Determination of Prebiotic Components, In Vitro Starch Digestibility, and Glycemic Index of Taiwanese Jicama Tubers(Pachyrhizus erosus (L.) Urban)

• Main Authors: Alvaro David Lopez Martinez, 艾瓦洛
• Other Authors: Albert Linton Charles
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/j7z86p

碩士 === 國立屏東科技大學 === 熱帶農業暨國際合作系 === 105 === Pachyrhizus erosus (L.) Urban is a plant from the Leguminosae family that develops a widely available tuberous root crop also known as jicama or doushu in Taiwan. In the tropical and subtropical regions of Asia and America, the tubers are used as a cheap source of carbohydrates for livestock and human nutrition. In the other hand, the plant tissues above ground are known for its high concentration of a toxic compound called rotenone, sometimes used as an effective pesticide and piscicide. Although jicama is widely available, it has been underutilized and very little research has been done in order to reveal its functional properties. Nevertheless, it has been reported to have a high nutritious profile, rich in vitamins (ascorbic acid, thiamine, riboflavin, pyridoxine and niacin), minerals (potassium, sodium, phosphorus, calcium and magnesium), carbohydrates, and fibrous compounds. In Taiwan, jicama is popularly used in the local cuisine as a vegetable that enhances food flavor and texture, as the tuber remains crispy and preserves its physical characteristics even after being cooked. The large rounded heart-shaped tuber fairly beige colored is the most commercial variety; however, a smaller biotype with a slighter irregular shape can also be available seasonally. The objectives of this study were to develop an efficient way to extract flour and starch from jicama tuberous root crop, in order to determine the probiotic compounds by means of inulin content expressed in fructose concentration in the fresh root crop and the flour extracted from jicama. Furthermore, it was intended to conduct an in vitro starch digestibility analysis to identify the starch profile and quantify the amounts of resistant starch, slowly digestible starch, and rapidly digestible starch present in jicama’s fresh tubers and flours, and to determine the Hydrolysis Index and Glycemic Response of the local biotypes. The samples were also analyzed for their proximate physico-chemical composition. Fresh jicama samples presented higher moisture content, of 90 to 94 %, when compared with other traditionally consumed root tuberous crops (potato and sweet potato). Similarly, jicama exhibited appreciable amounts of carbohydrates in fresh samples (14.90 %) and from flours extracted from the tubers (8.63 %). This study determined that jicama samples contain higher amount of hexoses (165.17 g/L) in relation to pentoses (98.75 g/L), additionally inulin content based on the concentration of fructose present in jicama was among the parameters of other root crops, in both fresh tubers (8.94 %) and flour (12.30 %). This suggests the potential for being used in mitigating symptoms developed from health problems such as morbid obesity or Binge eating disorder. On the other hand, when analyzing starch digestibility, it presented a less favorable profile indicating freshly made flour (1 - 6 months old) with a higher glycemic response (GI 91) and a hydrolysis index (HI 93.39) when compared to an aged jicama flour (6- 18 months old) where the glycemic response (GI 78) and the hydrolysis index (HI 69.19) were beneath the standards when compared to a reference food such as white bread (HI 100 and GI 100). Furthermore, jicama processed flours can be an alternative food source of gluten-free starch for people with digestive disorders such as celiac disease patients, and while flours might not be recommended for people with low glucose response diet requirements, such as diabetic patients, the low glycemic response (GI 60) and hydrolysis index (HI 37.41) in fresh tubers may be more suitable for patients with such conditions. This study confirmed that in Taiwanese Pachyrhizus erosus (L.) Urban tuberous root crop possessed functional food properties that could benefit people with specific dietary requirements and medical conditions. Moreover, its high moisture content and availability to be eaten as a fruit in its raw stage provides a direct and accessible form of nutritious low calorific value food that can be utilized for developing diets to benefit people with weight management problems or low glucose tolerance. It is advisable that the food industry takes in consideration this underutilized crop when formulating food supplements and diets with such requirements.