Prediction, identification, regulation and control or delay method for sugar flowing and sand returning phenomena of preserved strawberries

Abstract

The invention provides a method for predicting, identifying, regulating or delaying sugar flowing and sand returning phenomena of preserved strawberries, and relates to the field of agricultural product processing. The regulation and control method for the sugar flowing and sand returning phenomena of the preserved strawberries comprises the following steps: the preserved strawberries are prepared by soaking the preserved strawberries in cane sugar; the sugar flowing and sand returning phenomena of the preserved strawberries are regulated and controlled by controlling the maturity grade of the raw materials for making the preserved strawberries or whether trehalose is added or not during soaking; the raw materials for preparing the preserved strawberries are low in maturity grade, the prepared preserved strawberries are easy to return sand, the raw materials for preparing the preserved strawberries are high in maturity grade, and the prepared preserved strawberries are easy to flow sugar, so that the sand return can be delayed by improving the maturity grade of the strawberry raw materials, and the sugar flow can be delayed by reducing the maturity grade of the strawberry raw materials or adding trehalose. According to the method, the sugar flowing and sand returning phenomenon in the preparation process of the preserved strawberries can be regulated and controlled, and the sugar flowing or sand returning phenomenon is effectively delayed.

Description

Technical Field

[0001] The invention belongs to the field of agricultural product processing, and particularly relates to a method for predicting, identifying, regulating or delaying the phenomenon of sugar flow and sand return in strawberry dried fruit. Background Art

[0002] Preserved strawberries that have been dehydrated by sugaring and drying can have a soft and sticky texture, sweet flavor and rich taste. However, due to differences in raw materials, processes and storage time, there may be varying degrees of sugar flow or sand return, making the surface sticky or dry and granular substances precipitated, affecting the appearance and taste of the product.

[0003] Sugar flow and sanding are common phenomena in various candied fruits, dried fruits and even candy products. Sanding refers to the crystallization of amorphous sugar in sugar products, which makes the product lose its luster and changes its taste. Sugar flow is the reverse phenomenon of sanding, which is the phenomenon of moisture absorption in high temperature or high humidity environment, and appears as a high viscosity sugar liquid on the surface of food.

[0004] The currently known viewpoint attributes the occurrence of these phenomena in candied fruit candies to the content of invert sugar in the product, because sucrose is the most commonly used sugar, which can be converted into fructose and glucose in an acidic environment. Fructose has a stronger hygroscopicity than sucrose, and controlling the degree of sucrose conversion during the candiing process becomes the key to controlling the product's sand return or sugar flow phenomenon. It is generally believed that when the water content is 17%-19%, the total sugar (the total amount of invert sugar and sucrose) content is 68-72%, and the invert sugar content is below 30%, the sand return phenomenon will occur to varying degrees. If the water content in the finished product reaches 23%-28%, the total sugar content is about 60%, and the proportion of invert sugar in the total sugar reaches more than 90%, the sugar flow phenomenon will occur to varying degrees. Therefore, controlling the moisture content of the product and the composition of sugar is the key to controlling the sugar flow and sand return.

[0005] However, sugar flow and sand return often occur after a certain storage time. During storage, there are many changes such as sucrose conversion, fructose and glucose degradation, and participation in the Maillard reaction. It is difficult to predict the change of product quality by determining the initial sugar composition of the sample. In addition, new functional sugars and sugar alcohols are increasingly widely used in candied fruit products, such as trehalose, maltose, sorbitol, etc., which will also cause sugar flow or sand return to varying degrees in candied fruit products due to the different saturated crystallinity and distribution and bonding states in candied fruit tissues. Trehalose is stable to acid and heat and has low hygroscopicity, maltose is easily acid-lyzed and hygroscopic, and sorbitol is a hygroscopic non-reducing sugar alcohol. This makes the methods of determining sugar content based on hydrochloric acid hydrolysis and redox methods, which are mainly sucrose, fructose, and glucose as detection targets, not applicable to the characterization of new products.

[0006] At present, candied strawberry processing is an important step. The addition of a large amount of sugar can remove some water on the one hand, increase the solid content and sweetness of the preserved fruit on the other hand, and make the preserved fruit plump and elastic. However, the distribution of sugar in the preserved fruit and the stable state of its combination with water vary depending on the characteristics of the raw materials, the type of sugar, the storage environment and other factors, which may cause sugar flow and sand return to varying degrees.

[0007] In recent years, a variety of detection equipment based on mechanics, optics, electromagnetism, and thermodynamics theory have been used to detect changes in the physical properties of food, including texture analyzers, low-field nuclear magnetic resonance, and X-ray diffraction. These instruments can display the appearance and phase changes of food, as well as the macroscopic and microscopic characteristics of the internal structure from different angles. As a preserved fruit product, candied and dried strawberries can measure the viscosity on the surface of strawberry preserved fruits in published related studies, and it is related to the sensory viscosity, indicating that it has the possibility of characterizing the increase in viscosity caused by sugar flow. As a means of analysis and detection, low-field nuclear magnetic resonance has been widely used in the study of moisture state and migration, but the correspondence between the moisture state in preserved fruits and the phenomenon of sugar flow and sand return is still unknown.

