Therefore, it is the ideal material for the production of fermented food products. Besides, purple sweet potato also contains anthocyanins relatively large about 51,5-174,7mg / 100g of material.

Anthocyanins from purple sweet potatoes in addition to creating beautiful colors and safe food products, it also proved to be compounds with high biological activity, high oxidation resistance, antibacterial, cancer prevention and etc.

From these characteristics, may notice that the purple sweet potato is an ideal raw material for the fermentation of acetic acid forming beautiful red vinegar food products and having high nutritional value. Therefore, the scientists from Da Nang College of Food implemented the study.

Acetic acid fermentation from purple sweet potato was conducted on three ethanol fermentation specimens with concentration of 2%, 4% and 6%. The study results showed that the sample of purple yam 4% of ethanol concentration was suitable for acid fermentation than ethanol sample with 2% and 6% of content.

Also, after fermentation, anthocyanins fastness of 4% sample was higher than 2% and 6% (fastness of 2% sample was 82.38%, fastness of 4% sample was 88.35% and fastness of 6% sample was 79.16%). End of fermentation, fermented content with acetic acid was 29.6 g / l, pH = 2.72, anthocyanins content 3.23 mg / 100ml and the total acid content was 30.39 g / liter.