| Lactobacillus plantarum exopolysaccharides(EPSs)are a class of macromolecular saccharides with unique physicochemical properties and physiological functions,which are secreted to the outside of the cell during the growth and metabolism of L.plantarum,and belong to the secondary metabolites of microorganisms..As a natural safe product,EPSs can improve food texture and can be added to food as a natural food quality improver.At the same time,L.plantarum EPSs have a variety of physiological activities,such as:lowering cholesterol,lowering blood sugar,regulating intestinal flora,regulating immunity,anti-oxidation,anti-tumor and so on.Fish gelatin is prepared from fish skin,bone,and phosphorus.It has the functions of thickening,stabilizing,and gelling.It also has various physiological functions such as treating ulcers and lowering blood pressure.Its quality is not easily affected by the glue source material.And can meet the needs of special populations(religious believers,etc.),so it is considered to be the most potential mammalian gelatin substitute.There are few reports on the synergistic improvement of the quality of low-fat yogurt by adding EPSs and fish gelatin to low-fat yogurt.In this study,the L.plantarum JLAU103 EPSs obtained in the previous stage were combined with fish gelatin and added to low-fat milk to prepare low-fat yogurt,and its synergistic effect on the quality of low-fat yogurt was studied.The main findings are as follows:1.Through the separation and extraction of L.plantarum JLAU103 EPSs,the obtained exopolysaccharide was mixed with fish gelatin in different proportions and added to low-fat yogurt to analyze its effect on the quality of low-fat yogurt.It was found that the addition of L.plantarum EPSs and fish gelatin increased the viscosity,water holding capacity,p H value and decreased titratable acidity of low-fat yogurt.Scanning electron microscope(SEM)observed that the microstructure of low-fat yoghurt with 0.10%EPSs and 0.60%fish gelatin had smaller protein network voids and more compact structure.Compared with the low-fat yogurt in the control group,the number of viable bacteria was significantly increased,reaching 8.40×108CFU/m L.The content of characteristic volatile flavor substances was significantly increased,such as diacetyl,2-nonanone,2,3-pentanedione,butyric acid,nonanoic acid,nonanal,etc.,which gave the yogurt a unique flavor and improved the sensory score.The results showed that the quality of low-fat yogurt could be improved to a certain extent by adding L.plantarum JLAU103 EPSs in combination with fish gelatin to low-fat yogurt.2.By analyzing the texture and rheological properties of low-fat yogurt,the results showed that the hardness,viscosity,cohesion and elasticity of low-fat yogurt with 0.60%fish gelatin and0.10%L.plantarum EPSs were significantly higher than those of normal yogurt and low-fat yogurt.improve.The elastic components were dominant in each group of yogurt samples,and all samples showed solid-like characteristics.The addition of L.plantarum EPSs reduced the thixotropic ring area of low-fat yogurt and enhanced the recovery and stability of low-fat yogurt.Increased total strain resulted in a firmer,firmer gel network for low-fat yogurt.The addition of L.plantarum EPSs and fish gelatin fat yogurt was found to have better flowability for apparent viscosity measurements.The above results show that the texture and rheological properties of low-fat yogurt can be improved to a certain extent by adding L.plantarum JLAU103 EPSs and fish gelatin to low-fat yogurt.3.The prepared low-fat yogurt supplemented with L.plantarum EPSs and fish gelatin was stored at 4°C for 21 days and at room temperature for 7 days,respectively,to study its quality changes during the storage period.During the storage period of 21 days at 4°C,the addition of L.plantarum EPSs synergistically with fish gelatin to low-fat yogurt inhibited the increase of titratable acidity and the decrease of p H of low-fat yogurt during storage,and maintained the viscosity of low-fat yogurt during storage.The change is stable,and the number of viable bacteria in the storage period is significantly increased,which is maintained above 1.25×10~8CFU,and the water holding capacity is significantly improved.During the 7-day storage period at room temperature,the addition of L.plantarum EPSs and fish gelatin to low-fat yogurt also inhibited the increase of titratable acidity and the decrease of p H of low-fat yogurt during storage,and maintained the viscosity of low-fat yogurt during storage.The change is stable,the water holding capacity is improved,and the viable bacteria number during the storage period is increased,which is maintained at more than 1.64×10~7 CFU/m L.The above results show that by combining L.plantarum JLAU103 EPSs with fish gelatin added to low-fat yogurt,can improve the quality of low-fat yogurt during the storage period to a certain extent. |
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