[0008] In view of this, the art urgently needs a method for quantitatively characterizing the sugar flow and sand return phenomenon in strawberry preserves to provide guidance for the sugar flow and sand return in the processing of strawberry preserves. Summary of the invention

[0009] The purpose of the present invention is to provide a method for predicting, identifying, regulating or delaying the phenomenon of sugar flow and sand return in strawberry preserved fruits.

[0010] The present invention provides a method for controlling the phenomenon of sugar flow and sand return in dried strawberry, comprising the following steps:

[0011] The strawberry preserves are prepared by soaking in sucrose; the phenomenon of sugar flow and sand return in the strawberry preserves is regulated by controlling the maturity level of the raw materials for making the strawberry preserves or whether trehalose is added during soaking;

[0012] The raw material maturity level of strawberry preserves is low, and the prepared strawberry preserves are prone to sandiness. During the soaking process, the maturity level of the strawberry raw material is increased to delay sandiness.

[0013] The raw materials for making preserved strawberries have a high maturity level, and the prepared preserved strawberries are prone to sugar leakage. During the soaking process, the maturity level of the raw materials can be reduced to delay sugar leakage or trehalose can be added to delay sugar leakage.

[0014] The maturity levels of the raw materials for making preserved strawberries are as follows: strawberries in the powdery stage < strawberries in the half-red stage < strawberries in the nearly full red stage < strawberries in the full red stage;

[0015] For strawberries in the powder stage: red area <10%, single fruit weight 6-8g;

[0016] The strawberry in the half-red stage has a red area of ​​40%-50% and a single fruit weight of 10-12g;

[0017] The strawberry in the nearly full red stage has a red area of ​​80%-90% and a single fruit weight of 13-15g;

[0018] The strawberry in the full red stage has a red area of ​​100% and a single fruit weight of 15-20g.

[0019] Preferably, when trehalose is added to delay sugar flow, the total amount of the trehalose and the sucrose added is 40% of the mass of the strawberry; increasing the maturity level of the strawberry raw material to nearly full red strawberries can delay the occurrence of sugar flow or sand reversal.

[0020] The present invention also provides a method for predicting or identifying the phenomenon of sugar flow and sand return in dried strawberry, comprising the following steps:

[0021] (1) The preserved strawberries were tested by low-field nuclear magnetic resonance before and during storage to obtain the relaxation peak height of immobile water;

[0022] (2) When the relaxation peak height ratio of the non-flowing water of the preserved strawberries during storage and the preserved strawberries not stored increases, the sugar flow phenomenon occurs; when the relaxation peak height ratio of the non-flowing water of the preserved strawberries during storage and the preserved strawberries not stored decreases, the sand return phenomenon occurs.

[0023] Preferably, the raw materials for making preserved strawberries include strawberries in the powdery stage, half-red stage, nearly fully red stage and fully red stage; and the preserved strawberries are preserved strawberries impregnated with sucrose or a combination containing sucrose.

[0024] Preferably, the sucrose-containing combination includes any one of a trehalose+sucrose combination, a sorbitol+sucrose combination, and a sorbitol+sucrose combination;

[0025] The strawberry in the pollen-hanging period: red area <10%, single fruit weight 6-8g;

[0026] The strawberry in the half-red stage has a red area of ​​40%-50% and a single fruit weight of 10-12g;

[0027] The strawberry in the nearly full red stage has a red area of ​​80%-90% and a single fruit weight of 13-15g;

[0028] The strawberry in the full red stage has a red area of ​​100% and a single fruit weight of 15-20g.

[0029] Preferably, when the preserved strawberries are preserved strawberries soaked in sucrose, the relaxation peak height ratio rises to more than 173.91%, and sugar flow occurs;

[0030] When the preserved strawberry is preserved strawberry soaked in a combination of trehalose and sucrose, the relaxation peak height ratio drops below 92.16%, and the phenomenon of sand return occurs;

[0031] When the preserved strawberries are preserved strawberries soaked in a combination of sorbitol and sucrose, the relaxation peak height ratio rises to more than 127.43%, and sugar flow occurs;

[0032] When the preserved strawberries are preserved strawberries soaked in a combination of sorbitol and sucrose, the relaxation peak height ratio rises to more than 104.61%, and sugar flow occurs.

[0033] The present invention also provides the use of trehalose or sorbitol in regulating the phenomenon of sugar flow and sand return in strawberry dried fruit.

