Browsing by Subject "microencapsulation"

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  • Kamlang-ek, Pimwalee (Helsingfors universitet, 2012)
    The literature survey reviewed principles of oxidation of edible oils, adverse effects of lipid oxidation and analysis of volatile oxidation products by SPME-GC-MS. The main aim of the experimental research was to study the influence of relative humidity (RH) on the release of volatile oxidation products from spray-dried emulsions with natural and cross-linked casein as emulsifier. The release of volatiles was determined by SPME-GC-MS. The sub aims were to study the effects of stabilization time at specific RHs, of temperature and agitation speed during the SPME extraction. The spray-dried emulsions were oxidised at 40oC in order to reach a certain level of oxidation. Next, the powders were stabilised under five RHs (0%, 11%, 33%, 54% and 75%) for one or two weeks in order to observe the effect of the RH and the stabilisation time on the release of volatiles. After adjusting the RHs, volatile compounds were analysed by SPME-GC-MS. The following SPME extraction conditions were tested: C1: temperature 40oC, agitation speed 250 rpm, C2: 50oC, 250 rpm, C3: 40oC, 500 rpm and C4: 50oC, 500 rpm. Identification of the compounds was carried out by matching their MS spectra with the NIST database. Altogether 45 volatiles released from the powders could be identified, and 18 of them were found in most samples. RH had an important effect on the release of volatiles from the encapsulated samples. The highest release was always observed at 11% and 33% RH, whereas the lowest release was found at 0% and/or 75% RH, depending on the SPME extraction conditions. The stabilisation time did not have a significant effect on the release of volatiles in most RHs. During the SPME extraction step, elevation of the temperature from 40oC to 50oC, as well as the agitation speed from 250 rpm to 500 rpm, facilitated higher release. However, the effect of temperature was greater than that of agitation speed. Although it was suspected that cross-linking of sodium-caseinate would enhance retention of volatiles, our experiment showed greater peak areas of most volatiles from the cross-linked samples than from the natural ones. By controlling the SPME parameters, it was possible to obtain repeatable volatile compound results. The SPME-GC-MS method applied in this study can be reliably used to analyse volatile oxidation products from spray-dried emulsions. Only at very low or high RH the release of volatiles may differ from samples stored at 11% -54% RH.
  • Selmer, Ilka; Karnetzke, Julia; Kleemann, Christian; Lehtonen, Mari; Mikkonen, Kirsi S.; Kulozik, Ulrich; Smirnova, Irina (2019)
  • Tarmi, Siina (Helsingfors universitet, 2017)
    The scope of the literature review was to define the process for oil-in-water emulsion formation and the important properties of the emulsions which are suitable for microencapsulation. The aim of this study was to determine how whey protein isolate together with maltodextrin affects the properties of the emulsion. Camelina oil and black currant seed oil were used as core materials. The wall materials used were: maltodextrin (MD) and whey protein isolate (WPI). Six different wall systems consisting WPI in combination with MD at various ratios (1:1, 1:3 and 1:9) were used. In premilinary tests the emulsions were characterized for temperature, creaming index, apparent viscosity, flow behavior index, flow consistency index, droplet size (D4,3 zetasize,), droplet size distribution (PDI, span) and zetapotential. Droplet size and droplet size distributions were measured by a laser light scattering using a Zetasizer and by laser light diffraction instrument, Mastersizer 2000/3000. Oil droplet size was also measured with light blockade using a PAMAS. Rheological properties were characterized with rheometer. In actual test the emulsions were characterized for time (foam removal), temperature, droplet size (D10, D50, D90 ja D4,3), apparent viscosity, flow behavior index and flow consistency index. First degree polynomial was fitted with PLSR to the results. Statistical significances of regression coefficients were analyzed with t-test. In premilinary tests all the emulsions were stable during storage at 25 °C after 24 h. pH and zetapotentials which were all lower than -35 mV refer to good stability of emulsions. Change in droplet size and droplet size distribution was observed. Increasing maltodextrin concentration decreased droplet size (D4,3) and droplet size distribution width (PDI) when measuring by Mastersizer and Zetasizer. Apparent viscosity of the emulsions decreased by increasing maltodextrin concentration. PLS-regression showed that there were statistically differences between wall materials and temperatures, droplet size, size distribution and apparent viscosity. There were also statistically differences between oil and droplet size measured by PAMAS. In actual tests apparent viscosity of the emulsions decreased by increasing maltodextrin concentration. Increasing maltodextrin concentration also decreased the time of foam removal. PLS-regression showed that there were statistically differences between wall materials and temperatures after homogenization, time (foam removal), flow consistency index and apparent viscosity. There were also statistically differences between oil and temperatures, flow behavior index and droplet size distribution width. Whey protein isolate together with maltodextrin affect mostly to apparent viscosity of emulsions.
  • Moilanen, Henna (Helsingin yliopisto, 2020)
    Lipid oxidation presents one of the most important challenges for the processing and storage of edible oils by lowering the shelf life, nutritional value, and organoleptic properties of oils. Microencapsulation is a process where oil droplets are coated within a wall material matrix, and it offers a suitable solution to protect edible oils against oxidative deterioration. This study aimed at exploring the effects of wall material composition and relative humidity (RH) on the potential of microencapsulation to protect camelina and blackcurrant seed oils against lipid oxidation. Camelina and blackcurrant seed oils were emulsified using whey protein isolate (WPI) and maltodextrin (MD) as wall materials in 1:1, 1:3, and 1:9 ratio, and the total solids content and wall-to-oil ratio were kept constant. Microencapsulation was conducted by spray drying, and various parameters were analyzed, including emulsion viscosity, water sorption properties, and the surface oil content of microencapsulated powders. The powders were conditioned at 11% and 44% RHs at 21 °C, after which the sample vials were closed to maintain constant water content. The oxidative stability of the conditioned microencapsulated powders was analyzed over 10 weeks of accelerated storage conditions at 40 °C by measuring the volatile secondary lipid oxidation products every two weeks by headspace-solid phase-microextraction-gas chromatography-mass spectrometry method. The results showed that the best oxidative stability during the storage period was obtained by WPI-MD 1:1 ratio in both of the microencapsulated oils, even though this wall material composition resulted in the highest surface oil content and the lowest encapsulation efficiency. In blackcurrant seed oil powders, the water content obtained at 44% RH seemed to provide better protection against lipid oxidation than that of 11% RH. Regarding camelina oil powders, water content obtained in different RHs did not seem to affect the oxidative stability of the powders. However, based on the peak areas of volatile compounds detected at week 10, the water content obtained at 44% RH might provide better storage stability for camelina oil containing powders in long-term storage than that of 11% RH.