阅读说明：本技术 用于食品冷链安全监测的温敏型乳液指示剂的制备方法 (Preparation method of temperature-sensitive emulsion indicator for food cold chain safety monitoring ) 是由 王然 孙佳帝 刘洋 张春玉 蔡勇 温慧颖 刘颖 李亚茹 徐亚杰 于 2019-11-04 设计创作，主要内容包括：本发明公开了用于食品冷链安全监测的温敏型乳液指示剂的制备方法,采用如下实施步骤：步骤1,温敏型低温激发油相的制备；步骤2,温感调控油相的制备；步骤3,温敏型乳液指示剂的制备；本发明把在化工、能源、医药等领域广泛使用的皮克林乳液应用到食品冷链系统监测中,利用油脂粒子控制乳液的稳定性,制成以皮克林乳液为基质的温敏型乳液指示剂,适用于监测水产品、畜产品和农产品等所有需要冷藏的食品、食品原料和食品半成品的冷链质量安全,对于冷链物流企业提高食品质量管理意识以及提高冷链系统管理方法和手段均具有积极的促进意义。(The invention discloses a preparation method of a temperature-sensitive emulsion indicator for monitoring food cold chain safety, which comprises the following implementation steps: step 1, preparing a temperature-sensitive low-temperature excitation oil phase; step 2, preparing a temperature-sensitive regulating oil phase; step 3, preparing a temperature-sensitive emulsion indicator; the Pickering emulsion widely used in the fields of chemical industry, energy, medicine and the like is applied to monitoring of a food cold chain system, the stability of the emulsion is controlled by using the grease particles, and the temperature-sensitive emulsion indicator taking the Pickering emulsion as a matrix is prepared.)

1. The preparation method of the temperature-sensitive emulsion indicator for monitoring the food cold chain safety is characterized by comprising the following steps: the method comprises the following steps:

step 1, preparing a temperature-sensitive low-temperature excitation oil phase:

mixing yolk lecithin and lysolecithin in a ratio of 1: 6-1: 12 to serve as an oil phase, placing the oil phase in purified water at a mass concentration of 20% -60%, and carrying out ultrasonic treatment on the mixed solution containing the oil phase for 18-25 min by using an ultrasonic cell disruptor in an intermittent ultrasonic treatment mode of 6s intermittent 3s of ultrasound at a temperature of 25-45 ℃; homogenizing the mixed solution by a homogenizer at a speed of 12300r/min for 12-25 min; screening the mixed solution by using a laser particle size detector, wherein the particle size of the mixed solution is not more than 5 mu m;

step 2, preparing a temperature-sensing regulation oil phase:

adding oil-phase coconut oil into the mixed liquid obtained in the step (1) to ensure that the mass concentration of the coconut oil in the mixed liquid is 180-280%; carrying out ultrasonic treatment for 21-33 min by using an ultrasonic cell disruptor and adopting an intermittent ultrasonic treatment mode of 6s and 3s of ultrasonic intermittence at the temperature of 25-45 ℃; homogenizing the mixed solution by a homogenizer at a speed of 12500r/min for 18-24 min to prepare a high oil phase mixed solution; screening the high oil phase mixed liquid by using a laser particle size detector, wherein the particle size of the high oil phase mixed liquid is not more than 5 mu m;

step 3, preparing the temperature-sensitive emulsion indicator:

adding an emulsifier butyl stearate into the high oil phase mixed solution obtained in the step 2 to ensure that the mass concentration of the butyl stearate in the mixed solution is 180-280%; carrying out ultrasonic treatment for 12-24 min by using an ultrasonic cell disruptor and adopting an intermittent ultrasonic treatment mode of 6s and 3s of ultrasonic intervals under the condition of 25-45 ℃ to obtain a temperature-sensitive emulsion indicator; observing the type of the temperature-sensitive emulsion indicator by using a fluorescence inverted microscope, and screening the temperature-sensitive emulsion indicator to be of an oil-in-water type; screening the exothermic peak value and the endothermic peak value of the temperature-sensitive emulsion indicator by using a scanning calorimeter, wherein the exothermic peak value is not more than 5 ℃, and the endothermic peak value is not more than 15 ℃; screening a temperature-sensitive emulsion indicator by using a laser particle sizer at the temperature of 25 ℃, wherein the particle size of the temperature-sensitive emulsion indicator is not more than 5 mu m; the thermal separation effect of the temperature-sensitive emulsion indicator is screened by using a laser particle sizer, the temperature-sensitive emulsion indicator is placed at the temperature of 1-5 ℃ for 11 hours, then the temperature-sensitive emulsion indicator is placed in an environment with the temperature higher than 15 ℃ for 30 minutes, and the particle size of the emulsion after thermal separation is not less than 110 microns.