[0034] The present invention also provides the use of a combination of trehalose+sucrose or a combination of sorbitol+sucrose in delaying the phenomenon of sugar flow and sand return in preserved strawberries.

[0035] The present invention also provides a method for delaying the phenomenon of sugar flow and sand return in strawberry preserved food, comprising the following steps:

[0036] (1) Selecting frozen strawberries with 100% red area and a single fruit weight of 15 to 20 g, adding a food-grade sodium sulfite solution with a mass volume concentration of 0.2 to 0.4%, soaking at room temperature for 2.5 to 3.5 hours, taking out the strawberries, draining the solution on the surface of the strawberries, and obtaining thawed strawberries;

[0037] (2) adding solid sugar and thawed strawberries, mixing and sealing;

[0038] (3) After candied for 70 to 74 hours, remove the strawberries and dry them to obtain preserved strawberries.

[0039] Preferably, the variety of the strawberry includes the Monterey variety, the solid sugar includes trehalose + sucrose or sorbitol + sucrose, the drying method is drying at 55-65° C. for 10-12 hours; the added mass ratio of the trehalose and sucrose is 1:3; the mass ratio of the sorbitol and sucrose is 5:3; the added amount of the solid sugar is 40% of the mass of the thawed strawberries.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The invention provides a method for regulating the sugar flow and sand return phenomenon of strawberry preserved food. The sugar flow and sand return phenomenon of strawberry preserved food is regulated by controlling the maturity level of raw materials for making the strawberry preserved food or whether trehalose is added during soaking. The sugar flow or sand return phenomenon can be effectively delayed by adding trehalose during soaking and controlling the coloring area of ​​the strawberry to be 80%-90%.

[0042] The present invention also provides a method for predicting or identifying the phenomenon of sugar flow and sand return in strawberry preserved meat. Based on the difference in maturity of strawberry fruits and sugar used for soaking, strawberry preserved meat samples with different degrees of sugar flow and sand return are obtained through storage for a period of time. The texture characteristics such as hardness and viscosity of the strawberry preserved meat and data such as water freedom degree are obtained by using a texture analyzer and low-field nuclear magnetic resonance technology. Combined with the definition of the phenomenon of sugar flow and sand return by sensory convection, the physical definition range of sugar flow and sand return in strawberry preserved meat is determined, which provides a method for controlling sugar flow and sand return in the processing of strawberry preserved meat.

[0043] The present invention also provides the use of trehalose or sorbitol in regulating the phenomenon of sugar flow and sand return in strawberry preserved. The present invention significantly delays the time when the sugar flow and sand return phenomenon occurs in strawberry preserved by combining trehalose + sucrose or sorbitol + sucrose.

[0044] The present invention also provides a method for preparing preserved strawberries. The preserved strawberries prepared according to the method can delay the occurrence of sugar flow and sand return by more than 30 days during the storage period. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 These are the NMR inversion spectra of preserved strawberries impregnated with different sugars according to Examples 1 to 4.

[0046] Figure 2 These are the NMR inversion spectra of three preserved strawberries of different maturity in Example 5. DETAILED DESCRIPTION

[0047] The present invention provides a method for controlling the phenomenon of sugar flow and sand return in dried strawberry, comprising the following steps:

[0048] The strawberry preserves are prepared by soaking in sucrose; the phenomenon of sugar flow and sand return in the strawberry preserves is regulated by controlling the maturity level of the raw materials for making the strawberry preserves or whether trehalose is added during soaking;

[0049] The raw material maturity level of strawberry preserves is low, and the prepared strawberry preserves are prone to sandiness. During the soaking process, the maturity level of the strawberry raw material is increased to delay sandiness.

[0050] The raw materials for making preserved strawberries have a high maturity level, and the prepared preserved strawberries are prone to sugar leakage. During the soaking process, the maturity level of the raw materials can be reduced to delay sugar leakage or trehalose can be added to delay sugar leakage.

[0051] The maturity levels of the raw materials for making preserved strawberries are as follows: strawberries in the powdery stage < strawberries in the half-red stage < strawberries in the nearly full red stage < strawberries in the full red stage;

[0052] For strawberries in the powder stage: red area <10%, single fruit weight 6-8g;

[0053] The strawberry in the half-red stage has a red area of ​​40%-50% and a single fruit weight of 10-12g;

[0054] The strawberry in the nearly full red stage has a red area of ​​80%-90% and a single fruit weight of 13-15g;

[0055] The strawberry in the full red stage has a red area of ​​100% and a single fruit weight of 15-20g.

[0056] In the present invention, when trehalose is added to delay the flow of sugar, the total amount of the trehalose and the sucrose added is preferably 40% of the mass of the strawberry. The weight ratio of the trehalose and the sucrose added can be conventionally selected according to actual needs. As an embodiment, when the preserved strawberry is a preserved strawberry soaked in a sucrose-containing combination, the weight ratio of the trehalose and the sucrose added is preferably 1:3.

