Chlorophyll and its derivatives are not only excellent colorants, but also have a series of functional characteristics. The chelating stability of porphyrin ring of chlorophyll with magnesium ion is not good. Copper or zinc can be used instead of magnesium, which can not only enhance the stability of pigment, but also have good water solubility. Sodium copper chlorophyllin can be used for food coloring and has antipyretic and hemostatic effects.
Monascus pigment is mainly produced in Fujian, Zhejiang, Guangdong and other places in China, and is generally used for wine making and ham sausage coloring. If Monascus contains a certain concentration of Monacolin K, which is a functional component that can inhibit cholesterol, it is called functional Monascus. It is reported that the United States has begun to import functional monascus from China as a food supplement to the market; Europe imported monascus from China as a food ingredient for ham sausage production. Therefore, China's monascus, including monascus rice and monascus rice flour products, has shown excellent market prospects.
However, compared with synthetic pigments, natural pigments are not satisfactory in many aspects, especially sensitive to light, heat and pH value, and sensitive to oxidation, reduction and microbial action. How to overcome the problems of fading and discoloration caused by this is an important topic in the study of natural pigments.
Carotenoids are greatly influenced by water, light and temperature, mainly manifested as oxidative metamorphism and non-oxidative metamorphism. Oxidative metamorphism can be divided into non-enzymatic oxidation (composite oxidation, metal ion catalytic oxidation and pure oxygen oxidation) and enzymatic oxidation (lipoxygenase oxidation, lipoperoxidase oxidation and peroxidase oxidation). But will not be oxidized and deteriorated; Cis-trans isomerization, isomerization of epoxy compounds.
For example, the yellow pigment molecule with vitamin A activity in β -carotene has many unsaturated double bonds, which are sensitive to light, oxygen and heat and easy to degrade; Gardenia yellow is a rare water-soluble carotenoid in nature, which has good dyeability to food, but poor light resistance and heat resistance, and will turn green when used in food. Anthocyanin pigment is extremely unstable, and it will fade and brown under the influence of acidity, heating, oxidation, reduction, sugar, light, metal ions and ascorbic acid during processing and storage.
In addition, deoxyascorbic acid and hydrogen peroxide produced by natural oxidation of ascorbic acid also have great influence on the fading and discoloration of anthocyanins. For example, the pigment extracted from grape skin is water-soluble, red when acidic, blue when neutral and alkaline, unstable to heat and light, and can be discolored by metal ions; Monascus is easy to dye protein, but it has poor light resistance and will fade under fluorescent light. The light resistance and heat resistance of beet red are poor. Under the condition of 100℃, its red color gradually turns to light yellow and brown, and oxidation can also make it fade or brown.