Preparation process for optimizing jam based on response surface method

Abstract

The invention relates to the technical field of jam preparation, and discloses a jam preparation process based on response surface method.The jam preparation process comprises the steps of raw material selection, raw material cleaning, pretreatment, color protection, softening and pulping, juice boiling and concentration, blending, canning, sterilization and cooling and the like. Wherein the raw materials of the jam are added according to analysis results of a single factor experiment and a response surface experiment. According to the preparation method disclosed by the invention, three natural products including tussilago farfara, apples and strawberries are taken as raw materials, a novel compound jam is developed, and optimal process conditions for preparing the jam are screened by combining a single-factor experiment and a response surface test; the in-vitro oxidation resistance of the jam is evaluated by measuring the DPPH clearance rate. The sensory score of the tussilago farfara-apple-strawberry compound jam prepared by the preparation method disclosed by the invention can be up to 96.3. The jam has relatively strong antioxidant activity, and the produced jam is light red, palatable in sourness and sweetness and free of peculiar smell; the sauce body is uniform and consistent, and a certain theoretical basis is provided for development of future products.

Description

Technical Field

[0001] The invention relates to the technical field of jam preparation, and in particular to a jam preparation process optimized based on response surface methodology. Background Art

[0002] Fruit is not only an integral part of human diet, but also an irreplaceable source of nutrients. Fresh fruits are prone to spoilage if not stored properly, which may lead to the loss of nutrients. Making jam from fresh fruits is an important and practical way to preserve fruits. This method can preserve the taste of fruits and ensure that the nutrients of fruits are not lost. At present, single jams account for a large proportion of the market, and compound jam products with antioxidant functions are relatively rare. Tussilago farfara L. is a perennial herb belonging to the Asteraceae family. In traditional Chinese medicine, it is mainly used to treat respiratory diseases, and the flower buds are preferred as medicine. Studies have shown that the content of flavonoids in Tussilago farfara L. is high. In recent years, relevant research on flavonoids in Tussilago farfara L. has shown a gradual increase, but most of them remain at the theoretical level. Tussilago farfara L. and apple are both traditional Chinese medicinal materials with medicinal and edible properties, and have high medicinal value. Therefore, they can be used as cash crops to bring certain economic benefits to the planting areas. Apple (Malus pumila Mill.) belongs to the Rosaceae family, including phenolic substances, dietary fiber, pectin and vitamins. It is rich in nutrients, including phenolic substances, including flavonols, hydroxycinnamic acid, flavan-3-ol, dihydrochalcone and anthocyanidin. Phenolic compounds, as secondary metabolites of plants, have a wide range of biological activities, such as antioxidant activity, anti-tumor and anti-inflammatory effects, cardiovascular disease prevention and weight control. Strawberries have the effects of nourishing yin and blood, lowering blood pressure and anti-aging.

[0003] Therefore, it is urgent for those skilled in the art to provide a preparation process of jam with antioxidant function based on response surface methodology to provide a certain theoretical basis for future product development. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a preparation process for optimizing jam based on response surface methodology, thereby solving the problem of lack of antioxidant function of compound jam in the prior art.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a preparation process for jam optimized based on response surface methodology, which specifically comprises the following steps:

[0007] S1: Select raw materials: select apples and strawberries with bright colors and no damage, rot, disease or insects, and select coltsfoot flowers;

[0008] S2: Cleaning materials: Use ultrapure water to clean the surface of apples and strawberries;

[0009] S3: Pretreatment: After the washing step, remove the apple core, remove the strawberry stalk, and extract the total flavonoids extract of coltsfoot;

[0010] S4: Color protection: Take two 1000mL large beakers, put apples and strawberries into different beakers and add 0.6% citric acid solution for soaking;

[0011] S5: Softening and beating: Soften the apples and strawberries separately, keep the pulp after softening, discard the water during softening, add the pulp into a wall breaking machine and beat into pulp;

