KR930009512B1 - Indicator for time temperature using phospholipase - Google Patents

Abstract

The time-temperature indicator to indicate the degree of quality deterioration of frozen foods consists of lecithin as substrate, phospholipase as enzyme and pH indicator, which is a mixture of Bromothymol Blue, methyl red and neutral red. The substrate lecithin can keep a stable emulsion state for the enzyme reaction of the indicator to proceed at a uniform rate. When the indicator is practically applied to foods, it shows a high reproduciblity. By observing the color change according to the preset pH change of the indicator, consumers can easily recognize the degree of deterioration of foods with the naked eyes.

Description

Development of a New Time-Temperature Indicator Using Phospholipase

1 is the color change of the time-temperature indicator with pH change.

2 shows the change in pH caused by phospholipase over time at various temperatures.

3 is the time at which the indicator reaches pH 7.5 at each temperature.

The present invention relates to the development of a time-temperature indicator (Time-Temperature Indicator) showing a color change in accordance with the degree of deterioration of the quality of frozen foods over time and temperature changes. More specifically, the present invention relates to the development of a time-temperature indicator that can easily identify deterioration of food, consisting of a phospholipase, a lecithin as a substrate, and an indicator that changes color with pH.

Time-temperature indicators initiate food storage and allow the reaction of substrates and enzymes in the indicators to progress, thereby increasing the amount of fatty acids produced in the indicators and reducing the pH of the indicator contents as the food storage time elapses. When the pH reaches a preset pH corresponding to the point of deterioration of the food, the color of the indicator changes so that consumers can identify it by the pH indicator in the indicator, thereby visually identifying whether the stored food is deteriorated. It is to be done.

The time-temperature indicator of the invention can be used in particular for frozen foods. Generally, the deterioration of food is determined by the storage temperature and storage period, and even if it is within the expiration date, it can be changed according to the storage temperature, so the freshness of food cannot be guaranteed only by the storage period, especially in the case of frozen foods. It is not easy to identify the alteration of.

Conventional time-temperature indicators using lipases use lipases and triglycerides as substrates for this enzyme to change the color of the pH indicator in the indicator by the free fatty acids produced when the lipase acts on the triglycerides. It is possible to know the deterioration of food quality according to the change. However, since triglyceride has only a lipophilic group, the emulsion state is unstable and the enzyme reaction rate is not constant. Therefore, since the lipase time-temperature indicator does not proceed at a constant rate, the fatty acid produced by the enzyme reaction There is a large error in accuracy in predicting food deterioration by observing the color change of the indicator that changes with the amount of.

The indicator of the present invention improves this problem, and by using phospholipase instead of lipase as an enzyme and having a hydrophilic group and a lipophilic group at the same time as a substrate, the enzyme reaction of the indicator can proceed at a constant rate by using a lecithin having a relatively stable emulsion. By using a lecithin that is actually stable in food, the enzyme reaction of the indicator can be progressed at a constant rate, so that the reproducibility for application to the food is actually high, and the color change of the indicator can be clearly observed according to the set pH change. By using the present indicator liquid, it is easy for consumers to see whether the food is deteriorated. As the food storage period elapses, the amount of free fatty acid produced by the action of phospholipase in the indicator attached to the food increases, so that the color of the pH indicator changes when the pH of the reaction system decreases to a certain level. Therefore, by adjusting the concentration of the enzyme, the time of discoloration in the pH indicator by the amount of fatty acid produced is matched with the time when the deterioration of the food is recognized, thereby providing an appropriate time-temperature indicator suitable for each food. .

This time-temperature indicator is characterized by the use of lecithin with a stable emulsion state in order to keep the enzyme reaction rate constant. Compared with the conventional lipase time-temperature indicators tested with the control, the standard deviation of the enzyme reaction rate constant is small, which can greatly reduce the error prediction range and accurately recognize changes in the quality of frozen foods (see Table 1). ).

In addition, the present invention is characterized in that by using a combination of various indicators as the indicator liquid it is possible to clearly distinguish the color change at the pH corresponding to the color at the initial pH of the indicator and the point of time when food degradation is expected.

The indicator of the present invention may further contain an emulsion stabilizer such as deoxycholate, and may also contain an antifreeze such as sorbitol or glycerin to prevent the reaction system including the substrate from freezing even at the freezing temperature of the food.

In the time-temperature indicator of the present invention, bromothymol blue (10.1 g dissolved in 16 ml of 0.01 N NaOH solution and diluted to 250 ml) as a pH indicator, methyl red (0.2% W / V in 50% U / V ethanol) and Neutral red (0.1% W / V in 60% V / V ethanol) was used in combination.

In one embodiment, the initial pH of the time-temperature indicator according to the present invention was adjusted to 8.0 and the indicator component was adjusted such that the pH of the indicator was 7.5 at the time when food alteration was expected. As a result of a food degradation identification experiment by attaching the temperature-time indicator of the present invention to the storage of frozen pork, the quality of the food was directly measured during the storage period of frozen pork and the color change of the indicator of the present invention. The degree of deterioration of the food predicted by the symmetry was quite consistent.

The present invention will be described in detail by the following examples.

Example 1

The pH indicator (bromothymol blue: methyl red: neutral red, 8: 2: 0.1) prepared in the present invention showed a distinct color difference at pH 8.0 and pH 7.5 as shown in FIG. have.

Example 2

A reaction system based on lecithin and a reaction system based on olive oil as a control were prepared to measure the pH change (FIG. 2) over time after phospholipase and lipase were reacted, respectively. The resulting fatty acid was titrated with 0.1N sodium hydroxide solution standardized. The standard deviation of initial fatty acid production rate was obtained by repeated experiments for each temperature in the range of 30 ℃ -18 ℃ and compared with the products using lipase. Table 1

Enzyme titer was 1 unit for 1 minute to produce 1umole of fatty acid, 7.4 units of lipase and 4.8 units of phospholipase.

TABLE 1 Fatty acid production rate constant and standard deviation

Example 3

After sonicating 25 ml of lecithin solution (3%, W / V) for 3 minutes, 0.5 g of sodium deoxycholate was added to 20 ml of this solution as a stabilizer. 0.25 ml of 0.1 M Tris buffer was added. After mixing the pH indicator of the present invention (in the same ratio as in Example 1, 8ml: 2ml: 0.1ml), an antifreezing agent (15ml of 15% V / Vglycerol and 45.8g of sorbitol) was added to prevent the substrate from freezing. The pH was adjusted to 8.0, which was stored in frozen glass at various temperatures in the range of 30 ° C-18 ° C by adding 5ml of porporlipase in 5 ml of transparent glass bottles 1.5 cm in diameter and 6.0 cm in height.

The time to reach pH 7.5 at each temperature was measured and a graph (Figure 3) was created. Using this graph, it is possible to predict color change at any freezing temperature. Therefore, by adjusting the concentration of enzyme, it can be applied to various frozen foods by extending or shortening the time when the color change occurs.

Claims (2)

A time-temperature indicator for identifying deterioration of frozen foods comprising lecithin, phospholipase and pH indicator. 2. The time-temperature indicator of claim 1, wherein the pH indicator is a mixture of bromothymol blue, methyl red and neutral red.