass transfer during storage.     

辣椒红色素复凝聚微囊化工艺研究

目的以大豆分离蛋白(soybean protein isolate,SPI)和壳聚糖(chitosan,CH)为壁材,采用复凝聚法制备辣椒红色素(paprika red pigment,PRP)微胶囊。方法以微胶囊的包埋产率和包埋效率为指标,研究搅拌转速、复凝聚p H、温度、时间及SPI/CH比对微囊化效果的影响。结果 SPI/CH复凝聚法制备PRP微胶囊的最佳工艺为:将均匀的PRP乳状液冷却至室温,按SPI:CH=4:1(m:m)加入0.6%的CH溶液,此时固形物浓度为1.5%,用10%Na OH溶液调节混合液的p H至6.3,25℃、300 r/min条件下搅拌15 min得到微胶囊悬浮液,此时微胶囊的包埋产率为90.05%,效率为95.08%。所得微胶囊大小不均一,多以球形形式存在。结论 SPI/CH复凝聚体系可用于PRP的微囊化。     

An Improved Method of Microencapsulation of Probiotic Bacteria for Their Stability in Acidic and Bile Conditions during Storage

ABSTRACT: The purpose of this study was to develop a method for applying an extra coating of palm oil and poly‐L‐lysine (POPL) to alginate (ALG) microcapsules to enhance the survival of probiotic bacteria. Eight strains of probiotic bacteria including Lactobacillus rhamnosus, Bifidobacterium longum, L. salivarius, L. plantarum, L. acidophilus, L. paracasei, B. lactis type Bl‐O4, and B. lactis type Bi‐07 were encapsulated using alginate alone or alginate with POPL. Electron microscopy was used to measure the size of the microcapsules and to determine their surface texture. To assess if the addition of POPL improved the viability of probiotic bacteria in acidic conditions, both ALG and POPL microcapsules were inoculated into pH 2.0 MRS broths and their viability was assessed over a 2‐h incubation period. Two bile salts including oxgall bile salt and taurocholic acid were used to test the bile tolerance of probiotic bacteria entrapped in ALG and POPL microcapsules. To assess the porosity and the ability of the microcapsule to hold small molecules in an aqueous environment a water‐soluble fluorescent dye, 6‐carboxyflourescin (6 FAM), was encapsulated and its release was monitored using a UV spectrophotometer. The results indicated that coating the microcapsules with POPL increased the overall size of the capsules by an average of 3 μm ± 0.67. However, microcapsules with added POPL had a much smoother surface texture when examined under an electron microscope. The results also indicated that the addition of POPL to microcapsules improved the average viability of probiotic bacteria by > 1 log CFU/mL when compared to ALG microcapsules at 2 h of exposure to acidic conditions. However, similar plate counts were observed between ALG and POPL microcapsules when exposed to bile salts. This suggests that an extra coating of POPL could be readily broken down by bile salts that are commonly found in the lower gastrointestinal tract (GIT). Upon testing the porosity of the microcapsules, findings suggest that POPL microcapsules were less porous and hold 52.2% more fluorescent dye over a 6‐wk storage period.     

棉织物的原位聚合和紫外固化微胶囊芳香整理

采用原位聚合法制备了茉莉香精微胶囊,并通过紫外线固化的方式对棉织物进行芳香整理。红外光谱(FTIR)和光学显微镜(OM)结果显示,其平均粒径为2.6μm,具有良好的热稳定性。通过紫外光固化黏合剂可以实现微胶囊在棉织物上低温条件下固着。当不饱和聚氨酯预聚体为20%,光引发剂Runte-cure1265为2%时,涂层织物烘干后在1 000 W的高压紫外线光源下固化4 min,制得的芳香织物可以经受30次家庭洗涤,整理后的织物强力和硬挺度都有提高。     