Technical Field

The invention belongs to the field of food cold chain safety, and particularly relates to a preparation method of a temperature-sensitive emulsion indicator for food cold chain safety monitoring.

Background

The food cold chain refers to a supply chain system in which refrigerated or frozen foods (including food raw materials and food semi-finished products) are subjected to specific low-temperature conditions in all links before production, storage, transportation, sale and consumption so as to ensure the quality and safety of the foods and prevent or reduce the deterioration, pollution and loss of the foods. Generally, the food to be stored and transported by the cold chain system is a temperature-sensitive perishable food, which has extremely strict requirements on the ambient temperature, and the fluctuation of the ambient temperature is a key factor threatening the quality and safety of the food. With time, various biochemical reactions occur in foods, which are mainly related to the growth and metabolism of microorganisms. The putrefying bacteria easy to parasitize in the refrigerated meat include pseudomonas, moraxella, micrococcus, lactobacillus, staphylococcus and the like; the putrefying bacteria which are easy to parasitize in the aquatic products comprise Shewanella putrefaciens, Aeromonas, phosphorescence luminescent bacillus, thermosoursoniella, pseudomonas, lactic acid bacteria and the like; the spoilage bacteria susceptible to parasitism in the dairy products include Pseudomonas, Enterobacteriaceae, Moraxellaceae, and Streptococcus. In the cold chain system, if the temperature of the environment where the food is located fluctuates, microorganisms in the food can wake up from dormancy and start to perform active growth, metabolism and reproduction activities, so that the quality of the food is degraded, such as protein decomposition, fat oxidation, toxin accumulation and loss of eating property, and the potential safety hazard generated can not be eliminated even if the deteriorated food is refrigerated or frozen again. However, at present, the food cold chain system in many areas of China is not perfect, cold chain infrastructure falls behind, cold chain transportation capacity is weak, cold chain organization and management measures are lagged behind, in addition, the food quality control of workers of some cold chain logistics enterprises and the control consciousness of agricultural product cold chain transportation are relatively weak, and the factors are very easy to cause temperature fluctuation of food in the circulation link, so that the food quality and safety cannot be guaranteed.

The government of China highly pays attention to the food cold chain safety problem, and in order to promote the healthy and standard development of the cold chain logistics industry and guarantee the consumption safety of fresh agricultural products and food, the office of the State department issues an opinion on accelerating the development of cold chain logistics, guaranteeing the food safety and promoting the consumption upgrade in 2017 month 4 to comprehensively guide the development and the improvement of a food cold chain system, wherein the government specifically mentions that the supervision on the temperature control record of each link of a cold chain and the product quality is enhanced. At present, in the aspect of detection of bacterial pathogens and harmful substances in food, the traditional detection method in China generally needs to culture and separate microorganisms under the condition of aseptic operation, and needs to carry out detection procedures such as biochemical experiment, serological identification, serological typing and the like. The whole inspection process not only consumes long time and has high cost, but also the detection method is only suitable for being adopted by special inspection mechanisms; however, since the food inspection skill has strong profession and ordinary consumers do not have the profession skill, the ordinary consumers cannot detect the food quality safety by using the traditional detection method. Therefore, when the refrigerated fresh food is purchased, a large number of ordinary consumers can only judge the refrigerated fresh food by the experience of the consumers, and the experience is easily influenced by human subjective factors and personal judgment ability of the consumers. According to investigations, 49% of the consumers visited in china think that they could tell whether the refrigerated food was properly stored in the store and during transport; shelf life is viewed by 74% of consumers; 70% of consumers will judge whether the food is fresh by touch or observation; there are 52% of consumers who only go to trusted or well known stores to purchase food. However, it is a real situation that most consumers cannot tell whether the food is safe and hygienic and whether it is properly stored and transported.

