Food Engineering
Mohammad Khalilian-Movahhed; Mohebbat Mohebbi; Charlotte Sinding
Abstract
IntroductionEfforts have always been made to protect valuable compounds of medicine, food and aromatics materials that are highly sensitive to environmental conditions by the encapsulation method. encapsulation of flavors, in addition to its protection, allows the aromatic substance to be released in ...
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IntroductionEfforts have always been made to protect valuable compounds of medicine, food and aromatics materials that are highly sensitive to environmental conditions by the encapsulation method. encapsulation of flavors, in addition to its protection, allows the aromatic substance to be released in a long time, and the time and place of its release can be controlled. To design these protection systems requires detailed information on encapsulation and release methods, the nature of walls and aromatic materials (Gunning et al.,1999). For encapsulation of sensitive compounds such as lipophilic materials, it is necessary to produce an emulsion of the desired substance in wall materials such as proteins, polysaccharides or a mixture of them. The important factors in encapsulation are the molecular weight, chemical properties and polarity of the core materials, the properties of the materials of the walls, and finally, the methods used to produce microcapsules. (Jafari et al., 2008).The aim of this study was to produce and evaluate the properties of two and six layer multilayer microcapsules containing limonene using soy protein isolate and starch modified by spray drying. The release of encapsulated limonene was investigated under artificial oral conditions under different stress conditions. The results of this study can be used to predict the release rate of the encapsulated flavors and their release conditions.Materials and MethodsSolution preparation: The solution of SPI (0-3%) was prepared by methods of Huang et al. (2012). The OSA starch stock solution (0-2%) was prepared by methods of Nilsson and Bergens (2007).Emulsion’s preparation: the primary emulsion of the optimum SPI and secondary emulsion of optimum OSA starch concentration prepared by the method of Noshad et al (2015).Microcapsule production: To prepare the Microcapsules, a laboratory spray dryer was used. 180±5 ᵒC, inlet air temperature, 25 (ml/min) feed rate, and 90±10 ᵒC outlet air temperature were used. Six layer microcapsules was also prepared in the same conditions (Ansarifar et al., 2017)The micro structure, morphology and release of limonene were evaluated and finally by Zero order, First order, Higuchi, and Korsemeyer- peppas models were used to the fitting of experimental data.Limonene release: To investigate the release of the encapsulated limonene, the release of these microcapsules (two and six layer) at 37 ° C and pH = 6.8, as well as frequent chewing (0, 50 and 100 rpm) were examined. For the apply of shear stress, an oral simulator was designed and developed by the Department of Food Science and Technology of Ferdowsi University of Mashhad was used. Results and DiscusionThe results of particle size changes of the initial emulsion formed with different levels of soy protein isolate showed that the particle size decreased with increasing the concentration of this protein to 1.5% and then it was increased. The results of zeta potential showed that with increasing the concentration of soy protein isolate to 1.5%, the zeta potential of the samples increased and with more than 1.5%, it did not have much effect on the zeta potential of the samples, which indicates that concentrate of 1.5% soy protein isolate has a good ability to cover surface of limonene particles. Similarly, 1.2% of OSA starch was determined for the secondary layer.SEM images of the microcapsules showed that in the two-layer wall microcapsules have cavities, cracks and shrinkage. In the starting of drying, the rate of moisture lost is high and on the other hand, the wall is not strong enough to withstand the stresses caused by the exit of moisture from the walls, so the microcapsule has cavities. In six-layer microcapsules, a smooth, non-cracked surface was observed, which can be attributed to the wall strength due to the increase in the number of layers. Fourier transform infrared spectroscopic (FTIR) test showed that the outer surface of the microcapsules was covered by OSA starch in two and six layer microcapsules.The release profile of encapsulated limonene showed that the release rate in two layer samples was faster than six layer samples. Also, with increasing shear rate, the amount of release increased. The results of experimental models fitting showed that the first-order model had the best description for releasing limonene from two- and six-layer samples in different conditions. Calculation of diffusion coefficient showed that six-layer microcapsules have a lower diffusion coefficient than two-layer microcapsules, which leads to a decrease in the release rate of limonene.Conclusion The results of this study showed that the layer-by-layer method could be used to produce limonene microcapsules. Soy protein isolate and modified starch can cover limonene droplets well. SEM images showed that the structure of six-layer microcapsules is free of cracks and cavities and has a more uniform surface than two-layer microcapsules. To investigate the mechanism of limonene release from two- and six-layer microcapsules, different kinetic models were used to fit the experimental release data. The results showed that the release of these microcapsules occurred based on the diffusion mechanism and Fick's law, which is the main mechanism of mass transfer in the release process. Also, the results showed that the six-layer microcapsules had a lower diffusion coefficient than the two-layer microcapsules and the release rate was lower in the two-layer microcapsule; This is due to the repetitive coating of soy protein isolate and modified starch around the microcapsules and the increase in wall thickness.
Afshin Faridi Esfanjani; Seyed Mahdi Jafari; Elham Assadpour; Habibollah Mirzaee
Abstract
Introduction: Controlling and targeting release of bioactive compounds have a key role in improving their functional properties such as antioxidant and anti-disease activities. Encapsulation is one of the best methods for protection and controlling release of bioactive ingredients. Indeed, in this process, ...
