Preparation Of The Edible Film Made From Red Okra Pectin-fennel Essential Oil And Its Bacteriostatic Effect On The Fresh-cut Pineapple

Red okra(Hibiscus coccineus(Medicus)Walt)is widely cultivated in China,but most research focus on cultivation techniques,cross-breeding,etc;there is little research on applying it in food processing.Red okra is rich in protein,amino acids,flavonoids,trace elements and pectin.This study aims to optimize the extraction process of red okra pectin and prepare edible composite film with glycerin as a thickener and fennel essential oil as a bacteriostatic agent.Based on the optimized process,the bacteriostatic effect of the edible composite film on fresh-cut pineapple was determined.The main research results of this study are as follows:1.The extraction parameters of red okra pectin were determined: the ultrasonic method assisted with ammonium oxalate was used to extract pectin with red okra as raw material.The ultrasonic power,extraction time,addition of ammonium oxalate and material-liquid ratio were regarded as the factors,and the pectin yield was used as the evaluation index.The extraction process was optimized by the response surface experiment and the results showed that the effect of those factors on the extraction yield was in the order: addition of ammonium oxalate > extraction time> ultrasonic power> material-liquid ratio.The optimum process condition was: ultrasonic extraction power of 380 W,extraction time of 25 min,ammonium oxalate addition of 3.5%,and ratio of material-liquid of 1:34.Under this condition,the extraction yield of red okra pectin was 18.16%.2.The optimal film-forming process was determined: the scores of TS and EB were used as the evaluation index and the effects of various factors on the properties of the edible film were investigated by single factor test and response design test.The optimal film-forming process was as follows: 6.3% red okra pectin,5.84 mL glycerin and drying temperature 55.7°C.The total score of the film under this condition was 39.7.3.The antibacterial effect of red okra pectin-fennel essential oil compound edible film on fresh-cut pineapple was studied: based on the optimal preparing process of the edible film,the effect of fennel essential oil addition on the film bacteriostatic activity for fresh-cut pineapples was determined.The fresh-cut pineapple was coated with an edible film under aseptic conditions,and the total number of colonies and the number of molds were measured after a certain period of time.The PE film group was added as the comparison.The results showed that both aerobic bacterial counts and the number of molds in the experimental group were lower than those in the control group and the PE film group.In addition,the bacteriostatic effect is proportional to the addition of fennel essential oil.However,the essential oil aroma could mask the fruit aroma;60?L/mL fennel essential oil was added to the edible film for the fresh cut pineapple,which film bacteriostatic action was best...