[0057] In the present invention, when the maturity level of the raw materials for making preserved strawberries is used to regulate sugar flow and sand return, the maturity level of the strawberry raw materials is increased to strawberries that are nearly fully red, which can delay the occurrence of sugar flow or sand return.

[0058] In the present invention, as an implementable embodiment, the method for impregnating preserved strawberries with sucrose or a combination containing sucrose comprises the following steps:

[0059] (1) selecting raw materials for making preserved strawberries, freezing strawberries, adding a food-grade sodium sulfite solution with a mass volume concentration of 0.2 to 0.4%, soaking the strawberries at room temperature for 2.5 to 3.5 hours, removing the strawberries, draining the solution on the surface of the strawberries, and obtaining thawed strawberries;

[0060] (2) adding sucrose or a combination containing sucrose to the thawed strawberries and mixing them, and sealing;

[0061] (3) After candied for 70 to 74 hours, remove the strawberries and dry them to obtain preserved strawberries.

[0062] The strawberry variety preferably includes Monterey, and more preferably Monterey strawberry. The mass volume concentration of the food-grade sodium sulfite solution is preferably 0.25-0.35%, and more preferably 0.3%. The room temperature is 25° C. The soaking time is preferably 3 hours.

[0063] In the present invention, during drying, the single layer is placed on a hot air drying oven tray and dried at 60° C. for 12 hours to obtain preserved strawberries.

[0064] The present invention also provides a method for predicting or identifying the phenomenon of sugar flow and sand return in dried strawberry, comprising the following steps:

[0065] (1) The preserved strawberries were tested by low-field nuclear magnetic resonance before and during storage to obtain the relaxation peak height of immobile water;

[0066] (2) When the relaxation peak height ratio of the non-flowing water of the preserved strawberries during storage and the preserved strawberries not stored increases, the sugar flow phenomenon occurs; when the relaxation peak height ratio of the non-flowing water of the preserved strawberries during storage and the preserved strawberries not stored decreases, the sand return phenomenon occurs.

[0067] In the present invention, the raw materials for making preserved strawberries include strawberries in the powdery stage, half-red stage, nearly fully red stage and fully red stage; the preserved strawberries are preserved strawberries soaked in sucrose or a combination containing sucrose.

[0068] In the present invention, the sucrose-containing combination preferably includes any one of a trehalose+sucrose combination, a maltose+sucrose combination, and a sorbitol+sucrose combination.

[0069] The raw materials for making preserved strawberries of the present invention include:

[0070] The strawberry in the pollen-hanging period: red area <10%, single fruit weight 6-8g;

[0071] The strawberry in the half-red stage has a red area of ​​40%-50% and a single fruit weight of 10-12g;

[0072] The strawberry in the nearly full red stage has a red area of ​​80%-90% and a single fruit weight of 13-15g;

[0073] The strawberry in the full red stage has a red area of ​​100% and a single fruit weight of 15-20g.

[0074] When the present invention predicts or identifies the phenomenon of sugar flow and sand return in strawberry preserved fruit,

[0075] When the preserved strawberries are preserved strawberries soaked in sucrose, the relaxation peak height ratio rises to more than 173.91%, and sugar flow occurs;

[0076] When the preserved strawberry is preserved strawberry soaked in a combination of trehalose and sucrose, the relaxation peak height ratio drops below 92.16%, and the phenomenon of sand return occurs;

[0077] When the preserved strawberry is preserved strawberry soaked in a combination of maltose and sucrose, the relaxation peak height ratio rises to more than 127.43%, and sugar flow occurs;

[0078] When the preserved strawberries are preserved strawberries soaked in a combination of sorbitol and sucrose, the relaxation peak height ratio rises to more than 104.61%, and sugar flow occurs.

[0079] In the present invention, the unstored preserved strawberries refer to the initial state when the preserved strawberries sample is prepared.

[0080] In the present invention, when predicting or identifying the phenomenon of sugar flow and sand return in strawberry preserved, the method for preparing the strawberry preserved comprises the following steps:

[0081] (1) Select frozen strawberries, add a food-grade sodium sulfite solution with a mass volume concentration of 0.2-0.4%, soak at room temperature for 2.5-3.5 hours, remove the strawberries, drain the solution on the surface of the strawberries, and obtain thawed strawberries;

[0082] (2) adding sucrose or a combination containing sucrose to the thawed strawberries and mixing them, and sealing;

[0083] (3) After candied for 70 to 74 hours, remove the strawberries and dry them to obtain preserved strawberries.

