Fatty acids characterization and oxidative stability of spray dried designer egg powder.

BACKGROUND: Designer eggs (DEs) have gained positive importance in maintaining cholesterol level, triglyceride profile and protection towards cardiovascular diseases due to the presence of essential fatty acids (EFAs) such as omega-3 (or) n-3 fatty acids. However, extreme heat conditions effect the quality as well as quantity of EFAs during the production of designer egg dried powder (DEDP). Therefore, the main mandate of research was the development of DEDP and determination of spray drying conditions impact on fatty acids composition of DEDP samples. METHODS: The DEs were produced, collected, de-shelled, homogenized and diluted before spray drying to get fine powder. The spray drying of DEs was carried out using a laboratory spray drier. An experimental design was used for the drying parameters, where the inlet air temperature was varied (160, 180 and 200 °C), feed flow rate (200, 300 and 400 mL/hr), atomization speed (16,000, 20,000 and 24,000 rpm) and outlet air temperature (60, 70 and 80 °C) at different levels. For convenience of experimental design coding was used. The DEDP was collected in a single cyclone separator and was stored after packaging for consecutive 2 months at 25 °C and 4 °C, respectively. The powder yield was calculated from the collected dry mass in the collecting vessel divided by the processed whole egg diluted matter. The total lipids of DEDP samples were determined gravimetrically. The esters of fatty acids in each sample were prepared and analyzed through Gas Chromatograph apparatus. The oxidative stability of DEDP samples was estimated by following standard procedure of peroxide value. RESULTS: The powder yield of DEDP as a result of different operating conditions was found in the range of 30.06 ± 0.22 g/500 mL to 62.10 ± 0.46 g/500 mL DEs sample. The decreasing trend in moisture content (4.4 ± 0.16% towards 4.0 ± 0.09%) and total fat content (45 ± 0.65 g/100 g towards 41 ± 0.35 g/100 g) in DEDP samples was observed with increased inlet and outlet temperature while fat content increased at high feed flow rate and atomization speed. In this study, loss of PUFAs in DEDP samples was followed due to their active role regarding to human health. For alpha-linolenic (ALA) fatty acids, maximum value at 4 °C observed was 127.32 ± 0.27 mg/50 g egg and 124.43 ± 0.32 mg/50 g egg while the minimum value observed for ALA was 100.15 ± 0.09 mg/50 g egg and 97.15 ± 0.06 mg/50 g egg after 30 and 60 days storage, respectively. The significant decrease trend for eicosapentaenoic (EPA) fatty acids values from 11.78 ± 0.31 mg/50 g egg to 2.18 ± 0.14 mg/50 g egg at 25 °C under spray dried conditions of inlet air temperature (180 °C), feed flow rate (300 mL/hr), atomization speed (24,000 rpm) and outlet air temperature (80 °C) after 60 days storage period was noted. The docosahexaenoic (DHA) fatty acids value in DEDP was decreased from 15.49 ± 0.79 mg/50 g egg (0 day) to 10.10 ± 0.64 mg/50 g egg at 60 days (4 °C) and same decreasing trend was observed at 25 °C. The decreasing order for total omega-3 fatty acids retention in DEDP during storage intervals was found as 162.33 ± 1.64 mg/50 g egg > 158.61 ± 1.53 mg/50 g egg > 148.03 ± 1.57 mg/50 g egg (0, 30 and 60 days stored at 4 °C) and 162.33 ± 1.64 mg/50 g egg > 151.56 ± 1.54 mg/50 g egg > 135.89 ± 1.62 mg/50 g egg (0, 30 and 60 days stored at 25 °C). The peroxide value (PV) levels obtained in DEDP samples after 60 days were higher (0.78 ± 0.06, 0.81 ± 0.02 meq/kg O2) when compared to initial readings at 0 day (0.65 ± 0.04 meq/kg O2). The PV of DEDP samples reached their maximum peaks after 60 days at 25 °C. The increasing order showed that lipid oxidation increased with storage. However, the overall PV never exceeded the limit of 10 (meq/kg) considered as a threshold limit. CONCLUSIONS: Extreme hot conditions (> 180 °C) of spray dryer reduce the quality of designer egg dry powder. Extreme conditions assist PUFAs loss and decrease in storage stability due to high lipid oxidation.