In view of the above situation, the invention discloses a preparation method of a temperature-sensitive emulsion indicator for food cold chain safety monitoring, the temperature-sensitive emulsion indicator prepared by the method can be sealed in a transparent packaging material and fixed in the food outer package, and the food packaging material at the fixed position is transparent, so that the change condition of the emulsion indicator can be observed conveniently. When the environmental temperature of food in the cold chain is changed within a certain range, the emulsion indicator can generate system phase transfer according to the change of the environmental temperature, and is used for indicating whether the refrigerated food is subjected to a 'hot' environment in a cold chain logistics system, so that the effect of monitoring the food cold chain safety is exerted. The emulsion indicator prepared by the invention has the characteristics of sensitive reaction and easy discrimination of detection results, and can enable ordinary consumers to know whether the food cold chain has over-temperature fluctuation or not. The method and the device are beneficial to exciting cold-chain logistics enterprises to improve food quality management awareness and cold-chain logistics system management methods and means, and have positive promoting significance for food safety monitoring work in China, physical health of China and the like.

Disclosure of Invention

The invention aims to provide a preparation method of a temperature-sensitive emulsion indicator, which has the advantages that raw materials are all food grade, the preparation method is simple, the temperature-sensitive emulsion indicator can be stored at room temperature before use, can be automatically excited at low temperature, can be automatically disintegrated at high temperature, and can generate an irreversible phase separation phenomenon after disintegration.

The technical scheme adopted by the invention is implemented according to the following steps.

Step 1, preparing a temperature-sensitive low-temperature excitation oil phase: mixing yolk lecithin and lysolecithin in a ratio of 1: 6-1: 12 to serve as an oil phase, placing the oil phase in purified water at a mass concentration of 20% -60%, and carrying out ultrasonic treatment on the mixed solution containing the oil phase for 18-25 min by using an ultrasonic cell disruptor in an intermittent ultrasonic treatment mode of 6s intermittent 3s of ultrasound at a temperature of 25-45 ℃; homogenizing the mixed solution by a homogenizer at a speed of 12300r/min for 12-25 min; and screening the mixed solution by using a laser particle size detector, wherein the particle size of the mixed solution is not more than 5 mu m.

Step 2, preparing a temperature-sensing regulation oil phase: adding oil-phase coconut oil into the mixed liquid obtained in the step (1) to ensure that the mass concentration of the coconut oil in the mixed liquid is 180-280%; carrying out ultrasonic treatment for 21-33 min by using an ultrasonic cell disruptor and adopting an intermittent ultrasonic treatment mode of 6s and 3s of ultrasonic intermittence at the temperature of 25-45 ℃; homogenizing the mixed solution by a homogenizer at a speed of 12500r/min for 18-24 min to prepare a high oil phase mixed solution; and screening the high oil phase mixed liquid by using a laser particle size detector, wherein the particle size of the high oil phase mixed liquid is not more than 5 mu m.

Step 3, preparing the temperature-sensitive emulsion indicator: adding an emulsifier butyl stearate into the high oil phase mixed solution obtained in the step 2 to ensure that the mass concentration of the butyl stearate in the mixed solution is 180-280%; carrying out ultrasonic treatment for 12-24 min by using an ultrasonic cell disruptor and adopting an intermittent ultrasonic treatment mode of 6s and 3s of ultrasonic intervals under the condition of 25-45 ℃ to obtain a temperature-sensitive emulsion indicator; observing the type of the temperature-sensitive emulsion indicator by using a fluorescence inverted microscope, and screening the temperature-sensitive emulsion indicator to be of an oil-in-water type; screening the exothermic peak value and the endothermic peak value of the temperature-sensitive emulsion indicator by using a scanning calorimeter, wherein the exothermic peak value is not more than 5 ℃, and the endothermic peak value is not more than 15 ℃; screening a temperature-sensitive emulsion indicator by using a laser particle sizer at the temperature of 25 ℃, wherein the particle size of the temperature-sensitive emulsion indicator is not more than 5 mu m; the thermal separation effect of the temperature-sensitive emulsion indicator is screened by using a laser particle sizer, the temperature-sensitive emulsion indicator is placed at the temperature of 1-5 ℃ for 11 hours, then the temperature-sensitive emulsion indicator is placed in an environment with the temperature higher than 15 ℃ for 30 minutes, and the particle size of the emulsion after thermal separation is not less than 110 microns.