[0084] In the present invention, the strawberry variety preferably includes Monterey, and more preferably Monterey variety strawberry. The mass volume concentration of the food-grade sodium sulfite solution is preferably 0.25-0.35%, and more preferably 0.3%. The room temperature is 25°C. The soaking time is preferably 3h. The total amount of sucrose or a sucrose-containing combination added is 40% of the mass of the thawed strawberries. The mass volume ratio of the strawberries to the food-grade sodium sulfite solution with a mass volume concentration of 0.3% is preferably 2g:3mL. The sucrose-containing combination includes: any one of a trehalose + sucrose combination, a maltose + sucrose combination, or a sorbitol + sucrose combination.

[0085] In the present invention, the candied time is preferably 71 to 73 hours, more preferably 72 hours. The drying method is drying at 55 to 65°C for 10 to 12 hours, more preferably 60°C for 12 hours; the drying further comprises placing the strawberries to be dried in a single layer on a hot air drying oven tray.

[0086] In the present invention, the moisture state of the preserved strawberries is determined by low-field nuclear magnetic resonance at 0 day after being sealed and moistened, and after being stored at 25°C for 30 days, 90 days, and 120 days. In the present invention, the detection of the low-field nuclear magnetic inversion spectrum includes the following steps:

[0087] The whole strawberry preserves were placed on a 60mm NMR special polytetrafluoroethylene tube and placed in the center area of ​​a magnetic field with a diameter of 60mm, a magnetic field strength of 0.5T, a magnetic field temperature of 32°C, and a main frequency of 21.0MHz. The center frequency was determined under the FID sequence, and the 90° and 180° pulse widths were found to collect CPMG relaxation signals. As an implementable method, the relaxation signal acquisition parameters are: 90 pulse and 180 pulse times are 24.48μs and 40.0μs, respectively, the repeated waiting time Tw between two scans is 4000ms, the analog gain RG1 is 20, the digital gain DRG1 is 3, the preamplification gain PRG is 0, the number of echoes NECH is 15000, and the cumulative number Ns is 16. Multi Exp InvAnalysis software was used to perform multi-exponential fitting of CPMG relaxation data in combination with iterative reconstruction technology, and the number of iterations was 100000. Through fitting, the relaxation time, peak area, and the proportion of each peak area to the total peak area were obtained.

[0088] The present invention also provides the use of trehalose or sorbitol in regulating the phenomenon of sugar flow and sand return in strawberry dried fruit.

[0089] In the present invention, the preserved strawberry is obtained by dipping strawberries with 100% red area in full red stage; the preserved strawberry is preserved strawberry dipped in sucrose. If the preserved strawberry after sucrose dipping has sugar flow, trehalose and / or sorbitol can be added during sucrose dipping to alleviate the problem.

[0090] The present invention also provides the use of a combination of trehalose + sucrose or a combination of sorbitol + sucrose in delaying the phenomenon of sugar flow and sand return in preserved strawberries. In the present invention, preserved strawberries soaked in sucrose alone showed sugar flow in 30 days, while in the combination of trehalose + sucrose, when the mass ratio of trehalose to sucrose was 1:3, the phenomenon of sand return was delayed from 30 days to 120 days in preserved strawberries. In the present invention, in the combination of sorbitol + sucrose, when the mass ratio of sorbitol to sucrose was 5:3, the phenomenon of sugar flow was delayed from 30 days to 90 days in preserved strawberries.

[0091] The present invention also provides a method for preparing preserved strawberries, comprising the following steps:

[0092] (1) Selecting frozen strawberries with 100% red area and a single fruit weight of 15-20 g, adding a food-grade sodium sulfite solution with a mass volume concentration of 0.2-0.4%, soaking at room temperature for 2.5-3.5 hours, taking out the strawberries, draining the solution on the surface of the strawberries, and obtaining thawed strawberries;

[0093] (2) adding solid sugar and thawed strawberries, mixing and sealing;

[0094] (3) After candied for 70 to 74 hours, remove the strawberries and dry them to obtain preserved strawberries.

[0095] The variety of strawberry in the present invention is preferably Monterey variety strawberry. The solid sugar includes trehalose + sucrose or sorbitol + sucrose, and the drying method is 55-65°C for 10-12h; the mass ratio of trehalose and sucrose is 1:3; the mass ratio of sorbitol and sucrose is 5:3; the amount of solid sugar added is 40% of the mass of the thawed strawberry.

[0096] In the present invention, the sucrose is white granulated sugar, the trehalose is trehalose powder, the maltose is maltose powder, and the sorbitol is sorbitol powder.

[0097] In order to further illustrate the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0098] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the materials and reagents used are all reagents and materials that can be obtained from commercial channels unless otherwise specified.

[0099] The four strawberries of different maturity described in the following embodiment are strawberries in the powder stage, strawberries in the half-red stage, strawberries in the nearly full red stage and strawberries in the fully red stage; the maturity levels from low to high are strawberries in the powder stage < strawberries in the half-red stage < strawberries in the nearly full red stage < strawberries in the fully red stage. Among them, strawberries in the powder stage: red area <10%, single fruit weight 6-8g; strawberries in the half-red stage: red area 40%-50%, single fruit weight 10-12g; strawberries in the nearly full red stage: red area 80%-90%, single fruit weight 13-15g; strawberries in the fully red stage: red area 100%, single fruit weight 15-20g.