[0012] S6: Boiling and concentrating the juice: Boil the beaten jam, add citric acid, white sugar, CMC-Na and vitamin C during the boiling process to adjust the sweetness and viscosity, and then concentrate and serve;

[0013] S7: Preparation: mixing apple pulp, strawberry pulp and coltsfoot total flavonoids extract according to proportion;

[0014] S8: Canning: sterilize in a water bath and can while hot;

[0015] S9: Sterilization and cooling: Put the canned jam into the sterilizer for sterilization, and cool it by segmented cooling after the sterilization;

[0016] Among them, the amount of white sugar added, the amount of citric acid added, the amount of CMC-Na added and the amount of vitamin C added in step S6 and the compound proportion of jam in step S7 are all added according to the analysis results of the single factor experiment and the response surface experiment.

[0017] Furthermore, in step S3, the strawberry is cut into four petals in equal parts, and the method for extracting the coltsfoot total flavonoids extract is as follows: the coltsfoot is placed in an oven for drying at 50° C., and then ground into powder by a powder grinder for extraction.

[0018] Furthermore, the specific softening step of the softening and pulping in step S5 is to put the apples and strawberries into pots of the same texture respectively, add a proper amount of water into the pots, and heat until the flesh expands and softens.

[0019] Furthermore, the cooking temperature of the fruit pulp in step S6 is 120° C., and the standard for taking the fruit out of the pot is that the jam falls in the form of slices when picked up with a flat spoon.

[0020] Furthermore, the sterilization condition in step S9 is sterilization at 112° C. for 5 minutes.

[0021] Furthermore, the single factor experiment specifically uses sensory scores as the evaluation index, and on the basis of keeping other factors and levels unchanged, the addition amount of the compound jam is determined according to the influence of the apple pulp addition ratio, strawberry pulp addition ratio, white sugar addition amount, vitamin C addition amount, citric acid addition amount and CMC-Na addition amount on the sensory score of the compound jam.

[0022] Furthermore, the response surface experiment is based on the single factor experiment, with the sensory score of coltsfoot-apple-strawberry composite jam as the response value (Z), the amount of white sugar added (A), the amount of vitamin C (B), the amount of citric acid added (C) and the amount of CMC-Na added (D) as the experimental factors, and the Design Expert8.0.6 software is used to design a 4-factor 3-level Box-Behnken response surface experiment, and the composite proportion of the fruit pulp and the amount of white sugar added, the amount of vitamin C added, the amount of citric acid added, and the amount of CMC-Na added are determined.

[0023] Furthermore, the optimal regression equation of the response surface experiment is:

[0024] Z=91.98+5.85A-0.26B-0.46C-2.57D+2.78AB+0.13AC+2.1AD+0.75BC+0.5BD+1.9CD-10.46A 2 +0.031B 2 -0.59C 2 -0.46D 2 , where Z is the sensory score response value of coltsfoot-apple-strawberry composite jam, A is the amount of white sugar added, B is the amount of vitamin C, C is the amount of citric acid added, and D is the amount of CMC-Na added.

[0025] Furthermore, the ratio of apple puree to strawberry puree is 6:4, the amount of added white sugar is 50%, the amount of added vitamin C is 0.07%, the amount of added citric acid is 1.0%, and the amount of added CMC-Na is 0.61%, and the total flavonoids content of coltsfoot flower is 7.8 mg / 100 g.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The preparation method of the present invention uses three natural products, namely coltsfoot, apple and strawberry, as raw materials to develop a new type of composite jam. The method of the present invention combines single factor experiment and response surface test to screen out the optimal process conditions for jam preparation; the in vitro antioxidant capacity of the jam is evaluated by measuring the DPPH clearance rate. The sensory score of the coltsfoot-apple-strawberry composite jam prepared by the preparation method of the present invention can reach up to 96.3 points. And it has relatively strong antioxidant activity, the produced jam is light red, sweet and sour, and has no peculiar smell; the jam is uniform and consistent, which provides a certain theoretical basis for the development of future products. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Attached Figure 1 The process flow chart of jam preparation in this embodiment;