The temperature-sensitive emulsion indicator comprises the following components: a mixture of yolk lecithin and lysolecithin with a mass concentration of 20-60%, wherein the ratio of the yolk lecithin to the lysolecithin is 1: 6-1: 12; coconut oil with the mass concentration of 180-280 percent, butyl stearate with the mass concentration of 180-280 percent and the balance of purified water.

The working mechanism of the temperature-sensitive emulsion indicator for monitoring the cold chain safety of food is as follows: the temperature-sensitive emulsion indicator prepared by the invention and used for monitoring food cold chain safety is Pickering emulsion. The pickering emulsion is a relatively stable emulsion dispersion system formed by inhibiting coalescence of oil drops by utilizing nano particles or micro particles with high surface energy and adsorption effect of the nano particles or the micro particles on an oil-water interface. The temperature-sensitive type emulsion indicator comprises the components of egg yolk lecithin, lysolecithin, coconut oil, butyl stearate and purified water, and the raw materials are all food-grade. Wherein the egg yolk lecithin is a phospholipid substance composed of glycerol, choline, phosphoric acid, saturated and unsaturated fatty acids; lysolecithin is a single-chain fatty acyl phospholipid derivative generated by hydrolysis or enzymolysis of one-bit or two-bit ester bond of lecithin; the egg yolk lecithin and the lysolecithin both have certain surface activity properties, wherein two acyl chains exist in the egg yolk lecithin molecule, a sheet structure is easily formed at low temperature, and further the interface structure of the emulsion is destroyed, so that the temperature-sensitive emulsion indicator is beneficial to realizing the phenomenon of phase separation visible to naked eyes after being heated; the lysolecithin has only one acyl chain, the addition ratio of the lysolecithin to the egg yolk lecithin is one of the main factors for realizing cold excitation of the emulsion indicator, and the temperature of the cold excitation can be adjusted. The coconut oil is triglyceride taking lauric acid as a main component, is easy to form small crystals at low temperature, plays an important role in the collapse of an emulsion interface structure, and is another important factor for realizing cold excitation of the emulsion indicator; the cold excitation of the temperature sensitive emulsion indicator is a necessary condition for thermal disintegration, and when the environmental temperature of the emulsion indicator reaches the melting point of coconut oil, the emulsion indicator will disintegrate and phase separation phenomenon visible to naked eyes occurs. Butyl stearate is used as an emulsifier, has better thermal stability, is beneficial to shortening the temperature ranges of the freezing point and the melting point of the emulsion indicator, improves the sensitivity of the emulsion indicator to temperature, and further improves the sensitivity of the emulsion indicator to the temperature monitoring of a food cold chain system. The yolk lecithin and the lysolecithin are matched in proportion, then coconut oil is added, the yolk lecithin, the lysolecithin and the coconut oil serve as oil phases, butyl stearate serving as an emulsifier of a food additive serves as a water phase, the mixture of the materials is prepared into pickering emulsion in which micron-sized grease particles are uniformly dispersed in water by utilizing an ultrasonic treatment process and a homogenization treatment process, and the pickering emulsion can achieve the effects of keeping stable at room temperature, being automatically excited at low temperature and automatically generating irreversible collapse at high temperature, so that the temperature-sensitive type indicator can be used for monitoring the cold chain safety of food.