[0100] Example 1

[0101] A method for characterizing and predicting the flow and return of sugar in strawberry preserved vegetables based on physical properties mainly comprises the following steps:

[0102] 1) Select 200g of frozen Monterey strawberries with 100% red area and a single fruit weight of 15-20g;

[0103] 2) Add 300 mL of food-grade sodium sulfite solution with a mass volume concentration of 0.3% and soak at room temperature for 3 hours until thawed;

[0104] 3) After the strawberries are thawed, remove them, drain the solution, and transfer them to the candied jar;

[0105] 4) Add 80g of white sugar and mix with strawberries, and seal;

[0106] 5) After candiing at room temperature for 72 hours, remove the strawberries, place them in a single layer on a tray in a hot air drying oven, and dry them at 60° C. for 12 hours to obtain preserved strawberries;

[0107] Example 2

[0108] The difference from Example 1 is that 60 g of white sugar and 20 g of trehalose powder are selected in step 4).

[0109] Example 3

[0110] The difference from Example 1 is that 50 g of white sugar and 30 g of maltose powder are selected in step 4).

[0111] Example 4

[0112] The difference from Example 1 is that 30 g of white sugar and 50 g of sorbitol powder are selected in step 4).

[0113] Example 5

[0114] The difference from Example 1 is that in step 1), three strawberries of different maturity are selected, each weighing 200 g, namely, the powdery stage: the red area is less than 10%, and the single fruit weight is 6-8 g; the half-red stage: the red area is 40%-50%, and the single fruit weight is 10-12 g; the nearly full red stage strawberry with a red area of ​​80%-90%, and the single fruit weight is 13-15 g.

[0115] Test Example 1

[0116] On the 0th day after the preserved strawberries were sealed and moistened, and after being stored at 25°C for 30 days, 90 days and 120 days, the moisture status was determined by low-field nuclear magnetic resonance, the viscosity value was determined by a texture analyzer, and the water status was determined by low-field nuclear magnetic resonance.

[0117] 1. Determination of low-field nuclear magnetic relaxation spectrum of preserved strawberry

[0118] The specific measurement method is as follows: put the preserved strawberry on a 60mm NMR special polytetrafluoroethylene tube, and place it in the center area of ​​a magnetic field with a diameter of 60mm, a magnetic field strength of 0.5T, a magnetic field temperature of 32℃, and a main frequency of 21.0MHz. Determine the center frequency and find the 90° and 180° pulse widths under the FID sequence, and collect the Carr-Purcell-Meiboom-Gill sequence (CPMG) relaxation signal. Signal acquisition parameters: 90 pulse and 180 pulse times are 24.48μs and 40.0μs respectively, the repetition waiting time Tw between two scans is 4000ms, the analog gain RG1 is 20, the digital gain DRG1 is 3, the preamplification gain PRG is 0, the number of echoes NECH is 15000, and the number of accumulations Ns is 16. Multi Exp InvAnalysis software is used to perform multi-exponential fitting on the CPMG relaxation data in combination with iterative reconstruction technique (SIRT), and the number of iterations is 100000. Through fitting, the relaxation time, peak area and the ratio of each peak area to the total peak area were obtained. Five strawberries were measured in each group.

[0119] 2. Full spectrum texture determination of preserved strawberries

[0120] The specific method is as follows: the strawberry is placed sideways on the Brookfield CT3 texture analyzer base, and the probe TA39 is used for full spectrum analysis. Compression mode measurement, trigger point load 7g, test speed 0.50mm / s, compression distance 1mm, cycle number 2. Each group of samples is tested with 9 strawberries.

[0121] 3. Determination of sugar content in preserved strawberries

[0122] The specific determination method is: GB 5009.8-2023 Determination of fructose, glucose, sucrose, maltose and lactose in food Method 1: High performance liquid chromatography. Among them, fructose, glucose and maltose are reducing sugars, and sucrose, trehalose and sorbitol are non-reducing sugars.

[0123] The above test results show that:

[0124] Changes in low-field nuclear magnetic resonance (NMR) inversion spectra of preserved strawberries soaked in different sugars and sugar alcohols during storage for 120 days Figure 1 As shown. NMR inversion spectrum ( Figure 1) reflects the changes in water in different states. According to the signal strength and relaxation time, three peaks appear in the spectrum. According to the relaxation time corresponding to the peak apex, they are recorded as T21, T22, and T23 from small to large. The areas of the three spectrum peaks are A21, A22, and A23 respectively. The larger the relaxation time, the higher the degree of freedom of water. The higher the degree of freedom, the easier it is to lose water. The three peaks correspond to bound water, immobile water, and free water, respectively. The peak area ratio corresponds to the ratio of each form of water.

