Food coloring agent, also known as food coloring, is an important type of food additives, with a wide range of applications, and there are two main categories, i.e., natural food coloring and synthetic food coloring.

With the improvement of living standards, people are more and more concerned about food safety, synthetic pigments are gradually replaced by natural pigments, the development of safe and reliable natural pigments is of great practical significance to protect human health.

Rosehips, also known as Loropetalum, red hornbeam, etc., grow in tropical and subtropical arid areas, mainly produced in Lincang area in China, Guangdong, Guangxi and other places are also distributed. The calyx of rosehips is a fleshy structure, containing reducing sugars, proteins, organic acids, vitamins, a variety of amino acids, as well as minerals needed by the human body, which contains anthocyanins, phenols, aldehydes with significant antioxidant function, anthocyanin content of up to 14.5 g. The anthocyanin content of the calyx of the rosehips is also very high.

Modern medicine has proved that natural pigments, especially those extracted from plants, are not only safe but also have certain nutritional value. Rose aubergine pigment is a rare natural pigment, the extracted rose aubergine pigment as a food additive used in the food industry, the production of food is both safe and nutritious, is a promising development of edible natural pigments.

Influence of different factors on the stability of rosemarin pigments

1. The effect of light on the stability of rosemarin pigments

In measuring the effect of light on pigment stability of rosehips, two ways of comparison were used: avoiding light and light exposure.

As can be seen from Fig. 1, under light conditions, the longer the placement time, the absorbance decreased significantly, accompanied by a clear trend change, indicating that light has a greater impact on the stability of rosemarsh pigmentation, should be stored away from light; while the longer the placement time, the longer the absorbance has a tendency to decrease, but the change is not significant, indicating that storage away from light on the stability of rosemarsh pigmentation has a very small impact.

However, no matter in the light or under the condition of light protection, the absorbance has a tendency to decrease, so the rosehip pigment should not be placed for too long, and should be used now and stored under light protection as far as possible.

2. Effect of temperature on the stability of rosehips pigments

As can be seen from Figure 2, along with the gradual increase in temperature, the absorbance of the extract gradually decreases, and the trend is obvious, which indicates that the thermal stability of rosehip pigment is not good, and its structure is easily destroyed under high temperature conditions, so it is better to store it under low temperature conditions.

3. The effect of food acidifier (citric acid) on the stability of rosehips pigments

Citric acid is an important food acidifier, which is widely used in the food industry. It is odorless, has a strong sour taste, and is easily soluble in water, making it one of the acidifiers with the largest dosage in the food industry.

In the process of practical application, we often encounter the production of food products such as beverages with citric acid as acidulant and rosmarinic acid pigment as colorant, so it is of practical significance to determine the effect of citric acid on the stability of rosmarinic acid pigment by using citric acid as the research material. The effect of citric acid mass fraction on the stability of rosehip pigment is shown in Fig. 3.

As can be seen from Fig. 3, with the increase of citric acid mass fraction, the absorbance of the sample solution gradually increased, and the change was obvious, but in practical application, the citric acid mass fraction should be added according to the needs of the product in the right amount, especially in the production of beverages to control the appropriate sugar-acid ratio.

4. Influence of food sweeteners (xylitol) on the stability of rosehips pigments

Xylitol is a natural, healthy food sweetener, its sweetness is comparable to sucrose, dissolved in water can absorb a lot of heat, is the largest of all sugar alcohol sweeteners in the value of heat absorption of a kind, as a substitute for sugar in recent years in the food industry is very widely used.

Similarly, in the process of food industry production and practical application, rosehip pigment extracts as cold drinks or beverages or as other food additives, the actual application of the process of frequent contact with some sweeteners, so xylitol as a research material, to determine the effect of xylitol on the stability of rosehip pigment. The effect of xylitol mass fraction on the stability of rosmarinic pigment is shown in Fig. 4.

As can be seen from Fig. 4, with the increase of xylitol mass fraction, the absorbance of the sample solution firstly increased and then decreased, and the change was obvious, and in the practical application, the xylitol mass fraction of about 6% was more suitable.

5. Influence of salt on the stability of pigmentation of rosehips

As can be seen from Figure 5, with the gradual increase in the mass fraction of salt, the absorbance of the sample solution rose slightly, but the change was small, so in the actual application process, according to the specific needs of the product can be basically ignored the impact of its pigmentation of rosmarinus officinalis.

6. The influence of common metal ions on the stability of rosehips pigments

Through the test phenomenon, it was found that the color of the solution with the addition of Fe2+, Al3+ and Cu2+ changed to purple-black, bright purple and dark purple respectively. This indicates that contact with iron, aluminum, copper containers and ionic solutions should be avoided during the application, preservation and use of rosehips pigments;

The color of the sample solution with K+, Ca2+ and Zn2+ did not change significantly. The absorbance of the sample solutions with K+, Ca2+ and Zn2+ was measured at the maximum absorption wavelength, and the results were 0.547, 0.562 and 0.555, respectively, which showed that the absorbance of the sample solution with Ca2+ became larger, the absorbance of the sample solution with K+ became smaller, and the absorbance of the sample solution with Zn2+ remained basically unchanged. Therefore, the effect of these three ions can be neglected in the normal application of rose bengal pigment.

Conclusion

(1) Rosemarie pigment has poor light resistance and should be stored away from light when stored. The thermal stability of rosemarin pigment is poor, and its structure is easily destroyed under high temperature conditions, so it is better to store it under low temperature conditions.

(2) Citric acid mass fraction makes the absorbance of the sample solution gradually increase, the influence is obvious, in the practical application, citric acid mass fraction should be added according to the demand of the product in an appropriate amount.

(3) Xylitol mass fraction makes the absorbance of the sample solution rise first and then fall, the effect is obvious, in practical application, xylitol mass fraction of about 6% is more appropriate.

(4) Table salt mass fraction has little effect on the stability of rose pigment, according to the specific needs of the product can be ignored its effect on the rose pigment.

(5) Different kinds of metal ions have different effects on the stability of rosehip pigment, Fe2+, Al3+, Cu2+ 3 kinds of metal ions have a greater effect on rosehip pigment, while K+, Ca2+, Zn2+ 3 kinds of metal ions have basically no effect.