Study On Processing Technology And Quality Of Compound Yoghurt Including Nanguo Pear And Hawthorn

Nanguo Pear not only has unique flavor,but also has high nutritional value,which It has been known as"the king of pears"for many years.Hawthorn is a unique medicinal and edible homologous food in China.Hawthorn is rich in a variety of nutritional elements.The VC content of Hawthorn can reach 890 mg/kg,and it is known as the king of fruits due to its high pectin content.Hawthorn has high acidity and low sugar-to-acid ratio.When eaten directly,Hawthorn tastes sour and astringent,and the acceptability of the population is low.In most cases,it is mainly used for processing into hawthorn slices,hawthorn cakes,fruit peels,jams and other products,but deep-processed products are relatively monotonous.As a healthy and delicious drink,yogurt has a very broad market development prospect.Therefore this paper mainly analyzes the processing technology and quality of Compound Yoghurt including Nanguo Pear and Hawthorn.Firstly,taking Nanguo pear as the main raw material,the pre fermentation process of Nanguo pear was determined through orthogonal test.Secondly,the best production formula of Nanguo Pear Hawthorn compound yogurt was determined through the response surface test of three factors and three levels.The quality characteristics of the compound yogurt and the dynamic changes of the quality of the compound yogurt during storage were studied.The main results are as follows:1.Process optimization of Nanguo pear pre-fermentation treatment.Taking fermentation temperature,fermentation time,inoculation amount of two lactic acid bacteria（Lactobacillus casei and Bifidobacterium lactis）and inoculation ratio of two lactic acid bacteria as variables,combined with single factor and orthogonal experiment,the optimal fermentation process of Nanguo pear was determined.The optimum fermentation conditions were as follows:fermentation temperature 38℃,fermentation time 36 h,mixed inoculum of lactic acid bacteria 3%,and the inoculation ratio of two lactic acid bacteria（Lactobacillus casei:Bifidobacterium lactis）2:1.The total phenolic content in the fermentation product was 97.21 mg/100g,and the total flavonoid content was 36.24 mg/100g.2.The formula of Nanguo Pear Hawthorn compound yogurt was optimized.Taking the sensory score of Nanguo Li-Hawthorn compound yogurt as an index,combined with the results of single factor and response surface tests,the optimal formula of yogurt was determined.The formula is as follows:the addition of milk is76.10%,the addition of hawthorn pulp is 5.90%,the addition of Nanguo pear fermentation broth is 10.60%,and the addition of white sugar is 7.40%,and the final sensory score is 90 points.3.The quality of compound yogurt including Nanguo Pear and Hawthorn was analyzed.（1）The color of compound yoghurt including Nanguo Pear and Hawthorn is milky white.The compound yogurt full of strong yogurt aroma,fresh Hawthorn aroma and Nanguo Pear aroma.The tissue state is in good condition,there is no whey precipitation,and there is slight Hawthorn small particle precipitation.（2）The protein content of Nanguo Pear Hawthorn compound yogurt was 2.69 g/100g,the fat content was 3.03 g/100g,the moisture content was 82.39 g/100g,the pH value was4.49,the acidity was 80.33 ^oT,the water holding capacity was 79.48%,the total number of lactic acid bacteria was 8.64/log(CFU·m L^-1),and the coliform group was not detected.（3）Under different concentrations,the·OH,ABTS⁺and DPPH radical scavenging rates of Nanguo Pear Hawthorn compound yogurt increased with the increase of yogurt concentration.4.Dynamic change analysis of quality indexes of Nanguo pear and hawthorn compound yogurt during storage.Under the three temperature conditions of 4℃,25℃and 30℃,the sensory evaluation score,pH value and the total number of lactic acid bacteria decreased with the prolongation of storage time,while the acidity was the opposite.Under the condition of 4℃,the total acid of lactic acid bacteria was lower than 10~6CFU/m L on the 20th day,and at 25℃and 30℃,the total lactic acid bacteria was lower than 10~6CFU/m L on the 12th day and the 8th day,respectively,which was lower than the national standard.In conclusion,the Nanguo Pear and Hawthorn compound yogurt developed in this study has a soft taste,suitable flavor and good nutritional and health value.This research not only enriches the deep processing of Nanguo Pear and hawthorn,but also helps to promote the healthy and rapid development of Nanguo Pear and hawthorn industry in China.