The Process Optimization Of Bamboo Shoots Soft Canned And Freeze-dried Bamboo Shoots

Bamboo shoots are delicious traditional food of high nutritional value and edible value which have been consumed for centuries. Due to the aging of fresh bamboo shoots fleshy fibers easily rot, intolerance storage, mainly made of bamboo shoots soft canned or dried bamboo shoots to use for now. The majority of products marketed bamboo shoots soft canned added chemical preservatives, and the poor quality of dried bamboo shoots, browning serious. In order to solve these problems, in this study, a commercially available fresh bamboo shoots as raw material, the response surface experiments, uniform tests and orthogonal tests were used to optimize processing conditions of bamboo shoots soft canned and freeze-dried bamboo shoots. Processed three products as preservative-free bamboo shoots soft canned, bamboo shoots soft canned contained natural antibacterial agent and freeze-dried bamboo shoots. The main research results were as follows:1. The key processes optimization of preservative-free bamboo shoots soft canned. Investigated the effects of precooked time, pH value, sterilization temperature and sterilization time these four factors on the processing of preservative-free bamboo shoots soft canned, the aerobic plate count (CFU/mL) in (55±2)℃ incubator after placed 15d as an indicator, determined the optimum conditions for each single factor. Based on this, the response surface was used to optimize process, the optimum processing conditions were precooked time 30min, pH value 4.5, sterilization temperature 125℃, sterilization time 25min. The aerobic plate count of preservative-free bamboo shoots soft canned measured under these conditions was 13CFU/mL.2. The natural antibacterial formulation optimization of bamboo shoots soft canned. Complexed R-polysaccharides, polyphenols, ε-polylysine these three kinds of natural antibacterial agent, the aerobic plate count (CFU/mL) in (55±2)℃ incubator after placed 20d as an indicator, the uniform test was used to optimized the best antibacterial agent formulation. The best antibacterial agent formulation was R-polysaccharides 0.02%, polyphenols 0.035%, ε-polylysine 0.05%. The aerobic plate count measured under these conditions was 1CFU/mL.3. The shelf life prediction of two kinds bamboo shoots soft canned. The optimum conditions were used to process two kinds of bamboo shoots soft canned, the aerobic plate count (CFU/mL) and sensory evaluation as indicators, the Q10 value model method was used to predict the shelf life of two kinds bamboo shoots soft canned. The final predicted results were as follows:shelf life of preservative-free bamboo shoots soft canned at 35℃ was 70d, at 45℃ was 30d, at 25℃ was 160d; shelf life of bamboo shoots soft canned contained natural antibacterial agent at 35℃ was 110d, at 45℃ was 45d, at 25℃ was 265d. According to these, added natural antibacterial agents could extend shelf life effectively.4. The determination of shelf life qualities changes of two kinds bamboo shoots soft canned. Compared two kinds of commercially available products with two kinds of bamboo shoots soft canned which processed in this study, determined their solid content, pH value, protein content and soluble sugar content about 150d within the shelf life, observed the trend indicators and sensory evaluation of bamboo shoots soft canned within the measurement period. It can be concluded that:150d within the shelf life, the solids content of bamboo shoots soft canned remained unchanged, other indicators showed a gradual downward trend; and the solid content, pH value, protein content and soluble sugar content of two bamboo shoots soft canned processed in this study were better than commercial products, sensory score slightly higher than the commercial products, had certain market competitiveness.5. The process parameters optimization of freeze-dried bamboo shoots. Investigated the effects of citric acid concentration, blanching time, pre-freezing time and drying time these four factors on the processes of freeze-dried bamboo shoots, the rehydration rate (min-1) as an indicator, determined the optimum conditions for each single factor. Based on this, the orthogonal test was used to optimize and validate the three factors which have greater impacts. The optimum processing conditions were citric acid concentration 0.1%, blanching time 6min, pre-freezing time 4h and drying time 20h. The rehydration rate measured under these conditions was 0.393min"6. The qualities comparison about freeze-dried bamboo shoots and hot air dried bamboo shoots. Compared the freeze-dried bamboo shoots processed under optimum conditions with commercial hot air dried bamboo shoots about their qualities, it can be concluded that:the moisture content of freeze-dried bamboo shoots was 5.84%, rehydration ratio was 7.59, rehydration rate was 0.330 min-1, soluble sugar content was 48.39 mg/g, protein content was 7.84mg/g; the moisture content of hot air dried bamboo shoots was 9.57%, rehydration ratio was 2.24, rehydration rate was 0.062 min-1, soluble sugar content was 106.46 mg/g, protein content was 4.73mg/g. Above these, all the indicators of freeze-dried bamboo shoots were significantly better than the hot air dried bamboo shoots, and freeze-dried bamboo shoots have better rehydration effect and storability.