| Forest berry is an important undergrowth resource with rich nutrition and unique flavor,but it is not easy to store and has strong seasonality,which makes many forest berries wasted and causes huge economic losses.Due to the particularity of geographical location and climate environment,Northeast China is very suitable for the cultivation and growth of small berries,and has become the main production and planting place of berries in China.Efficient use of berry resources under the forest can provide a scientific basis for better improving the transformation of forest economic benefits,which has important research significanceIn this experiment,a large number of strains were isolated from the natural fermentation broth of Hippophae rhamnoides,Physalis philadelphica,Rubus corchorifolius and Vaccinium spp.,the fermentation broth of rural sauerkraut,pickle and common probiotic powder.A total of 16 strains of Lactobacillus plantarum(Among them,6 strains were from probiotic powder,1 strain was from pickle fermentation broth,and 9 strains were from pickle fermentation broth),2 strain of Lactobacillus brevis and 1 strains of Lactobacillus coryneformis were obtained.Probiotics were screened according to three criteria:acid resistance,bile salt resistance,adhesion to intestinal wall cells and inhibition of harmful bacteria.The results showed that the strain H13 had the best acid resistance,and its survival rate was 92.7%in pH=2 MRS medium for 4 h.The worst acid resistant strain was S6,and the survival rate was only 40%.The strain with the strongest bile salt tolerance is S68,with a survival rate of 91.11%within 4 h in the MRS medium with a bile salt concentration of 0.2%.The strain with the weakest bile salt tolerance is S213,with a survival rate of only 7.61%.The strongest inhibitory effect on Staphylococcus aureus is H2,with an average inhibition zone size of 1.75 cm in diameter.Strains S13,S36,and S213 have no inhibitory effect on Staphylococcus aureus and do not produce a zone of inhibition.After screening out the unqualified strains,the probiotic strains are H2,H4,H8,H13,Z1,P1,S8,S45,S64,S65.The 10 probiotic strains selected in the pre-experiment were further screened through acid production characteristics,cholesterol degradation rate determination and taste and flavor evaluation experiments.The results showed that the strains H2,P1,Z1,and S64 had strong acid-producing ability,and the pH value of the acid-producing end point was lower,about 3.86.Strain H4,H13 poor activity,weak acid production,high acid production endpoint pH,5.34 and 4.55 respectively.After comparing the two cholesterol measurement methods,it is found that the ferric ammonium sulfate method is more suitable for the determination of samples in this experiment.In the cholesterol degradation rate determination experiment,it was found that each test strain had a certain ability to degrade cholesterol and the degradation rate was not much different.Among them,the strain with the strongest ability to degrade cholesterol was H4,and the cholesterol degradation rate was 56.50%.The strain with the weakest ability to degrade cholesterol is S65,with a cholesterol degradation rate of 51.10%.In the taste and flavor evaluation experiment,the fermentation flavor of strain H13 was the best,with a total score of 95 points.Strain P1 has the worst fermentation flavor,with a total score of only 50 points.S64 was selected to further explore its optimal fermentation temperature.Put an equal amount of strain S64 shaking culture solution into a fermentation bottle consisting of 100 g berries(the ratio of berries is Hippophae rhamnoides;Physalis philadelphica:Rubus corchorifolius:Vaccinium spp.=1:1:1:1:1)and 200 mL sterile water.Regularly detect the pH value of the fermentation broth to determine the fermentation rate of the juice at different temperatures.The results showed that the optimum fermentation temperature range of berries of strain S64 was 35?-40?,and the optimum fermentation temperature of S64 was 37 ?. |
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