正十六烷在芳香微胶囊中的应用研究

以薰衣草香精和正十六烷为复合芯材,聚甲基丙烯酸甲酯为壁材,采用乳液聚合法制备芳香微胶囊。应用扫描电子显微镜、激光粒度仪、紫外分光光度计及热重分析仪表征芳香微胶囊的表观形貌、粒径、包覆率及热稳定性。结果表明:添加正十六烷后,香精的包覆率显著增大;当W正十六烷∶W香精=6∶4时,芳香微胶囊包覆率达到74.5%,微胶囊表面光滑,球形度良好,平均粒径为300 nm,具有良好的芳香缓释效果,说明正十六烷不仅有效提高了香精的包覆率,而且增强了壁材对香精的保护作用。     

Microencapsulation of camellia oil to maintain thermal and oxidative stability with focus on protective mechanism

Camellia oil (CO) microcapsules were developed using chitosan–soybean protein isolate (CS-SPI) complexes as wall materials and transglutaminase (TGase) as the cross-linking agent. Results indicated that CO/SPI under the ratio of 1:2 exhibited the highest microencapsulation efficiency and yield, possessing the best encapsulation effect. Morphology observation showed that CO microcapsules were intact, compact and nearly spherical. The microencapsulated CO exhibited the improved thermal resistance and significantly lower peroxide values after 3 days storage, demonstrating that the produced microcapsule was a promising way to maintain the thermal and oxidative stability of camellia oil. It could be found evidence from FTIR, which indicated that covalent cross-linking and hydrogen bonding might be involved among wall materials, and physical interactions between the core and wall materials. Therefore, the produced CO microcapsules could be an effective way to protect camellia oil, which was helpful for improving the processing and storage qualities of camellia oil.     

Drying of carrot slices using infrared radiation

Carrot slices were dried from initial moisture content of 8.52 kg water kg⁻¹ dry matter to 0.11 kg water kg⁻¹ dry matter by infrared dryer. Experiments were conducted using three levels of infrared power (300, 400 and 500 W) and at air velocities (1.0, 1.5 and 2.0 m s⁻¹). The effects of process variables on the drying kinetics of carrot, drying time, specific energy consumption and quality parameters of dried carrot (shrinkage, rehydration ratio and colour) were investigated. The drying time at infrared power of 300, 400 and 500 W was 252 and 277 min, 205 and 236 min, and 145 and 155 min at air velocities of 1.0 and 2.0 m s⁻¹, respectively. The drying rate increased with increasing infrared power. The specific energy consumption values varied between 12.22 and 14.58 MJ kg⁻¹-evaporated water for all the drying conditions. Shrinkage, rehydration ratio and colour parameters were found to be affected by process variables.     

Physicochemical Properties and Storage Stability of Lutein Microcapsules Prepared with Maltodextrins and Sucrose by Spray Drying

The purpose of this study was to determine the physicochemical properties of lutein microcapsules. Nine types of lutein microcapsules were prepared in order to determine their encapsulation efficiency and yield. Results show that lutein microcapsules with maltodextrin M040 and sucrose at the weight ratio of 3:1 (designated as M040:1) had the highest encapsulation efficiency (90.1%) among the lutein microcapsules, as well as a higher encapsulation yield (90.4%). The onset glass transition temperatures (T_gi) and the surface dents of the lutein microcapsules decreased as the dextrose equivalent value of maltodextrin and the weight ratio of sucrose increased. Enthalpy relaxation experiments were conducted for the lutein microcapsules M040:1 at (T_gi – 5) , (T_gi – 10), and (T_gi – 15) °C, and the obtained data were fitted to the Kohlrausch–Williams–Watts model. Results show that the mean relaxation time (τ) (316 h) of M040:1 lutein microcapsules aged at (T_gi – 15) °C was greater than the τ (161 h) at (T_gi – 10) °C and τ (60.5 h) at (T_gi – 5) °C. Effects of temperature and oxygen transmission rates for package film on the storage stability of M040:1 lutein microcapsules were also investigated. Findings show that rates of lutein degradation and color change increased by an order of magnitude as storage temperature (4 to 97 °C) and oxygen transmission rate of the package film (0.018 to 62.8 cc/m² day) increased. These results suggest that lutein is highly unstable and susceptible to thermal and oxidative degradations. However, microencapsulation with appropriate wall materials of higher relaxation time and high oxygen barrier packaging can increase the storage life.