[0125] Analysis of the relaxation peak A22 of the main water form shows that only the changes in the spectra of sucrose impregnation (Example 1), maltose and sucrose mixed impregnation (Example 3), and sorbitol and sucrose mixed impregnation (Example 4) are similar, that is, the spectra shift to the left in chronological order and the peak height increases (values ​​are shown in Table 1), and the peak area of ​​different samples first decreases and then increases during storage, with the peak area value of 0 day being 100%, and the peak area change is between 93.84% and 100.57%. Only the peak height and peak area of ​​trehalose and sucrose mixed impregnation (Example 2) show a downward trend.

[0126] The peak height and peak area results of the non-mobile water in the low-field nuclear magnetic resonance (NMR) inversion spectra of preserved strawberries soaked in different sugars are shown in Table 1; the texture parameters and free sugar content of preserved strawberries are shown in Table 3.

[0127] Table 1 Peak height and peak area of ​​immobile water in low-field nuclear magnetic resonance (NMR) inversion spectra of preserved strawberries soaked in different sugars

[0128]

[0129] Attached Figure 2 The following are the low-field nuclear magnetic resonance (NMR) inversion spectra of preserved strawberries of three different degrees of maturity. It can be seen that the main component of preserved strawberries is non-flowing water, and the corresponding peak area is A22. Analysis of the relaxation time and peak area changes of non-flowing water shows that the relaxation time of the three degrees of maturity is arranged in the order of powder < half red < full red at 0d and 30d. The left shift of the sample spectrum after storage indicates that the degree of freedom of water is reduced. According to the peak apex time, the relaxation time is reduced from 3.409 to 2.41, 5.17 to 3.41, and 12.75 to 9.66. In addition, the signal intensity decreases, and the main manifestation is a decrease in peak height (see Table 2 for values), which are 72.52% and 95.49% of 0d, respectively, but the performance of the full red period is an increase in peak height, which is 120.76% of 0d. However, from the perspective of peak area, the peak area is still close. After 30 days of storage, the peak areas of preserved strawberries of the three degrees of maturity are 92.52%-99.28% of 0d.

[0130] It can be seen from the data results in Tables 1 and 2 of Examples 1-3 and Example 4 that not all kinds of strawberry preserves prepared by combining sugar with sucrose can prolong the time of the onset of sugar flow and sand return. The trehalose + sucrose combination in Example 2 can delay the onset of sand return to 120 days, and the sorbitol + sucrose combination in Example 4 can delay the onset of sugar flow to 90 days.

[0131] Moreover, the hardness values ​​of both sugar flow and returned sand show an increasing trend, and it is impossible to distinguish sugar flow and returned sand based on the physical property characterization data. It can be seen that not any numerical value can be used as the physical property characterization data of the sugar flow and returned sand phenomenon, and has the effect of distinguishing sugar flow and returned sand.

[0132] Table 2 Peak height and peak area of ​​immobile water in low-field NMR inversion spectra of preserved strawberries of three different maturity

[0133]

[0134] Table 3 shows the hardness, adhesion and sugar content data of preserved strawberry samples. The hardness of Examples 1-3 and Example 4 increases with the extension of storage time, among which Example 2 has the largest increase. In terms of adhesion, Examples 1, 3, and 4 increase with time, among which Example 1 has the largest increase, while Example 2 first increases and then decreases. In terms of sugar content, the ratio of reducing sugar to total sugar is between 49.02% and 100.00%, among which Example 3 has the highest reducing sugar ratio, and Example 4 has the lowest reducing sugar ratio, and both have sugar flow phenomenon.

[0135] Table 3 Texture parameters and free sugar content of preserved strawberry samples

[0136]

[0137]

[0138] The samples in Example 5 mainly showed an increase in hardness and a decrease in adhesion, and the lower the maturity, the greater the change. In terms of sugar content, the ratio of reducing sugar to total sugar is between 64.36% and 84.38%. The reducing sugar ratios in Examples 2 and 3 showed an increasing trend during storage, but sugar flow occurred in Example 1 and sand returned in Example 2. Therefore, it can be considered that the occurrence of sugar flow and sand return is related to the properties of sugar and the properties related to the maturity of the strawberry itself. The traditional basis and measures based on the reducing sugar ratio are more suitable for products that are only candied with sucrose.

[0139] The data from the five examples show that the classic invert sugar ratio theory is more suitable for products soaked in sucrose only. Strawberries with low maturity are prone to sand return, while strawberries with high maturity are prone to sugar flow, which can be alleviated by adding some trehalose.

