The Study On The Improving Approaches Of Color Rendering Effect Of Aluminum-free Carminic Colorant

As a natural anthraquinone colorant,carminic acid has bright color,good light and heat stability,and great application potential for the dyeing of food,medicine,and cosmetics.However,the color of carminic acid is susceptible to the environment?such as pH and metal ions,etc.?,which limits its application in food.The carminic aluminum lake with a relatively stable color is commonly used for dyeing in business,but the safety of its application in food is questioned due to the presence of aluminum in the molecule.At present,there are few studies on the cause of the color change of carminic acid at home and abroad.The only small amount of literatures still have some contradictions,and it is difficult to support the development of carminic aluminum-free colorant and its application in food.Based on these,with the goal of developing aluminum-free carminic colorant,the color of carminic acid and carminic aluminum lake in different food substrates was discussed,the effects of different ingredients on the color of carminic colorant were clarified,and the mechanism of the stable color of aluminum lake was clarified.In order to promote the wide application of carminic acid in food,considering the stabilization mechanism of aluminum lake,using two ways of chelating metal ions,protecting and improving carminic acid and its environment,the improving of the amphoteric compounds,metal chelating agents,and protein-polyphenol-carminic acid complexes on the color of carminic acid were investigated.Firstly,the color of carminic acid and carminic aluminum lake in different foodstuffs?surimi,fish fillet,pork minced meat,chicken minced meat,milk,cream,and soybean milk?was investigated.The results showed that the color of carminic acid in different foodstuffs was quite different:surimi and fish fillet were purple;pork minced meat,chicken minced meat and soybean milk were dark red;milk and cream were gray-green.In comparison,the color of carminic aluminum lake was relatively stable.Except for surimi and pork minced meat,other foodstuffs were all pink.In order to explore the factors that may cause the color of the carminic colorant to be unstable,the effects of common proteins?myofibrillar protein?MFP?,whey protein isolate?WPI?,soy protein isolate?SPI?,and casein?,metal ions(Fe³⁺,Fe²⁺,Ca²⁺,and Cu²⁺),and food additives?sodium nitrite,ascorbic acid,and monascus color?on the color of carminic acid and carminic aluminum lake were investigated.The results showed that 5.38 mg/m L MFP,1%WPI,1%SPI and 1%casein changed the color of carminic acid to wine red,wine red,wine red and orange by increasing the pH of the solution.The color of carminic aluminum lake was pink,which was not affected by protein.By the chelation with 1 mmol/L Fe³⁺,1 mmol/L Fe²⁺,100mmol/L Ca²⁺and 1 mmol/L Cu²⁺,the color of carminic acid was changed to black,brown,brown and purple,respectively.Fe³⁺,Fe²⁺and Cu²⁺can change the color of carminic aluminum lake.However,Ca²⁺had no effect on the color of carminic aluminum lake.Carminic acid can be oxidized by 0.01%sodium nitrite in an acidic environment,and the color can be changed to yellow.The color of carminic aluminum lake also can be changed by the oxidation of sodium nitrite.But 0.01%-1%ascorbic acid and 0.01%-0.1%monascus color did not significantly affect the molecular structure of either carminic acid or carminic aluminum lake.The above results indicated that the pH of materials,metal ions and oxidants that damage the structure can significantly affect the color of carminic acid.The color of carminic acid in the food system may be improved,by adding amphoteric compounds,chelating metal ions or protecting the structure of carminic acid and improving its environment.In order to improve the color of carminic acid in iron-containing and calcium-containing food system?such as meat products and dairy products?and make it present a bright red tone in food,based on the way of adding amphoteric compounds and chelating metal ions to improve the color of carminic acid,the effects of Al³⁺,Zn²⁺,glycine,glutamic acid glutathione,casein phosphopeptide,WPI and ethylenediaminetetraacetic acid?EDTA?on the color of carminic acid in iron-containing and calcium-containing solution were investigated.The results showed that Al³⁺had no obvious improvement on the color of the solution containing 1 mmol/L Fe³⁺,but Al³⁺can prevent the color of carminic acid from being affected by 1-100 mmol/L Ca²⁺.It illustrated that the order of Fe³⁺,Al³⁺and Ca²⁺chelating ability with carminic acid is Fe³⁺>Al³⁺>Ca²⁺.Zn²⁺can chelate with carminic acid to make it purple.Zn²⁺had no obvious improvement on the color of the carminic acid solution containing 1 mmol/L Fe³⁺and 100mmol/L Ca²⁺.It illustrated that the order of Fe³⁺,Zn²⁺and Ca²⁺chelating ability with carminic acid is Fe³⁺>Zn²⁺>Ca²⁺.Glutamic acid and glutathione can change the color of carminic acid in aqueous solution containing 100 mmol/L Ca²⁺to orange by the chelation with Ca²⁺,and no brown floc was formed.EDTA had a strong chelating ability with Fe³⁺and Ca²⁺,and can improve the color of carminic acid solution containing 1 mmol/L Fe³⁺and 100 mmol/L Ca²⁺.The above studies confirmed that acidic amphoteric compounds and metal chelating agents have a certain effect on improving the color of carminic acid in iron-containing and calcium-containing solutions,and balancing pH and chelating Fe³⁺and Ca²⁺are effective ways to improve the color of carminic acid.According to the above results,based on the goal of developing aluminum-free carminic colorant,from the perspective of protecting the structure of carminic acid and improving its environment to improve the color of carminic acid,five WPI-tannic acid-carminic acid complexes?complex without metal ion,complex containing KCl,complex containing CaCl₂,complex containing MgCl₂,and complex containing ZnCl₂?were prepared,the color value,light stability and thermal stability of the complexes were tested,the color and force of the complexes in iron-containing and calcium-containing were studied,and the color of minced meat and cream after being dyed by five complexes was investigated.The results showed that after the complex was placed under the conditions of light,4°C,25°C,37°C and 60°C for 14 d,the color of the complex did not change significantly;after being placed at 80°C for 14 d,the color of the complex became darker.The color value of the complex was 10.25,which was about 1/17 of the color value of carminic acid.The five complexes can significantly improve the color of carminic acid in alkaline solution containing Fe³⁺or Ca²⁺.In pH 8.0 buffer,when the concentration of Fe³⁺was 1 mmol/L,the five complexes appeared amaranth;when the concentration of Ca²⁺was 100 mmol/L,the four complexes containing K⁺,Ca²⁺,Mg²⁺,and Zn²⁺appeared magenta.The addition of urea,sodium dodecyl sulfate and dithiothreitol did not significantly change the color of the complexes in alkaline iron-containing and calcium-containing solution,indicating that there may be covalent interactions between WPI,tannic acid,carminic acid and metal ions.The five complexes were magenta in cream,so the color was significantly improved compared to carminic acid.The above studies have confirmed that protecting carminic acid and improving the environment of carminic acid can effectively improve the color of the complexes in calcium-containing food systems;protein-polyphenol-carminic acid complex as an aluminum-free pigment can be widely used in dairy systems in the future.