The purpose of this research was the development of the production process of ready-to-eat purple sweet potato soup packaged in retort pouch using varying the amounts of xanthan gum at 3 levels of 0.2, 0.3 and 0.4% of all ingredients and 0% xanthan gum(control). The purple sweet potato soup was packaged in retort pouch of 150g, and steamed at 121^OC for 15 minutes. As the experimental results, this study found that an increase of xanthan gum used in purple sweet potato soup packaged in retort pouches increased the viscosity value with keeping at room temperature for 3 days, which showed no stratification of soup. The result of the sensory evaluation by 9 - Point Hedonic scale showed that 0.4% xanthan gum of purple sweet potato soup in retort pouch had the highest score of appearance, color, taste and overall liking scores than 0.2 and 0.3% xanthan gum, respectively (p≥0.05). The amount of xanthan gum had no significant effects on the color of the purple sweet potato. The study result of the chemical composition of the xanthan gum was primarily used as a thickener, but it was also the most efficient stabilizer for suspensions, emulsions and solid particles in purple sweet potato soup.

The chemical compositions of the purple sweet potato soup packaged in retort pouch found moisture, protein, fat, dietary fiber, ash and carbohydrate, which were 83.63, 0.69, 1.24, 1.94, 1.04 and 13.40% respectively. Total energy was equal to 67.52 kcal/100g, there was the amount of total anthocyanin at 5.83 mg/100g, and total antioxidant activity (DPPH) was equal to 220.26 mgAA/100g. The available data provided in the possibility study of the utilization of purple sweet potato found that it increased antioxidant activity in sweet potato soup. Cost control of standard recipe for ready-to-eat purple sweet potato soup in retort pouch had net weight 150g/bag. Cost control was at 8.05 Bath, actual selling price was 13.00 Bath, and profit was 4.03 Bath.

Keywords: Ready-to-eat, Purple sweet potato, Soup, Retort pouch