[0029] Attached Figure 2 This is a sensory scoring diagram of different ratios of apple puree to strawberry puree in this embodiment;

[0030] Attached Figure 3 This is a graph showing the effect of the amount of white sugar added on the sensory score of coltsfoot-apple-strawberry composite jam in this embodiment;

[0031] Attached Figure 4 This is a graph showing the effect of the amount of vitamin C added on the sensory score of coltsfoot-apple-strawberry composite jam in this embodiment;

[0032] Attached Figure 5 This is a graph showing the effect of the amount of citric acid added on the sensory score of coltsfoot-apple-strawberry composite jam in this example;

[0033] Attached Figure 6 This is a graph showing the effect of the amount of CMC-Na added on the sensory score of coltsfoot-apple-strawberry composite jam in this embodiment;

[0034] Attached Figure 7 This is a response diagram showing the effect of the amount of white sugar added and the amount of CMC-Na added on the sensory score of coltsfoot-apple-strawberry composite jam in this embodiment;

[0035] Attached Figure 8 This is a response diagram showing the effect of the amount of added white sugar and the amount of added citric acid on the sensory score of coltsfoot-apple-strawberry composite jam in this embodiment;

[0036] Attached Fig. 9 This is a response diagram showing the effect of the amount of white sugar added and the amount of vitamin C added on the sensory score of coltsfoot-apple-strawberry composite jam in this embodiment;

[0037] Attached Fig.10 This is a response diagram showing the effect of the amount of CMC-Na added and the amount of vitamin C added on the sensory score of coltsfoot-apple-strawberry composite jam in this embodiment;

[0038] Attached Fig.11 This is a response diagram showing the effect of the amount of CMC-Na added and the amount of citric acid added on the sensory score of coltsfoot-apple-strawberry composite jam in this embodiment;

[0039] Attached Fig.12 This is a response diagram showing the effect of the amount of vitamin C added and the amount of citric acid added on the sensory score of coltsfoot-apple-strawberry composite jam in this embodiment;

[0040] Attached Fig.13 The best process diagram for optimizing the response surface model in this embodiment;

[0041] Attached Fig.14 Graph showing the scavenging ability of total flavonoids on DPPH free radicals in this example. DETAILED DESCRIPTION

[0042] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0043] The sources of materials, reagents and instruments selected in this example are as follows:

[0044] Coltsfoot, sourced from Anhui Xintai Pharmaceutical Co., Ltd., identified by the Pharmacy Department of Xi'an Third Hospital, Affiliated Hospital of Northwest University; apples, produced in Luochuan; strawberries, produced in Dandong, China; sodium citrate, white sugar, sodium nitrite, and vitamin C food additives are all food grade. Anhydrous ethanol, aluminum nitrate, and sodium hydroxide (Fuchen Tianjin Chemical Reagent Co., Ltd.); rutin reference substance (purity > 98%, Ruji Biotechnology Development Co., Ltd.); 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH, Ruji Biotechnology Development Co., Ltd., all reagents are analytical grade). UV-mini1258 UV-visible spectrophotometer (Shimadzu Corporation, Japan); SB25-12DTD ultrasonic cleaning machine (Ningbo Xinzhi); high-speed refrigerated centrifuge (Beckman Coulter, USA); water bath, juicer\beater (Meiling)

[0045] Example 1

[0046] See attached Figure 1 In this embodiment, a preparation process of jam is optimized based on response surface methodology, which specifically includes the following steps:

[0047] S1: Select raw materials: select apples and strawberries with bright colors and no damage, rot, disease or insects, and select coltsfoot flowers;

[0048] S2: Cleaning materials: Use ultrapure water to clean the surface of apples and strawberries;

[0049] S3: Pretreatment: After the washing step, remove the apple core, remove the strawberry stalk, and cut the strawberry into four petals. Dry the coltsfoot flowers in an oven at 50°C, grind them into powder using a powder grinder, and then extract the coltsfoot flower total flavonoids extract;

