Development Of Freeze-dried Carrot Slices With Probiotics

Probiotics are one of the important functional factors in functional foods,they were widely used in dairy products,snacks,candies,fruit and vegetable juices,soy milk,kimchi,etc.Carrots are rich in functional active substances such as ?-carotene and polysaccharides.Therefore,it has high nutritional value and health benefits,and has the reputation of "Oriental Ginseng".This subject researched freeze-dried carrot slices with probiotics.The main research results are as follows:1.Carrots were fermented with jujube juice at 37? for 7 days,the effects of physical and chemical indexes and nutritional components during the fermentation process of carrots were studied.The results showed that the content of ascorbic acid and carotene in the jujube juice group was significantly higher than that in the control group and the carrot group without jujube juice,which the content of ascorbic acid and carotene in the jujube juice group increased by 8.48 mg/100g(P<0.01)and 1.29 mg/100g(P<0.05)after 7 days of fermentation.the content of total phenol,total acid and the numbers of Lactobacillus plantarum in the jujube juice group were significantly higher than that in the control group and the carrot group without jujube juice(P<0.01).The content of polysaccharides and nitrite in the fermented group with jujube juice decreased,but there was no significant difference among 3 groups fermented carrots.Meanwhile,there was no significant difference in texture,color difference and p H values of carrots in three groups(P>0.05).The results of gas chromatography-mass spectrometry(GC-MS)and electronic nose analysis showed that the addition of jujube juice could reduce terpenes,increase ketones and aromatic hydrocarbons,and thus mask the original drug smell of carrot,and emit the unique flavor of fruit and vegetable fermentation.The results showed that jujube juice could improve the quality of fermented carrots by Lactobacillus plantarum to some extent.2.The fermented carrots from the previous chapter were freeze-dry to make carrot crisps.The results showed that the precool time had no significant effect on the moisture content,rehydration ratio,hardness,brittleness and color of carrot.The moisture content of carrot was5% after 8 h precool and 14 h drying.The rehydration ratio reached a maximum of 7.75 g/g.The brittleness is 6994.50 g,the hardness is 26855.29 g,and it has good crispiness and chewiness.There is no obvious change in color.The content of polysaccharides was the highest at 8 h,and the effect of drying time on the content of polysaccharides was not obvious.The content of ascorbic acid remained stable at different precool time,but decreased with increasing drying time.The total carotene content was stable in the process of pre-freezing and drying.The effect of pre-freezing and drying time on the viable bacteria count was very significant,and with the increase of pre-freezing and drying time,the viable bacteria count decreased gradually.Therefore,the freeze drying process of carrot slices was determined as the pre-freezing time of 8 h and drying time of 14 h.3.In order to increase the number of viable bacteria in carrot slices,the probiotic microcapsule technology was used to improve the activity of Lactobacillus plantarum.In this study,microcapsules of Lactobacillus plantarum(L.plantarum)were prepared by extrusion technique using sodium alginate(SA),sodium alginate-sodium caseinate(SA-SC)and sodium alginate-whey protein isolate(SA-WPI)as wall materials.The characteristics of microcapsules were also investigated.Results showed that the encapsulation yield of L.plantarum were 70.40 ± 2.80%,46.08 ± 2.50% and 42.72 ± 0.48% for SA-WPI,SA and SA-SC,respectively.Morphology and texture analysis showed that the microcapsules prepared by SA-WPI system presented more compact internal structure and higher resistance to external pressure.Fourier-transform infrared spectroscopy(FT-IR)and low field nuclear magnetic resonance(LF-NMR)analysis demonstrated that the hydrogen bonding ability and network structure of the SA were improved by the addition of WPI.The survivability of L.plantarum entrapped with SA-WPI system were improved during freeze-drying and simulated gastrointestinal digestion,remaining more than 8.20 lg CFU/g.Therefore,SA-WPI system as wall materials provided the best protection for microencapsulated cells in freeze-drying and simulated gastrointestinal digestion.Afterwards,SA-WPI microcapsules were applied to carrot fermentation.The results showed that the encapsulation of Lactobacillus plantarum would not affect the fermentation process,and it was not restricted in practical applications.4.In the process of storage,the water content of the above probiotic carrot slices increased,and the values of rehydration ratio,hardness,brittleness and brightness L*decreased,while the values of a* and b* did not change significantly.The color of the carrot slices became dark and the taste was soft,but they still had a crisp feeling.The contents of polysaccharide and ascorbic acid decreased significantly,which were 2.86±0.14 g/100 g and15.89±0.46 mg/100 g at 28 d,respectively.The decrease rate of total carotene content was low during storage,and the retention rate was still 80% at 28 d.The number of viable bacteria decreased gradually during storage,and the number of viable bacteria was 6.03±0.05 lg CFU/g at 28 d,which can meet the conditions of its full play of the role of probiotics.