The processing method of Beetroot Juice Powder significantly affects the antioxidant activity and bioavailability of the phytochemicals it contains. Vacuum-microwave drying, fermentation and irradiation of beetroot enhanced its antioxidant capacity and pigment stability. And hot air drying reduces its color retention. Factors that affect the stability of antioxidants or betalain pigments during processing and storage include pH, temperature, light, water activity, oxygen, metals, etc.
Factors that Affect Beetroot Powder
1. pH Value
The pH value is 3-7, the betanin pigment has the best stability. This suggests that beetroot is best added to acidic foods in different food formulations. When the pH value was 5, the betanin pigment was more stable in the extract. However, when the pH value is below 3, the color of betanin pigment tends to be purple. When the pH value is above 7, the color of betanin pigment tends to be blue. At the same time, under fluorescent conditions, the degradation rate of betanin pigment was three times higher than that at pH 3.
The results show that under aerobic conditions, betanin pigments are relatively stable at pH values between 5.5 and 5.8. Under anaerobic conditions, betanin pigments are relatively stable at pH 4-5.
2. Water activity
Water activity affects the stability of betalain pigments by controlling the water-dependent hydrolysis reaction of aldimine bonds. During different treatments such as spray drying and concentration, the water activity decreased (below 0.63), which improved the stability of betalain pigments. When the water activity was increased from 0.32 to 0.75, the degradation rate of betanin pigments increased significantly. It can be seen that the fluctuation of water activity has a great influence on the stability of betanin pigment, which provides a favorable theoretical basis for the food processing industry using beetroot as raw material.
3. Temperature
Thermal processing is often used to produce different processed products. Temperature affects the stability of betanin pigments. Elevated temperature leads to the degradation of betalain pigments and the inactivation of polyphenol oxidase. However, thermal degradation is also affected by temperature range, degree of heating, presence of oxygen and pigment concentration. Therefore, in the processing of beetroot, temperature is an important factor affecting the quality of the food.
4. Lighting
Under light conditions, pigments are oxidized and degraded. There is an inverse relationship between the light intensity in the range of 2200-4400lux and the stability of betanin pigments.
In the ultraviolet and visible light range, the electrons of the betaine pigment chromophore are placed in a high-energy state, triggering higher reactivity or lower activation energies of the molecule. However, the light effect is negligible under anaerobic conditions. During the storage and processing of beetroot, attention should be paid to light's influence to avoid light accelerating the oxidative degradation of betanin pigments.
5. Metal
Some metal cations, such as iron, copper, tin, and aluminum, have accelerated the degradation of betalain pigments. Early studies have shown that beetroot juice is less sensitive to metal ions in the presence of metal complexing agents. It has been reported that chelating agents (citric acid and EDTA) can enhance the stability of betalain pigments and resist the catalytic degradation of metals. The results of this study provide theoretical guidance for the use of betalain pigments as food additives, and avoid the problem of product discoloration caused by the presence of metal ions.
Summary
The influence of the above factors provides a sufficient theoretical basis for applying beetroot in food processing. This avoids degrading processed beetroot foods' quality due to improper handling, high temperature, low or high pH, high water activity, etc. At the same time, by analyzing these reasons, the quality of food can be improved to meet the different needs of consumers.