[0050] S4: Color protection: Take two 1000mL large beakers, put apples and strawberries into different beakers and add 0.6% citric acid solution for soaking;

[0051] S5: Softening and pulping: Put apples and strawberries into pots of the same texture, add appropriate amount of water to the pots, heat until the flesh expands and softens, keep the flesh after softening, discard the water during softening, add the flesh into a wall breaking machine and beat into pulp;

[0052] S6: Boiling and concentrating the juice: Boil the beaten jam at a temperature of 120°C, add citric acid, white sugar, CMC-Na and vitamin C during the boiling process to adjust the acidity and treat the sugar respectively, and remove from the pot after concentration. The standard for removing from the pot is that the jam falls in flakes when picked up with a flat spoon;

[0053] S7: Preparation: mix apple pulp, strawberry pulp, coltsfoot total flavonoids extract, white sugar and citric acid according to proportion;

[0054] S8: Canning: sterilize in a water bath and can while hot;

[0055] S9: Sterilization and cooling: Put the canned jam into the autoclave for sterilization. The sterilization condition is to sterilize at 112°C for 5 minutes. After the sterilization, cool it by segmented cooling method.

[0056] Among them, the amount of white sugar added in step S6, the amount of vitamin C added, the amount of citric acid added, the amount of CMC-Na added, and the compound proportion of jam in step S7 are all added according to the analysis results of the single factor experiment and the response surface experiment.

[0057] The single-factor experiment specifically uses sensory scores as the evaluation index. On the basis of keeping other factors and levels unchanged, the addition amount of apple pulp, strawberry pulp, white sugar, vitamin C, citric acid and CMC-Na is determined according to their effects on the sensory scores of compound jam.

[0058] The response surface experiment was based on the single factor experiment. The sensory score of coltsfoot-apple-strawberry composite jam was taken as the response value (Z), and the amount of white sugar added (A), vitamin C added (B), citric acid added (C) and CMC-Na added (D) were taken as the experimental factors. The Design Expert8.0.6 software was used to design a 4-factor 3-level Box-Behnken response surface experiment, and the composite proportion of the fruit paste and the amount of white sugar added, vitamin C added, citric acid added and CMC-Na added were determined.

[0059] Example 2

[0060] According to the ratio of apple pulp to strawberry pulp of 5:5, 6:4, 7:3, 8:2 and 10:1, 50g of apple pulp and 50, 20, 15, 10 and 5g of strawberry pulp were taken respectively. The amount of white sugar added was 40%, the amount of citric acid added was 0.15%, and the amount of sodium carboxymethyl cellulose added was 0.5% to prepare apple-strawberry composite jam. Combined with sensory evaluation and texture (viscosity value, acidity value) determination, the optimal ratio of apple to strawberry in the jam was finally determined.

[0061] The sensory scores of different apple puree and strawberry puree ratios are shown in the attached Figure 2 , by the attached Figure 2 It can be seen that when the ratio of apple pulp to strawberry pulp is 6:4, the sensory score reaches 84 points, which is the highest value. At this time, the apple and strawberry fruit aromas are relatively strong, and the sweetness of the pulp is moderate. When the apple pulp ratio is greater than 6:4, the strawberry fruit aroma will be light and the taste will be sour; when the apple pulp ratio is less than 6:4, the apple fruit aroma will be light and the taste will be too sweet. Therefore, the ratio of apple pulp to strawberry pulp is determined and selected as 6:4, because the jam ratio is relatively important, and on this basis, the process optimization of preparing compound jam is completed.

[0062] Example 3

[0063] Taking sensory score as the inspection index, the effects of white sugar addition, vitamin C addition, citric acid addition and CMC-Na addition on the sensory score of compound jam were studied respectively on the basis of keeping other factors and levels unchanged. The levels of each factor were designed as follows: white sugar addition of 30%, 35%, 40%, 45%, 50% and 55%; vitamin C addition of 0.05%, 0.10%, 0.20%, 0.30%, 0.50% and 0.60%; citric acid addition of 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0% and 3.5%; CMC-Na addition of 0.33%, 0.46%, 0.60%, 0.70% and 0.80%.