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Introduction: Controlling and targeting release of bioactive compounds have a key role in improving their functional properties such as antioxidant and anti-disease activities. Encapsulation is one of the best methods for protection and controlling release of bioactive ingredients. Indeed, in this process, protection and controlling release of ingredients as core materials are performed by surrounding of them via variety of wall materials. Emulsions are most popular encapsulation systems that are classified in variety types such as single layer emulsion, multi-layer emulsion, doubleemulsion, and etc. Hydrophilic bioactive compounds can be loaded in inner aqueous phase of water in oil in water (W/O/W) double-emulsions. The stability of doubleemulsions is low due to presence of two interfaces in them.Applying a thermodynamically stable W/O emulsion (e.g., micro-emulsion) as a primary emulsion and using of complex biopolymers as emulsifier and stabilizer in outer phase of doubleemulsions can improve their stability (Dickinson, 2011; Boyer et al, 2012).Saffron bioactive compounds include crocin, picrocrocin, and saffranal are widely used for a variety of functional and healthy goals in food and pharmaceutical industries. These compounds have many different functions, including anti-carcinogenic, anti-oxidant, anti-depressant, anti-apoptotic, anti-tussive, anti-nociceptive, anti-inflammatory and anti-thrombotic properties (Moraga et al, 2004).In the present study, our main goal was kinetically evaluated release of crocin, picrocrocin and saffranal from inner phase to outer phase of doubleemulsion during 22 days storage by Zero order, Fist order, Higuchi, and Hixson-Crowell.Materials and method: Saffron was provided from Torbatheydariyeh farms, Khorasan-e-razavi, Iran. Sunflower oil and sodium azide were purchased from FRICO (Sirjan, Iran) and Sigma-Aldrich (St. Louis, USA), respectively. Whey protein concentrate (80% protein) and sorbitanmonooleate (span 80) were obtained from Sapoto cheese (USA) and Merck (Germany), respectively. Maltodextrin was obtained from Qinhuangdao starch Co. (DE 16-20, China) and citrus pectin with a degree of methyl esterification of 71.1% and galacturonic acid >65% was purchased from MP biomedical (Netherland). All other chemicals used in this study were of analytical grade.For extraction of crocin, picrocrocin and saffranal, a total of 10 grams of saffron sample was macerated in 150 mL of water in a glass bottle, covered with aluminum foil (to prevent direct exposure to light), and was placed in an incubator shaker (Kavooshmega, Iran) for 24 hours at 30oC. Then, this solution was homogenized (10000 rpm for 10 minutes, HeidolphSilentcrusher, Germany) for maximum extraction of saffron compounds. Finally, the extract was filtered under vacuum by using a Whatman No. 1 (11 mm) filter paper, and kept in the freezer at -18oC prior to any examination. ISO/TS 3632 procedure (2003) was used for the measurement of saffron compounds. The doubleemulsions were prepared in two-step:(a) Frist, primary W/O micro-emulsions were produced by two formulations: 60:30:10% and 62:33:5% of sunflower oil, span 80, and saffron extract, respectively. (b) Then, the W/O micro-emulsions was gradually added into the outer aqueous phase contains why protein concentrate (WPC)/maltodextrin or WPC/pectin/maltodextrin while blending by a homogenizer (12000 rpm for 5 minutes at 10oC, HeidolphSilentcrusher, Germany) and then these coarse emulsions were further emulsified using mentioned homogenizer (15000 rpm for 8 minutes at 10oC). All doubleemulsions were composed of 25% primary emulsion and 75% outer aqueous phaseDroplet size of doubleemulsions after one day and 22 days storage weremeasured using Zetasizer (Malvern Instruments, Worcestershire, UK).The released components in the outer aqueous phase were measured by evaluation of encapsulation efficiencyof the ratio of crocin, picrocrocin, and saffranalat a specific time:E (%) = 100- (C2×100/C1) (1)Where C2 is the percentage of crocin, picrocrocin and saffranal in outer aqueous phase and C1 equals to the percentage of compounds in inner aqueous phase.C2 is a released into outer aqueous phase relative to the total amount present in the outer aqueous phase if all compounds were released (M ∞).The viscosity of emulsions was measured using a programmable viscometer (model LVDV -II + Pro, Brookfield Engineering Laboratories, USA) and by a ULA spindle.The released are kinetly evaluated by Zero order, Fist order, Higuchi, and Hixson-Crowell.The experiments were all carried out in triplicate. The collected data were analyzed by one-way ANOVA; the means were compared by the Duncan's multiple range tests at the 5% level through SPSS version 21 (IBM, USA).Results and Discussion: As shown in fig. 1, the droplet size of produced W/O micro-emulsions were lower than 200 nm. In fact, these droplets are water droplets containing bioactive compounds of saffron dispersed within oil phase that surrounded with Span 80 (Fig. 2).Also, it was found that by increase of saffron extract (from 5% to 10%) as dispersed phase in W/O micro-emulsions, droplet size and poly-dispersityindex (PDI) weresignificantly (P< 0.05) affected (Table. 3).As shown in table. 4, crocin, picrocrocin, and saffranal had a same release trend, but the release rate of crocin was lower than saffranal and picrocrocin. As regard to R2, SSE, and RMSE from kinetic modeling in table. 5, the firstorder was a best model for release of crocin, and zero order was a best model for release of picrocrocin and saffranal. Also, kinetic date of release showed that the high release of crocin, saffranal, and picrocrocin was observed by increasing the dispersed phase content of primary W/O micro-emulsion and also it was found that WPC/pectindelayed the release of encapsulated ingredients more than single WPC (Table. 5). Indeed, the using of complex biopolymers as the external binary film of doubleemulsions causes a resistance to release for inner compounds (Dickinson, 2011).As shown in fig. 3, the viscosity of doubleemulsions stability with WPC/pectin complex was higher than doubleemulsions stabilized by only WPC. This can confirm the higher stability of stabilized doubleemulsions with complex biopolymers (Olivieri et al, 2003).
