Studies On The Development Of Low-sugar Preserved Apples And Microbial Stsbleility In Products

Since about 1990t there has been a focus on developing low-sugar preserved apples. At present the main difficulties in processing low-sugar preserved fruits is to enhance sensory properties If the products and lengthen shelf life. The experiments were carried out with apple based on vaccwm-permeation technique. A method of reducing sugar content of the preserved apples was proposed for the first time. The factors affecting the sensory properties of the product such as, transparency, pulmpress were examined, and the principle and methods which preserve low-sugar preserved apples were investigated. The principle and methods which preserve low-sugar prcscrved apples were investigated. The results were al follows:1. Substitution polydextroses for sucrose or glucose in processing preserved apples could reauce suguar content in product in desked level. The technological processing were as follows: Apples-removing peel and core- cutting into pieces -dipping in permeating solution under vaccum--inactiviating enzyme - drying products.2. The major factors affecting vaccum-permeation, such as osmosis dehydration pretreatment, vaccum-permeation times,, the main parameters of vaccum-permeation were dealt with. A mathematical model was extablelished which evaluate the amout If permeating solution trafer to apple pieces.3. Adding hydrophilic colloid, particular in pectin to apple pieces enhanced the sensory properties If the products.4. Factors of polydextroses content, pectin content and water content in product proved to have significant effect on plumpness of products.5. The drying time was shortend, the sensory quality If the products was enhanced and vitamin c retention was high by microwave-drying in comparison with air-drying.6. The effect If different carbonhydrate and hydrophilic colloid on reduction of aw was investigated, low-sugar preserved apple with Aw can be calculated as follows:Y =0.76-0.01145X,+0.0897X2+0.1082X,-0.048X,2 where Y is Aw, X, and X, is polydextroses and pectin content, X3 is water content in product, respectively.7. Aw had significant effect on microbial stableility in low-sugar preserved apples. The microbe in products with 0.65-0.70 Aw remained dormant during storage at room temperature, while molds and yeast in product with 0.75-0.80AW reproduced quickly during storage, which would affect the quality of products.8. Microwave had better killing effect on molds and yeast than heat treatment and initial numbers If molds and yeast should be comtrolled under low level. After microwave irradiation, storage experiments on products with 0.8AW were conducted.9. Compared with 100% air packing, vaccum packing could inhibit microbe reproduction, particular in molds.