Encapsulating fish oil by spray drying with an adequate wall material was investigated to determine if stable powders containing emulsified fish-oil-droplets can be formed. In particular, the dextrose equivalent (DE) of maltodextrin (MD) affects the powder structure, surface-oil ratio, and oxidative stability of fish oil. The carrier solution was prepared using MD with different DEs (DE = 11, 19, and 25) and sodium caseinate as the wall material and the emulsifier, respectively. The percentage of microcapsules having a vacuole was 73, 39, and 38% for MD with DE = 11, 19, and 25, respectively. Peroxide values (PVs) were measured for the microcapsules incubated at 60 °C. The microcapsules prepared with MD of DE = 25 and 19 had lower PVs than those prepared with MD of DE = 11. The difference in PV can be ascribed to the difference in the surface-oil ratio of the spray-dried microcapsules.

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A simple method was developed for determination of the oil content in spray-dried microcapsules by dissolving the microcapsules in N, N-dimethylformamide (DMF). Powders containing flaxseed or fish oils were prepared by homogenization and subsequent spray dr ying to form coarse and fine emulsions. Sodium caseinate (SC) and maltodextrin (MD) were used as an emulsifier and wall material, respectively. The oil contents in the powders were quantified using a thin-layer chromatography-flame ionization detector after hexane extraction; the results agreed well with the initial oil contents on a dry basis in the feed emulsion, regardless of the oil-droplet size in the powders. The fatty acid compositions of the flaxseed and fish oils in the powders were obtained without an extraction process, using the proposed method. After dissolving the microcapsules in DMF, the peroxide value (POV) of the encapsulated oil was determined using the acetic acidchloroform method. Although SC, MD, and DMF slightly increased the POV, the ef fect of the increase on the POV was not significant. The proposed method therefore enables easy and rapid estimation of the oil content, fatty acid composition, and POV of an encapsulated oil. ◇◇◇ Original paper ◇◇◇ IntroductionMicroencapsulation has been widely used for the preparation of powdered edible oil products, because it can provide prolonged shelf-life by protecting oils with appropriate encapsulating substances such as milk protein, dextrin, modified cellulose, gelatin, plant gums, and modified starch [1-3]. Microencapsulation is used in the food industry to protect marine-based fish and fish oils, which are rich in n-3 polyunsaturated fatty acids (PUFAs) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These PUFAs are well known to have a variety of health benefits such as anti-inflammator y, anticancer, antioxidant, and insulin-sensitizing effects [4-6]. In the food industry, the most widely used techniques for encapsulating lipophilic compounds are based on the production of an oil-in-water emulsion, followed by either spray drying, freeze drying, molecular inclusion, enzymatic gelation, or coacer vation. Among the various techniques, spray drying is the most common, because of its low cost and availability of equip-ment. The advantages of spray drying also include continuous operation, with the possibility of automatic control and constant product quality at high throughput rates. The disadvantage of this technique is the hightemperature conditions necessary for drying, and exposure to air. Moreover, during drying, some of the product may adhere to the surfaces of the capsules, resulting in potential oxidation of the final food products. In order to obtain a high loading efficiency, even if the wall material is suitable, optimal spray-dr ying conditions must be used [7-9]. The main factors in spray drying that should be optimized are the inlet and outlet air temperatures.The final product is evaluated in terms of loading efficiency [10-12], particle size [13-15], reconst...

The effect of the size of oil droplets on the oxidative stability of flaxseed oil in spray-dried powders was investigated. Maltodextrin with a dextrose equivalent of 25 was used as a wall material, and sodium caseinate and transglutaminase-polymerized sodium caseinate were used as emulsifiers. The oxidative stability of flaxseed oil encapsulated in the spray-dried powders was evaluated using lipid oxidation and conductometric determination tests at 105 °C. The powders containing larger oil droplets exhibited higher surface oil content after spray drying, and higher peroxide value and conductivity after storage at 105 °C. Removal of the surface oil from the powders by washing with hexane significantly decreased the conductivity. The results indicated that the surface oil of the spray-dried flaxseed oil powders affected the oxidation stability.

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