Purple cowpea is called purple cowpea, which is a variety of normal cowpea, but the color is different, and 80% of the nutrients are the same, and there is no difference. Commonly known as beans, ginger beans, beans, hanging beans. Purple cowpea is divided into long cowpea and rice cowpea, belonging to leguminous plants. Purple cowpea is an annual plant in Leguminosae. There are three kinds of stems: dwarf, semi-tendril and tendril. The cultivation in South China is dominated by vines, followed by dwarf plants. Cowpea can be divided into green and white by color. Mung beans are younger and harder, and white beans are thicker and worse. Purple cowpea is a common vegetable that people eat and can also be used as medicine. The flowering and fruiting period is from June to September.

Purple cowpea is a normal cowpea, but its color is different. 80% of the nutrients are the same as common cowpea, which can be divided into cowpea and rice cowpea, and can also be used as medicine.

Cowpea sowing can be divided into direct seeding and seedling transplanting. The main roots of direct seeding are deep and the stems and leaves are lush. If the management is careless, it is easy to grow in vain, which will affect the flowering and pod setting and reduce the yield. Seedling transplanting can inhibit vegetative growth, promote flowering and pod setting, and cultivate cowpea in spring. In order to catch up early and prevent seed rot and seedling death in early spring, seedlings can be raised in nutrient bowls or flat plastic film arches. The seedling age is 20-25 days. We should strengthen seedbed management and pay attention to exercise at seedling stage. Seedbed seedlings are generally transplanted and planted before the first compound leaves grow. Seedling raising in nutrition bowl can be delayed to grow 2 ~ 3 compound leaves, and can be planted in sunny days.

Cowpea has a wide adaptability to soil, can be planted on the land with good drainage and loose soil, and grows well at pH 6.2 ~ 7. Plantar fertilizer should be applied before planting, and soil should be carefully prepared. Dig deep into the land before winter, leave stubble for winter, and apply about 3000 ~ 5000 kg of decomposed organic fertilizer, 25 ~ 50 kg of calcium superphosphate, 25 kg of potassium fertilizer or 30 kg of NPK compound fertilizer per mu in spring. After several shallow turns and raking, the boundary of 1.3m is formed. The general planting density is 60 cm row spacing and 27-33 cm plant spacing. Planting density can be appropriately adjusted according to different varieties and different soil fertility conditions.

Taking cowpea as raw material, the physical and chemical properties of cowpea pigment in pods and seeds and the effects of preservatives, pH value, light, temperature, reducing agent, oxidant and seven common metal ions on its stability were studied, so as to provide theoretical basis for the extraction, processing and industrial application of cowpea pigment. The results showed that the maximum absorption wavelengths of the purple pigment from pod and seed were 270nm and 207nm in ultraviolet region and 542nm and 48 1nm in visible region, respectively. Purple pigment has good water solubility, and its color changes with pH value. When the pH value is 7, the color changes from purple to green. The pigment has good stability to light and low temperature under acidic conditions, and has strong oxidation resistance and reduction resistance. Ca2+, Na+, Mg2+, K+ and Zn2+ have little effect on the stability of purplish red pigment, while Cu2+ and Fe3+ ions make the stability of the pigment worse.