[0064] The effect of sugar addition on sensory scores of coltsfoot-apple-strawberry compound jam is shown in the attached Figure 3 , by the attached Figure 3 It can be seen that when the amount of white sugar added is 52%, the sensory score is the highest (86 points), and the taste is moderately sweet and sour, moderately viscous, and the gel is stable. When the amount of white sugar added is less than 45%, the sauce is basically gelled, but its stability is relatively poor, the viscosity is small, and it is acidic; when the amount of white sugar added is greater than 55%, the sauce gels well and has relatively good stability, but it is relatively viscous, the taste is sweet or too sweet, and the fruity aroma is also partially covered by the sweetness. Therefore, the amount of white sugar added is selected to be 52%.

[0065] Effect of vitamin C addition on sensory scores of coltsfoot-apple-strawberry compound jam Figure 4 , by the attached Figure 4 It can be seen that when the amount of vitamin C added is between 0.05% and 0.15%, the sensory score of the composite jam increases with the increase of the amount of vitamin C added, and the highest sensory score is achieved when the amount is increased to 0.15%. Within this range, the addition of vitamin C helps to maintain its orange-red color and effectively alleviates the sweetness of the jam. At this time, the jam has good gelling properties and moderate sourness and sweetness. When the amount of vitamin C added exceeds 0.15%, the stability of the jam decreases, and the taste obviously has an unpleasant feeling of being too sour. Therefore, the amount of vitamin C added is selected to be 0.15%.

[0066] The effect of citric acid addition on sensory evaluation of coltsfoot-apple-strawberry composite jam is shown in the attached Figure 5 , by the attached Figure 5 It can be seen that when the amount of citric acid added is 2.5%, the jam tastes mild; as the amount of citric acid added increases, the jam tastes sour, the viscosity of the jam decreases, and the color becomes darker. Therefore, the amount of citric acid added is selected to be 2.5%.

[0067] The effect of CMC-Na addition on the sensory score of coltsfoot-apple-strawberry composite jam is shown in the attached Figure 6 , by the attached Figure 6 It can be seen that when the addition amount of CMC-Na is within the range of 0.35% to 0.75%, as the addition amount of CMC-Na increases, the sensory score of the composite jam shows an upward trend; when it increases to 0.75%, the stability of the sauce gel tends to be good and non-viscous, and the comprehensive sensory score is the highest (89 points). When it is greater than 0.75%, the sauce gel is viscous and difficult to spread. Therefore, the addition amount of CMC-Na is selected to be 0.75%. Example 4

[0068] Accurately weigh 0.0171g of rutin standard and dissolve it in 50% ethanol and dilute it to a 50mL volumetric flask to prepare a 0.342mg / mL rutin standard solution. Draw a rutin standard curve. Perform linear regression with the absorbance value Y and the rutin standard concentration C (g / mL). After completing the above steps, accurately measure 1000uL of total flavonoids extract and dilute it to a 50mL volumetric flask. Use formula (1) to calculate the extraction rate of total flavonoids in coltsfoot flower.

[0069]

[0070] Where: C: is the total flavonoids mass concentration of the sample coltsfoot flower extract (mg / mL);

[0071] N: dilution multiple;

[0072] V: volume of sample extract (mL);

[0073] M: sample mass (m).

