Study On The Effect Of Ice-temperature Storage On Quality Of Red Raspberries

Raspberries, as a kind of berries fruit, has taken more people’s attention because of (?) nutritional value. Its fresh fruit contains a variety of vitamins, fruit pectin, superoxide dismutase(SOD), and potassium, phosphorus, iron, zinc and other minerals, is known as "red b(?)y""the fruit of life","the bane of cancer". But raspberry has thin skin, tender organization, and high respiratory intensity, prone to mechanical damage, sol day will lose the goods value under normal temperature. Therefore, the research of preservation technology of raspberry has real economic significance.In order to extend the shelf life of the red raspberry, this paper take the red raspberry as material and study on controlled freezing-point storage of quality.Design four groups of experiments:ordinary cold group (control group), direct ice-temperature storage group, ice-temperature+CA group, ice-temperature+CA group, ice-temperature+natamycin group, first,study the feasibility of the ice-temperature storage;then, study the effect of different ice-temperature treatment on storage quality of raspberries. In sensory evaluation, titratable acid, soluble solids, respiratory intensity, ethylene formation rate as the measurement indicators, combined with the biochemical indicators malondialdehyde, polyphenol oxidase, peroxidase and catalase for comprehensive analysis.In this paper, the main research results are as follows:(1) By determinating the freezing point of raspberries of the experiments,it’s found that raspberry’s freezing point is different as its varieties is different.Here "the autumn red" freezing temperature is-1.2℃, and the freezing point of "Heritage" is-1.1℃. As a result, the ice house temperature is set to-0.9±0.4℃(2)"Autumn red" is storaged in cold and ice-temperature condition, to study the feasibility of ice-temperature storage of raspberries. The results show that compared with the cold storage, ice-temperature storage further reduces the raspberry’s respiratory metaboiism rate, delayed the senescence of the fruit, and extend its time to keep good quality; And has obvious restrain effect on the decay rate, mildew rate, MDA content rose,(?) slgnificantly inhibit titratable acid, TSS content decreased, the difference of both stetage way for the influence of pH is smaller. At the same time, ice-temperature storage improves the activity of catalase (CAT), decreased the activity of polyphenol oxidase (PPO) of raspberries, so as to delay the aging of the raspberry. Illustrating that ice-temperature (?)pberry fruit preservation, the effect is much better than ordinary(?)(?) is packaged with PE bag at0.03,0.04,0.05mm thickness,(?) conditions with the blank group, it was conducted to investigate the effect of ice-temperature combined with modified atmosphere storage on quality of raspberry.Results showed that:compared with direct ice-temperature storage,ice-temperature combined with modified atmosphere storage more effectively delayed the raspberries’titratable acid, TSS content decreased,it further delay the increase of MDA content, reduced the PPO activity, improve the activity of POD, CAT of raspberry, At the same time, gas packing also inhibit the respiratory intensity, ethylene generation rate. Explaining that ice-temperature combined with modified atmosphere is good to keep the quality of raspberry fruit, different thickness of the PE bag also have different effect, the thickness of0.04mm PE bag effect is best.(4) Spraying "Heritage"with different concentrations of natamycin,air-dried and storage in ice-temperature conditions with the blank group, it was conducted to investigate the effect of ice-temperature combined with natamycin treatment on quality of raspberry.Experimental results show that:compared with ice-temperature storage, natamycin treatment has effect on the growth of the mold on the surface of raspberry, among them,800ppm concentrations of natamycin treatment has the best bacteriostatic effect.starting from the12days of storage, has significant difference (p<0.05) with the direct ice-temperature group.natamycin treatment also improves the PPO,POD and CAT activity of raspberry,increase the defensive function of raspberry fruit.different concentration produce different effect,the concentration of800ppm natamycin over to improve enzyme activity in terms of best effect.But raspberry’s appearance quality deterioration quickly after natamycin treatment. Illustrating that at ice-temperature condition,the effect of natamycin treatment on storage is not obvious promotion, may ice-temperature conditions on the storage effect is greater than the influence of natamycin treatment.