The invention has the beneficial effects that: the temperature-sensitive emulsion indicator can monitor whether the temperature fluctuation condition exists in the cold-chain logistics system or not, and further ensures the quality safety of food in the cold-chain logistics system. The invention applies Pickering emulsion widely used in the fields of chemical industry, energy, medicine and the like to the monitoring of a food cold chain system, only adopts five raw materials including water and a simple preparation method, controls the stability of the emulsion by using grease particles, and prepares a temperature-sensitive emulsion indicator taking the Pickering emulsion as a substrate; and the five components forming the temperature-sensitive emulsion indicator are all food grade, the temperature-sensitive emulsion indicator is placed in the food outer package, the temperature of a food cold chain system is monitored, and the temperature-sensitive emulsion indicator cannot cause quality change of food chemical components in the period, namely secondary pollution to food sanitation is avoided. In addition, the temperature-sensitive emulsion indicator has good stabilizing effect, can be stored at room temperature for a long time before use, namely before cold excitation, and does not generate unstable phenomena such as oil-water separation and the like; placing the emulsion indicator at a low temperature of 1-5 ℃, wherein the structure of the emulsion indicator begins to change, and the emulsion indicator finishes cold excitation after 11 hours; if the emulsion indicator after cold excitation is placed at the temperature of 15 ℃ for 30min, the emulsion indicator can generate macroscopic phase separation which is irreversible, which indicates that the temperature fluctuation of food in a cold chain system can cause inevitable hidden danger to the food quality safety. Therefore, the temperature-sensitive emulsion indicator is suitable for monitoring the cold chain safety of all foods, food raw materials and food semi-finished products needing to be refrigerated, such as aquatic products, livestock products, agricultural products and the like, and monitoring whether the foods are subjected to temperature fluctuation with the temperature exceeding 15 ℃ in a cold chain system or not so as to achieve the purpose of monitoring the quality safety of the food cold chain system. The method has positive promoting significance for improving food quality management consciousness and cold-chain logistics system management methods and means for cold-chain logistics enterprises, and meanwhile has certain promoting effects on guaranteeing food safety in China and promoting body health of people.

Drawings

FIG. 1 is a flow chart of the present invention.

FIG. 2 is a graph showing the occurrence of macroscopic phase separation of a temperature-sensitive emulsion indicator over time at a temperature of 15 ℃.

FIG. 3 is an oil phase distribution of a temperature sensitive emulsion indicator without cold excitation under a microscope.

Detailed Description

Please refer to fig. 1, fig. 2 and fig. 3.

Step 1: mixing yolk lecithin and lysolecithin in a ratio of 2:15 to obtain an oil phase, placing the oil phase in purified water at a mass concentration of 40%, and performing ultrasonic treatment on the mixed solution containing the oil phase for 18min by using an ultrasonic cell disruption instrument in an intermittent ultrasonic treatment mode of ultrasonic 6s and 3 s; homogenizing the mixed solution by a homogenizer at a speed of 12300r/min for 12-25 min; and screening the mixed solution by using a laser particle size detector, wherein the particle size of the mixed solution is not more than 5 mu m.

Step 2: adding oil-phase coconut oil into the mixed liquid obtained in the step 1 to ensure that the mass concentration of the coconut oil in the mixed liquid is 235 percent; carrying out ultrasonic treatment for 33min by using an ultrasonic cell disruptor and adopting an intermittent ultrasonic treatment mode of 6s and 3s of ultrasonic intervals at the temperature of 35 ℃; homogenizing the mixed solution by a homogenizer at a speed of 12500r/min for 24min to obtain a high oil phase mixed solution; and screening the high oil phase mixed liquid by using a laser particle size detector, wherein the particle size of the high oil phase mixed liquid is not more than 5 mu m.

And step 3: adding an emulsifier butyl stearate into the high oil phase mixed solution obtained in the step 2 to ensure that the mass concentration of the butyl stearate in the mixed solution is 245%; carrying out ultrasonic treatment for 12min by using an ultrasonic cell disruptor and adopting an intermittent ultrasonic treatment mode of 6s and 3s to obtain a temperature-sensitive emulsion indicator at the temperature of 35 ℃; observing the type of the temperature-sensitive emulsion indicator by using a fluorescence inverted microscope, and screening the temperature-sensitive emulsion indicator to be of an oil-in-water type; screening the exothermic peak value and the endothermic peak value of the temperature-sensitive emulsion indicator by using a scanning calorimeter, wherein the exothermic peak value is not more than 5 ℃, and the endothermic peak value is not more than 15 ℃; screening a temperature-sensitive emulsion indicator by using a laser particle sizer at the temperature of 25 ℃, wherein the particle size of the temperature-sensitive emulsion indicator is not more than 5 mu m; the thermal separation effect of the temperature-sensitive emulsion indicator is screened by using a laser particle sizer, the temperature-sensitive emulsion indicator is placed at the temperature of 1-5 ℃ for 11 hours, then the temperature-sensitive emulsion indicator is placed in an environment with the temperature higher than 15 ℃ for 30 minutes, and the particle size of the emulsion after thermal separation is not less than 110 microns.

Through the specific implementation steps, the temperature-sensitive emulsion indicator for monitoring the food cold chain safety is processed, and the oil phase distribution of the temperature-sensitive emulsion indicator is shown in figure 3.