[0074] Accurately weigh 10 mg DPPH in a 250 mL volumetric flask, dissolve it in anhydrous ethanol as a solvent and set to volume for later use. Accurately measure 0.084 mg / mL of total flavonoids from coltsfoot and 0.005 g of vitamin C, and dilute the total flavonoids extract from coltsfoot and vitamin C of equal concentration to 0.005 mg / mL, 0.010 mg / mL, 0.020 mg / mL, 0.040 mg / mL and 0.080 mg / mL, take 2 mL of different concentrations of total flavonoids extract from coltsfoot and equal concentrations of vitamin C dilutions in test tubes, add 2 mL of the prepared DPPH solution, mix evenly, react for 30 minutes, and measure the absorbance (Ai) at a wavelength of 517 nm; replace the absorbance (Aj) of 2 mL of DPPH with 2 mL of anhydrous ethanol; replace the absorbance (A0) of 2 mL of the test solution with 2 mL of anhydrous ethanol. Calculate the DPPH free radical scavenging rate (Y) as shown in formula (2).

[0075]

[0076] According to the above method, the regression equation is: Y = 4.513X + 0.001; R 2 =0.9995, and the total flavonoids concentration in the sample was calculated according to the rutin standard curve. Through calculation, it can be known that the total flavonoids content of honey-made coltsfoot in jam is 7.8 mg / 100 g.

[0077] See attached Fig.14, the scavenging rate of total flavonoids and L-ascorbic acid on DPPH free radicals in the mass concentration range of 0.005 to 0.06 mg / mL increased with the increase of working solution concentration. When the concentration increased to 0.08 mg / mL, the scavenging rate of vitamin C on DPPH free radicals reached 97.1%, and the scavenging rate of total flavonoids on DPPH free radicals reached 85%. The experimental results show that the antioxidant capacity of total flavonoids in coltsfoot flower is similar to that of L-ascorbic acid. By measuring the scavenging capacity of total flavonoids in coltsfoot flower on DPPH free radicals, it is determined that its in vitro antioxidant activity is strong.

[0078] Example 5

[0079] On the basis of the single factor experiment, the sensory score of coltsfoot-apple-strawberry compound jam was used as the response value (Y), and the amount of white sugar added (A), vitamin C amount (B), citric acid added (C) and CMC-Na added (D) were used as experimental factors. The Design Expert 8.0.6 software was used to design a 4-factor 3-level Box-Behnken response surface experiment, and the results were analyzed. The factor level design is shown in Table 1.

[0080] Table 1. Response surface experimental factors and levels

[0081]

[0082] The Box-Behnken Design response surface test design scheme and results are shown in Table 2, and the ANOVA analysis of variance of the binomial model is shown in Table 3. Through the Box-Behnken response surface test design results, the optimal preparation process with the highest sensory score was obtained.

[0083] Table 2 Box-Behnken response surface experimental design and results

[0084]

[0085] Table 4 ANOVA analysis of variance for the binomial model

[0086]

[0087]

[0088] Among them: *** is extremely significant (p < 0.001), ** is relatively significant (p < 0.01), * is significant (p < 0.05)

[0089] Using Design Expert 8.0.6 software, multivariate analysis was performed with A-white sugar addition (%), B-CMC-Na addition (%), C-vitamin C (%) and D-citric acid addition (%) as variables and sensory evaluation as the response value, and the quadratic regression equation was obtained: sensory score Z = 91.98 + 5.85A-0.26B-0.46C-2.57D+2.78AB+0.13AC+2.1AD+0.75BC+0.5BD+1.9CD-10.46A 2 +0.031B 2 -0.59C 2 -0.46D 2 The binomial model ANOVA analysis was performed, and the results are shown in Table 3. It can be seen that the regression model P<0.001 is extremely significant, and the P value of the lack of fit term is 0.8849, which is extremely insignificant. The data show that the influence of the quadratic terms AB and AD on the sensory score is significant (P<0.05), and A 2 (P<0.001) showed an extremely significant level, and AC, BC and BD had no significant effect. At the same time, according to the regression variance analysis in the table, different factors have different effects on sensory scores, among which the addition amount of the four factors has different effects: white sugar> citric acid> vitamin C> CMC-Na. At the same time, the model determination coefficient R 2 =0.9713 This data indicates a good fit, and the corrected determination coefficient is Adj R-Squared = 0.9427, which confirms that the predicted value and the actual value are highly consistent, so this regression model is suitable for the effective optimization of the compound jam preparation process. In summary, it shows that the regression model is effective and can be used as a feasible method to optimize the compound jam preparation process.

