Value of Extracting Anthocyanins from Purple Sweet Potatoes
Anthocyanins are water-soluble pigments that can change color with the acidity or alkalinity of cellular fluid. The cellular fluid turns red in acidic conditions and blue in alkaline conditions. Anthocyanins are one of the main pigments that constitute the colors of petals and fruits, synthesized through the phenylpropanoid pathway and flavonoid biosynthesis pathways. Factors affecting the coloration of anthocyanins include the structure of anthocyanins, pH value, co-pigmentation effects, etc. The fruit peel's color is influenced by internal, external factors, and cultivation techniques. Light can increase the content of anthocyanins; high temperatures can cause the degradation of anthocyanins. Anthocyanins are secondary metabolites of plants and play an important role physiologically. The colors of petals and fruits currently have relatively mature anthocyanin products on the market. These anthocyanins mainly include bilberry anthocyanins, blueberry anthocyanins, cranberry anthocyanins, elderberry anthocyanins, blackberry anthocyanins, and black soybean skin anthocyanins, with contents of 25% or 40%.
1. Functions of Anthocyanins
In recent years, there has been increasing focus on the potential health benefits of anthocyanins as polyphenols. In the future, this characteristic of anthocyanins may be increasingly applied in functional foods and health supplements. They smooth the skin, suppress inflammation and allergies, and improve joint flexibility. Below are some of the functions of anthocyanins:
- Possess anti-mutagenic functions to reduce the formation of carcinogens;
- Help prevent various diseases associated with free radicals, including cancer, heart disease, premature aging, and arthritis;
- Protect the inner walls of arteries;
- Enhance the immune system's ability to resist carcinogens;
- Reduce the occurrence of heart disease and strokes by preventing stress responses and smoking-induced platelet aggregation;
- Have anti-inflammatory properties, thereby preventing inflammatory conditions such as arthritis and swelling;
- Alleviate pollen allergies and other hypersensitivities;
- Enhance the elasticity of arteries, veins, and capillaries;
- Prevent blood pressure increases caused by the release of angiotensin-converting enzyme from the kidneys (another blood pressure-lowering effect);
- Maintain normal flexibility of blood cells, helping red blood cells pass through tiny capillaries, thus enhancing overall blood circulation, bringing direct benefits to organs and systems throughout the body, and enhancing cell vitality;
- Relax blood vessels to promote blood flow and prevent hypertension (blood pressure-lowering effect);
- Reduce the frequency and duration of colds;
- Act as a barrier to protect brain cells, preventing the formation of beta-amyloid proteins, glutamate toxicity, and free radical attacks, thereby preventing Alzheimer's disease;
- Through the inhibition of elastase and collagenase, make the skin smooth and elastic, preventing skin damage caused by excessive sun exposure both internally and externally.
Anthocyanin pigments are widely found in the tissues of plants such as purple sweet potatoes, grapes, blood oranges, red cabbage, blueberries, eggplant skins, cherries, red oranges, raspberries, strawberries, mulberries, hawthorn skins, perilla leaves, black (red) rice, morning glory flowers, etc.
Anthocyanins bring multiple benefits to the human body. Fundamentally, anthocyanins are powerful antioxidants that can protect the body from damage by harmful substances known as free radicals. Anthocyanins can also enhance vascular elasticity, improve the circulatory system, and enhance skin health, attracting animals for pollination and seed dispersal. Anthocyanins are commonly found in the tissues of flowers and fruits, as well as in the epidermal cells and lower epidermis of stems and leaves. Some fruits determine their market price based on color depth. Anthocyanins belong to the flavonoid class of phenolic compounds. Their basic structure includes two benzene rings connected by a three-carbon unit (C6-C3-C6). Anthocyanins are synthesized through the phenylpropanoid pathway and flavonoid biosynthesis pathway, regulated and catalyzed by many enzymes. The six main non-glycoside forms include pelargonidin, cyanidin, delphinidin, peonidin, petunidin, and malvidin. The color of anthocyanins varies due to factors such as the number of hydroxyl groups (-OH), methylation, glycosylation numbers, sugar types, and connection positions. The color expression changes with biochemical environmental conditions like anthocyanin concentration, co-pigmentation effects, and vacuolar pH values.
There are over 300 different anthocyanins in nature. They come from various fruits and vegetables such as purple sweet potatoes, bilberries, cranberries, blueberries, grapes, elderberries, blackcurrants, purple carrots, and red cabbages, with colors ranging from red to blue. These anthocyanins primarily include delphinidin, cyanidin, petunidin, and pelargonidin.
The color of anthocyanins changes with pH levels, from raspberry red at pH 3 to deep blueberry red at pH 5. In most applications, these pigments exhibit good light, heat, and pH stability and can withstand pasteurization and UHT treatments. Anthocyanins are widely used in beverages, candies, jellies, and jams. The color changes of purple sweet potato anthocyanins at different pH levels are shown in the figure below: Color Changes of Purple Sweet Potato Anthocyanins at Different pH Levels.
2. Research and Application of Anthocyanins
Despite the in-depth research on antibiotics and vitamins, they cannot solve modern diseases such as cardiovascular diseases, diabetes, cancer, sub-health conditions, nor address issues related to longevity and anti-aging. Scientific research shows that if the problem of free radical damage is solved, human cells can truly grow freely, and the average lifespan would certainly reach 125 years. Therefore, human lifespan directly depends on the strength of people's antioxidant and anti-free radical capabilities, and the discovery of anthocyanins provides the simplest and most effective way for people worldwide to combat oxidation and aging.
The discovery and application of anthocyanins have enabled humanity to transition from the antibiotic and vitamin era of the 20th century into the anthocyanin era of the 21st century!
With the development of science and technology, people are paying more attention to the safety of food additives, and the types and quantities of synthetic dyes have significantly decreased. Therefore, developing and applying natural dyes has become the general trend of the world's edible dye industry.