Biocapsulation of wheat germ oil with Saccharomyces cerevisiae cell and characterization of biocapsules

Wheat germ, which is a by-product of the flour milling process, contains up to 11% oil. In addition to being a very rich source of valuable phytochemicals such as phytocysterols, policosanols, thiamine, riboflavin and niacin, germ oil has the highest α-tocopherol content among known vegetable oils. It is also a good source of valuable ingredients such as oleic and linoleic acid, which show strong bioactivity, which are unstable to environmental conditions and can be easily oxidized. Due to its low stability, it is difficult to control in food production processes and storage processes and consequently its use is very limited. For this reason, it cannot be used sufficiently in human nutrition. The aim of this study is to solve the oxidation problem by encapsulating germ oil using Saccharomyces cerevisiae cells and to achieve controlled release. Within the scope of the study, after determining the fatty acid composition and nutritional properties of germ oil used as the core material, encapsulation was produced. Plasmolized (P), non-plasmolized (n-P) and living (C) forms of S. cerevisiae yeast cells were used in the encapsulation process. Germ oil: different mass ratios of yeast cell (0.25, 0.5, 1 and 2) water and ethanol production media were used. Among the formulations, the highest encapsulation efficiency was determined in the formulation using P as the shell material, at a mass ratio of 0.25, and using water as the production medium. The morphological structures of the oil-loaded encapsules were examined by scanning electron microscopy (SEM) and it was observed that the spherical structure was obtained in the encapsules using P shell material. In the in vitro release profile in environments mimicking the human digestive system (mouth, esophagus-stomach, duodenum and small intestine), it was determined that P encapsules could be used as suitable wall material to transport germ oil through the gastrointestinal tract to the intestines. In addition, in the Fourier transform-infrared (FT-IR) analysis, it was determined that the germ oil was successfully encapsulated and the oil was imprisoned in the capsules. The oxidative stability of the samples obtained before and after encapsulation was measured by the Ransimat technique (100°C temperature and 10 L/h air flow rate) and the accelerated oven test performed at 60°C for 24 days. By encapsulation of germ oil in P shell material, it becomes more resistant to oxidation, both by ransimate (3.39 hours to the highest induction period) and oven test (lowest peroxide number: 9.19±1.41 meq O2/kg oil and the lowest p-anisidine value: 34.42±1.55) was determined. As a result, the use of yeast cells in increasing the oxidative stability of germ oil is being investigated as a new approach. The obtained study results indicate that plasmolized yeast cells protect germ oil against oxidation under adverse conditions. Keywords: germ oil, yeast cell, encapsulation, oxidation