Anthocyanins are widely distributed compounds in nature that serve a dual purpose: they produce a wide array of vibrant colors and they possess potent antioxidant properties. The ability to harvest the natural rich colors of anthocyanins as a potential replacement for synthetic dyes such as FD&C Red No. 40 will fulfill the modern consumer’s demand for a more natural and healthful product. Anthocyanins present in red radish skins provide color intensity, under acidic conditions, similar to that of FD&C Red No. 40 and could provide a useful tool for the food industry. Additionally, radish anthocyanins exhibit higher stability than most other anthocyanin extracts.
The objective of this work was to harvest an anthocyanin-rich natural colorant from cull radishes, a waste product, in order to produce a high quality product free of undesirable aromas that provides color and added value suitable for food applications.
From cull or premium radish skins, the color was extracted by abrasive action or steam to produce a colored juice. Filtration, evaporation, salt and acid addition and heat were evaluated as means of removing undesirable aromas and flavors or minimize their formation during processing. Samples were analyzed using UV-vis spectroscopy, HPLC and sensory analyses.
Premium and cull radishes produced very similar products. A chemical extraction of red radish skins yielded 107mg pelargonidin-3-glucoside equivalents (pg-3-glu eq)/100g of skin. Abrasive peeler effectively extracted pigments from cull radishes, salt and acid significantly decreased aroma formation, but created the new challenge of salt removal. Nano-filtration reduced the anthocyanin yield from 83.6mg/100g skin to 72.6mg pg-3-glu eq/100g of skin. Concentration of the juice in a rotary evaporator for 1-10 min helped decrease aroma intensity and produced a juice with 224-206mg pg-3-glu equivalents/L. Steam was effective at safely removing between 25-50% of the anthocyanins from the skins while preventing aroma and flavor formation.
A sensory panel found the quality of color to be comparable to FD&C Red No. 40, and found that samples extracted with salt, acid or steam had lower aroma intensity.
Despite the lower pigment yields, the steam extraction method was preferred because of its simplicity, and quality of the final product. Additionally, the product being created is from a waste material naturally generated by the radish company. This waste can be turned into a high quality food colorant. Using this resource potentially increases the sustainability of a product and the land by making the end product more cost effective for the business, while providing consumers with a healthy alternative to synthetic dyes.