[0090] Example 6

[0091] See attached Figure 7 -Attached Fig.12 , which is the response surface diagram of the pairwise interactions between various factors of coltsfoot-apple-strawberry compound jam additives. In the response surface diagram, if the curve tends to be steeper, it indicates that the interaction between the two is more significant, and vice versa. Figure 7-12 As can be seen from the figure, the response surface plot is relatively flat, indicating that the interactions among BC, BD, AC, and CD are not significant. Figures 7 and 8 It can be seen that the response surface plot is steep, indicating that the interaction between factors AB and AD is significant, which is consistent with the results of ANOVA.

[0092] Through response surface analysis, see Appendix Fig.13 , while keeping the addition amount of other components unchanged, the optimal preparation process is as follows Fig.13As shown in the figure, the response surface test results show that the best preparation process formula is 50% white sugar, 0.07% vitamin C, 1.0% citric acid and 0.61% CMC-Na. Under the optimized conditions, the score of the sensory comprehensive scoring standard and the model prediction value are 96.3 points. By repeating this process flow, the comprehensive score under this condition is 96.27 points, which is close to the model prediction value. The experimental results suggest that the response surface optimization regression model has a certain guiding significance for the actual process operation.

[0093] Several testers of different genders and ages were selected for the test. The sensory evaluation of the coltsfoot flower-apple-strawberry compound jam made with the above ratio was evaluated from five aspects: texture state, taste, aroma, color, and spreadability. The specific sensory scoring standards are shown in Table 5.

[0094] Table 5 Sensory evaluation standard scoring table

[0095]

[0096]

[0097] In summary, the composite ratio of apple pulp and strawberry pulp in the coltsfoot-apple-strawberry composite jam is 6:4, the added amount of white granulated sugar is 50%, the added amount of vitamin C is 0.07%, the added amount of citric acid is 1.0% and the added amount of CMC-Na is 0.61%. The prepared jam has good colloid stability, and the content of total flavonoids of effective antioxidant ingredients is 7.8 mg / 100 g. According to the antioxidant experiment of total flavonoids of coltsfoot, its scavenging rate of DPPH free radicals reaches 85%, so it is inferred that it has certain antioxidant activity; the jam has the highest sensory score under this optimized formula condition, and the jam produced according to the optimized process and formula is light red in color, naturally transparent; it has a delicate taste and is sweet and sour; it has a strong aroma of apples and strawberries and no peculiar smell; the jam is uniform and soft and gelatinous, has good fluidity, no sugar crystals, and good spreadability; there is no juice precipitation and no impurities.

[0098] The preparation method of this embodiment uses three natural products, namely coltsfoot, apple and strawberry, as raw materials to develop a new type of composite jam, explores the effects of the addition of three natural products and citric acid, white sugar, CMC-Na and vitamin C on the composite jam, and the method of this embodiment combines single factor experiment with response surface experiment to screen out the optimal process conditions for jam preparation; the in vitro antioxidant capacity of the jam is evaluated by measuring the DPPH clearance rate. The sensory score of the coltsfoot-apple-strawberry composite jam prepared by the preparation method of the present invention can reach up to 96.3 points. And it has relatively strong antioxidant activity, the jam produced is light red, sweet and sour, and has no peculiar smell; the sauce is uniform and consistent, which provides a certain theoretical basis for the development of future products.

