| Pot-roast egg, as a kind of easy egg products, is the egg cooked in water with the addition of seasonings and fragrants, vacuum-packed, sterilized. Pot-roast egg, as a kind of delicious and convenient egg product, with special flavor, taste and convenience, come to be one of the most important ready-to-eat foods on family dinner table and outdoor travels. At the present, studies on the pot-roast egg were mainly about the formula composition and processing. Changes in quality during the processing and storage were studied very little. Changes in nutritions and volatile flavour compounds before and after processing had not been reported.The study about pot-roast egg was focused on changes in qualities during the processing and storage including the nutrious compounds, physical and chemical indicators, texture parameters, sensory quality, volatile flavour compounds and microbe indicators. The main conclusions were as follow:1. The optimal prescription of marinade consisted of 2.5% salt,3% sugar,2% soy sauce,4% fist kind fragrant,4% second kind fragrant,0.4% third kind fragrant,1.0% caramel (or 0.3% monascus),0.3% monosodium glutamate (MSG).2. The effects of pre-cooking (HTST, LTLT, BR) on quality of egg:Pre-cooking had no significant influence on the basic nutritions of egg (p> 0.05). L* value, hardness and chewiness in egg white and yolk in BR were significantly lower than that in LTLT and HTST group. The highest L* value (89.76) of egg white was shown in HTST group. L* value of egg yolk in LTLT and BR group were 82.32 and 83.54, which were significant higer than that in BR(58.96) (p< 0.05). Egg white and yolk in HTST had the highest chewiness 360.22 g and hardness 355.67 g. PUFA in HTST was 17.32%, higher than others, but lower than control by 2.47%. HTST was choosed as pre-cooking treatment because the samples in HTST group had better color and luster, appropriate hardness, cohesiviness, chewiness, and less loss in amino acids and fatty acids.3. During the processing of boiling, marinating and drying, water content in egg white and yolk decreased gradually from about 84% and 50% to 79% and 47%. pH in egg white decreased from about 9.0 to 7.8, pH in egg yolk had a smaller variation range from 6.3 to 6.7. Free fatty acid, amino nitrogen and TBA value increased. Hardness, chewiness of egg white increased gradually from about 650 g and 500 g to above 1300 g and 900 g, on the contrary, hardness, cohisiviness and chewiness of egg yolk reduced to about 450 g, 0.6 and 200 g. Sensory values increased then decreased when dried more than 90 min. The process parameters were:boiled at high temperature (97±2℃) for 2-3 h, marinated for 24 h, dried at 60℃for 60 min.4. The determined results of new processing pot-roast egg. Water content:egg white 79.12%, yolk 48.08%; pH values:egg white 6.83, yolk 6.35; salt content:egg white 1.73%, yolk 1.10%. Ca, Na, K, Zn, Mg Cu in total egg were 48.27mg/100g, 329.75mg/100g,71.02mg/100g,1.34mg/100g,9.15mg/100g and 0.21 mg/kg respectively. Pb was not detected. Compared with control, Na, Mg, Zn and total ashes contents of pot-roast egg were siginifantly higher (p< 0.05), whereas, the K content was significantly lower than that of control (p< 0.05).87 species of volatile flavour compounds were identified from pot-roast egg by SPME-GC-MS. They are mainly alkene, aromatics, aldehydes, ketones, etc., and more than 60% were from added seasonings. The products had nutritions, special taste and flavouring.5. The pot-roast eggs were sterilized by anti-pressure high temperature sterilization, combine sterilization and microwave sterilization, then were stored at room temperature 25℃. The T-VBN value, TBA value and total bacteria count were all gradually increased as the extension of storage time. Sensory value decreased totally. The effects of the three kinds of sterilization in order were:Anti-pressure high temperature sterilization> combine sterilization> microwave sterilization. High-temperature sterilized and combine sterilized samples stored at 25℃for 165 days were still safe and all indicators met national standards, however, the shelf life of microwave sterilized samples was just 60 days. |
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