[0140] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for controlling the phenomenon of sugar flow and sand return in strawberry preserved food, characterized in that: The following steps are involved: The strawberry preserves are prepared by soaking in sucrose; the phenomenon of sugar flow and sand return in the strawberry preserves is regulated by controlling the maturity level of the raw materials for making the strawberry preserves or whether trehalose is added during soaking; The raw material for making preserved strawberries has a low maturity level, and the prepared preserved strawberries are prone to sandiness. Improving the maturity level of the raw strawberries during soaking can delay sandiness. The raw materials for making preserved strawberries have a high maturity level, and the prepared preserved strawberries are prone to sugar leakage. During the soaking process, the maturity level of the raw materials can be reduced to delay sugar leakage or trehalose can be added to delay sugar leakage. The maturity levels of the raw materials for making preserved strawberries are as follows: strawberries in the powdery stage < strawberries in the half-red stage < strawberries in the nearly full red stage < strawberries in the full red stage; For strawberries in the powder stage: red area <10%, single fruit weight 6-8g; The strawberry in the half-red stage has a red area of ​​40%-50% and a single fruit weight of 10-12g; The strawberry in the nearly full red stage has a red area of ​​80%-90% and a single fruit weight of 13-15g; The strawberry in the full red stage has a red area of ​​100% and a single fruit weight of 15-20g.

2. The method according to claim 1, characterized in that: When trehalose is added to delay sugar flow, the total amount of the trehalose and the sucrose added is 40% of the mass of the strawberry; increasing the maturity level of the strawberry raw material to nearly full red strawberries can delay the occurrence of sugar flow or sand reversal.

3. A method for predicting or identifying the phenomenon of sugar flow and sand return in strawberry preserved food, characterized in that: The following steps are involved: (1) The preserved strawberries were tested by low-field nuclear magnetic resonance before and during storage to obtain the relaxation peak height of immobile water; (2) When the relaxation peak height ratio of the non-flowing water of the preserved strawberries during storage and the preserved strawberries not stored increases, the sugar flow phenomenon occurs; when the relaxation peak height ratio of the non-flowing water of the preserved strawberries during storage and the preserved strawberries not stored decreases, the sand return phenomenon occurs.

4. The method according to claim 3, characterized in that The raw materials for making preserved strawberries include strawberries in the powdery stage, half-red stage, nearly fully red stage and fully red stage; the preserved strawberries are preserved strawberries soaked in sucrose or a combination of sucrose.

5. The method according to claim 4, characterized in that The sucrose-containing combination includes any one of a trehalose+sucrose combination, a maltose+sucrose combination, and a sorbitol+sucrose combination; The strawberry in the powder stage: red area <10%, single fruit weight 6-8g; The strawberry in the half-red stage has a red area of ​​40%-50% and a single fruit weight of 10-12g; The strawberry in the nearly full red stage has a red area of ​​80%-90% and a single fruit weight of 13-15g; The strawberry in the full red stage has a red area of ​​100% and a single fruit weight of 15-20g.

6. The method according to claim 4, characterized in that When the preserved strawberries are preserved strawberries soaked in sucrose, the relaxation peak height ratio rises to more than 173.91%, and sugar flow occurs; When the preserved strawberry is preserved strawberry soaked in a combination of trehalose and sucrose, the relaxation peak height ratio drops below 92.16%, and the phenomenon of sand return occurs; When the preserved strawberry is preserved strawberry soaked in a combination of maltose and sucrose, the relaxation peak height ratio rises to more than 127.43%, and sugar flow occurs; When the preserved strawberries are preserved strawberries soaked in a combination of sorbitol and sucrose, the relaxation peak height ratio rises to more than 104.61%, and sugar flow occurs.

7. The application of trehalose or sorbitol in regulating the phenomenon of sugar flow and sand return in strawberry jerky.

8. The application of trehalose + sucrose combination or sorbitol + sucrose combination in delaying the phenomenon of sugar flow and sand return in strawberry preserves.

9. A method for delaying the phenomenon of sugar flow and sand return in strawberry preserved food, characterized in that: The following steps are involved: (1) Selecting frozen strawberries with 100% red area and a single fruit weight of 15 to 20 g, adding a food-grade sodium sulfite solution with a mass volume concentration of 0.2 to 0.4%, soaking at room temperature for 2.5 to 3.5 hours, taking out the strawberries, draining the solution on the surface of the strawberries, and obtaining thawed strawberries; (2) adding solid sugar and thawed strawberries, mixing and sealing; (3) After candied for 70 to 74 hours, remove the strawberries and dry them to obtain preserved strawberries.

10. The method according to claim 9, characterized in that The strawberry varieties include Monterey varieties, the solid sugar includes trehalose+sucrose or sorbitol+sucrose, the drying method is drying at 55-65°C for 10-12h; the added mass ratio of trehalose and sucrose is 1:3; the mass ratio of sorbitol and sucrose is 5:3; the added amount of the solid sugar is 40% of the mass of the thawed strawberries.

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