| The natural sweeteners erythritol,mogroside and steviol glycosides were mixed to prepare compound sugars,which were used as sweeteners to prepare sucrose-free yogurt.The system compares the sensory and physical and chemical properties of plain yogurt(containing sucrose)and sucrose-free yogurt fermented at 43°C and 37°C.A combination of sensory evaluation and electronic tongue detection is used to obtain a compound sugar formula that is as sweet as sucrose solution.Sensory evaluation using electronic nose,electronic tongue,electronic eye and evaluation group,the phenolphthalein indicator method,texture instrument,rheometer,plate counting method,calorimeter wae used to test acidity,hardness,viscosity and quantity of lactic acid bacteria during the fermentation of common yogurt and sugar-free yogurt with the same sweetness,respectively.The results are as follows.(1)Erythritol,mogroside and steviol glycosides were compounded according to99:2:2,and their sweetness was similar to that of sucrose;the sweetness intensity ratio of compound sweetener and sucrose were 7.77:1.Compared with sucrose,compound sweetener had a significant lower in calorific value under the same sweetness(p<0.05).(2)Fermentation at 43°C,during the fermentation process,the acid production rate of plain yogurt with the same sweetness and sucrose-free yogurt has a significant difference(p<0.05).Compared with the same sweetness,there was no significant difference in hardness and viscosity at the fermentation time of 1h-3h(p>0.05),after 4h,the hardness and viscosity of sucrose-free yogurt increased significantly(p<0.05);as the fermentation time progresses,the growth rate of the number of lactic acid bacteria in sucrose-free yogurt was greater than that of plain yogurt.At the end of the fermentation,the fermentation times for sucrose content of 4%,6%,8%,10%,and 12%were 6h,5h,7h,7h,7h,respectively;while the fermentation time of sucrose-free yogurt with the same sweetness was 5h.The range of fermentation acidity was 70.11?T-72.18?T,yogurt with sucrose content of 8%,10%,12%and sucrose-free yogurt with the same sweetness had significant differences in acidity(p<0.05),while sucrose content of 4%,6%there was no significant difference in acidity between yogurt and sucrose-free yogurt with the same sweetness(p>0.05).The sucrose content of 4%,6%,8%yogurthad no significant difference in hardness compared with the same sweetness sucrose-free yogurt(p>0.05),while the sucrose content of 10%and12%yogurt had significant differences in hardness compared with the same sweetness sucrose-free yogurt(p<0.05);there was no significant difference among different concentrations in viscosity(p>0.05).The sucrose content of 4%,10%,12%yogurt had significant differences in smell,taste and color with the same sweetness sucrose-free yogurt(p<0.05),compared with sucrose-free yogurt with the same sweetness,yogurt with sucrose concentration of has no significant difference while the sucrose content of 6%and 8%yogurt had no significant difference in smell,taste and color compared with the same sweetness sucrose-free yogurt(p>0.05).After ripening for 18h at 4?,the acidity of yogurt with sucrose content of 4%,6%,8%,and 10%was significantly higher than that of sucrose-free yogurt with the same sweetness(p<0.05);there is no significant difference in acidity between yogurt with 12%sucrose content and sucrose-free yogurt with the same sweetness(p>0.05).The hardness of sucrose-free yogurt with the same sweetness are higher than those of plain yogurt,but there is no significant difference(p>0.05),only the yogurt with a sucrose concentration of 4%and the sucrose-free yogurt with the same sweetness had a significant difference in viscosity(p<0.05).The same sweetness of yogurt had no significant difference in smell;there was a significant difference in taste;in terms of color,only yogurt with sucrose content of 8%and 10%had a significant difference compared with the same sweetness sucrose-free yogurt(p<0.05),and there was no significant difference in other concentrations(p>0.05).The number of viable lactic acid bacteria in yogurt with sucrose content of 6%,8%and 10%was significantly lower than that of sucrose-free yogurt(p<0.05);there was no significant difference in other concentrations(p>0.05).(3)Fermentation at 37°C,during the fermentation process,There was a significant difference in acid production rate between plain yogurt and non-sucrose yogurt with equal sweetness(p<0.05).After fermentated for 5h,yogurt with a sucrose concentration of 4%,the hardness and viscosity were significantly different from those of sucrose-free yogurt with the same sweetness(p<0.05);after 4h of fermentation,yogurt with sucrose content of 6%and 8%and those with the same sweetness,there were significant differences in hardness and viscosity(p<0.05);after 4h of fermentation,yogurt with sucrose content of 10%and 12%and sucrose-free yogurt with the same sweetness had significant differences in hardness and viscosity(p<0.05).As the fermentation time progresses,the growth rate of the number of lactic acid bacteria in sucrose-free yogurt was greater than that of ordinary yogurt.At the end of the fermentation,the fermentation time for sucrose content of 4%,6%,8%,10%,and 12%was 7h,7h,7h,9h,9h,respectively;while the fermentation time of sucrose-free yogurt with the same sweetness was 6h,5h,respectively;5h,7h,7h;the range of fermentation acidity was 70.01?T-73.4?T,yogurt with sucrose content of 4%,6%,10%,12%and sucrose-free yogurt with the same sweetness had significant differences in acidity(p<0.05),there was no significant difference in acidity between yogurt with sucrose content of 8%and sucrose-free yogurt with the same sweetness(p>0.05).The yogurt with sucrose content of 4%and 12%had significant differences in hardness compared with the same sweetness yogurt(p<0.05),while the yogurt with sucrose content of 6%,8%and 10%had no significant differences in hardness compared with the same sweetness yogurt(p<0.05);there was no significant difference in viscosity between equal sweetness yogurt(p>0.05).The yogurt with sucrose content of 4%and the sucrose-free yogurt with the same sweetness had significant differences in smell,taste and color(p<0.05).Compared two yogurts at the same sweetness,the concentration of 6%only had significant differences in smell and taste(p>0.05),but no significant difference in color(p>0.05),compared with sucrose-free yogurt with the same sweetness;yogurt with 8%,10%,and 12%sucrose contents had significant differences in taste and color(p<0.05),but there was no significant difference in smell(p>0.05).After ripening for 18h at 4?,the acidity of yogurt with sucrose content of 6%,8%,and 12%were significantly higher than that of sucrose-free yogurt with the same sweetness(p<0.05);while yogurt with sucrose content of 4%and 10%compared with sucrose-free yogurt with the same sweetness,there was no significant difference in acidity(p>0.05).Under the same sweetness,the hardness of sucrose-free yogurt was larger than that of plain yogurt,but there was no significant difference(p>0.05).Only the yogurt with a sucrose concentration of 6%and the sucrose-free yogurt with the same sweetness have a significant difference in viscosity(p<0.05).The two yogurts at the same sweetness had no significant difference in smell and color(p>0.05),but significant differences in taste(p<0.05).There was significant differences in the number of lactic acid bacteria between yogurt with sucrose content of 4%,10%,and 12%and sucrose-free yogurt with the same sweetness(p<0.05),however,there was no significant difference in the number of lactic acid bacteria between yogurt with sucrose content of 6%,8%and sucrose-free yogurt with the same sweetness(p>0.05).Therefore,there were significant differences between sucrose-free yogurt fermented at the same temperature and sucrose-containing yogurt;there were also significant differences between yogurt fermented at different temperatures.The significant degree of the difference is related to the concentration of added sucrose or compound sugar. |
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