[0099] The above is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solutions formed by the specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation process for jam optimized based on response surface methodology, characterized in that: The specific steps include: S1: Select raw materials: select apples and strawberries with bright colors and no damage, rot, disease or insects, and select coltsfoot flowers; S2: Cleaning materials: Use ultrapure water to clean the surface of apples and strawberries; S3: Pretreatment: remove the apple core, remove the strawberry stalk, and extract the total flavonoids extract of coltsfoot; S4: Color protection: Place apples and strawberries in different beakers and soak them in 0.6% citric acid solution; S5: Softening and beating: Soften the apples and strawberries separately, keep the pulp after softening, discard the water during softening, add the pulp into a wall breaking machine and beat into pulp; S6: Boiling and concentrating the juice: Boil the beaten jam, add citric acid, white sugar, CMC-Na and vitamin C during the boiling process to adjust the sweetness and viscosity, and then concentrate and serve; S7: Preparation: mixing apple pulp, strawberry pulp and coltsfoot total flavonoids extract according to proportion; S8: Canning: sterilize in a water bath and can while hot; S9: Sterilization and cooling: Put the canned jam into the sterilizer for sterilization, and cool it by segmented cooling after the sterilization; Among them, the amount of white sugar added, the amount of citric acid added, the amount of CMC-Na added and the amount of vitamin C added in step S6 and the compound proportion of jam in step S7 are all added according to the analysis results of the single factor experiment and the response surface experiment.

2. The preparation process of jam optimized based on response surface methodology according to claim 1, characterized in that: In the step S3, the strawberry is cut into four petals in equal parts. The method for extracting the coltsfoot total flavonoids extract is as follows: the coltsfoot is placed in an oven to dry at 50° C., and then ground into powder by a powder grinder for extraction.

3. The preparation process of jam optimized based on response surface methodology according to claim 1, characterized in that: The specific softening step of the softening and beating in step S5 is to put the apples and strawberries into pots with the same texture respectively, add a proper amount of water into the pots, and heat until the flesh expands and softens.

4. The preparation process of jam optimized based on response surface methodology according to claim 1, characterized in that: The cooking temperature of the fruit pulp in step S6 is 120° C., and the standard for taking the fruit out of the pot is that the fruit pulp falls in the form of slices when picked up with a flat spoon.

5. The preparation process of jam optimized based on response surface methodology according to claim 1, characterized in that: The sterilization condition in step S9 is sterilization at 112° C. for 5 minutes.

6. The preparation process of jam optimized based on response surface methodology according to claim 1, characterized in that: The single factor experiment specifically uses sensory scores as the evaluation index. On the basis of keeping other factors and levels unchanged, the addition amount of apple pulp, strawberry pulp, white sugar, vitamin C, citric acid and CMC-Na is determined according to their effects on the sensory scores of the compound jam.

7. The preparation process of jam optimized based on response surface methodology according to claim 6, characterized in that: The response surface experiment is based on the single factor experiment, with the sensory score of coltsfoot-apple-strawberry composite jam as the response value, the amount of white sugar added, the amount of vitamin C added, the amount of citric acid added and the amount of CMC-Na added as the experimental factors, and the DesignExpert8.0.6 software is used to design a 4-factor 3-level Box-Behnken response surface experiment, and the composite proportion of the fruit pulp and the amount of white sugar added, the amount of vitamin C added, the amount of citric acid added and the amount of CMC-Na added are determined.

8. The preparation process of jam optimized based on response surface methodology according to claim 7, characterized in that: The optimal regression equation of the response surface experiment is: Z=91.98+5.85A-0.26B-0.46C-2.57D+2.78AB+0.13AC+2.1AD+0.75BC+0.5BD+1.9CD-10.46A 2 +0.031B 2 -0.59C 2 -0.46D 2 , where Z is the sensory score response value of coltsfoot-apple-strawberry composite jam, A is the amount of white sugar added, B is the amount of vitamin C, C is the amount of citric acid added, and D is the amount of CMC-Na added.

9. The preparation process of jam optimized based on response surface methodology according to claim 8, characterized in that: The ratio of apple puree to strawberry puree is 6:4, the added amount of white sugar is 50%, the added amount of vitamin C is 0.07%, the added amount of citric acid is 1.0%, and the added amount of CMC-Na is 0.61%, and the total flavonoids content of coltsfoot flower is 7.8 mg / 100 g.

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