Roshani Shakya

Tuber-specific silencing of the acid invertase gene substantially lowers the acrylamide-forming potential of potato.

Some popular processed foods including French fries contain small amounts of toxic acrylamide. Efforts to lower the accumulation of this reactive compound by modifying the production process have a negative effect on sensory characteristics and are not broadly applicable. This study optimized a method developed more than a decade ago to lower the accumulation of the acrylamide precursors glucose and fructose in cold-stored tubers. In contrast to the original application, which lowered hexose content by one-third through constitutive expression of an antisense copy of the cold-inducible acid invertase (Inv) gene, the current approach was based on tuber-specific expression of an Inv-derived inverted repeat. Stored tubers of transgenic plants contained as little as 2% of the reducing sugars that accumulated in controls. This decline in glucose and fructose formation is counterbalanced by increased sucrose and starch levels. However, it did not trigger any phenotypic changes and also did not affect the formation of free asparagine, ascorbic acid, phenylalanine, and chlorogenic acid. Importantly, French fries from the low-invertase tubers contained up to 8-fold reduced amounts of acrylamide. Given the important role of processed potato products in the modern Western diet, a replacement of current varieties with the low-hexose potatoes would reduce the average daily intake of acrylamide by one-fourth.

LC-MS Analysis of Solanidane Glycoalkaloid Diversity among Tubers of Four Wild Potato Species and Three Cultivars (Solanum tuberosum)

Secondary metabolites in potato tubers include both phytonutrients and plant defense compounds. The extent these small molecules vary among different potato genotypes is not well characterized. LC-MS analysis of tuber extracts from seven potato genotypes showed that one large source of small molecule variation is the glycoalkaloids. Glycoalkaloids are involved in the resistance of potatoes to pathogens and pests, but they also have implications for human health and nutrition. This study focused on glycoalkaloids with solanidane or solanidane-like aglycones, of which over 50 were tentatively identified, many of which appeared to be novel glycoalkaloids. Results suggested the variety of glycoalkaloids in potatoes is considerably greater than previously thought. Dissecting the role of these many glycoalkaloids in human health or pest and pathogen resistance will be a formidable undertaking.

Nutritional Value of Potatoes: Vitamin, Phytonutrient, and Mineral Content

Publisher Summary Potatoes are the fourth most grown crop in the world, after the cereals rice, wheat, and maize, and are the only major food crop that is a tuber. Potatoes are a good source of many vitamins and minerals; if one compares percentage of recommended daily allowance (RDA) of calories in a given portion size versus the percentage of the RDA of vitamins and minerals in that same portion, many vitamins and minerals exceed the percentage of calories. Potatoes are a well-known source of vitamin C, with a medium red-skinned potato (173 grams) providing about 36% of the RDA according to the USDA databases. Vitamin C has a major role in detoxifying reactive oxygen species in plants, which are the primary source of vitamin C in the human diet.Publisher Summary Potatoes are the fourth most grown crop in the world, after the cereals rice, wheat, and maize, and are the only major food crop that is a tuber. Potatoes are a good source of many vitamins and minerals; if one compares percentage of recommended daily allowance (RDA) of calories in a given portion size versus the percentage of the RDA of vitamins and minerals in that same portion, many vitamins and minerals exceed the percentage of calories. Potatoes are a well-known source of vitamin C, with a medium red-skinned potato (173 grams) providing about 36% of the RDA according to the USDA databases. Vitamin C has a major role in detoxifying reactive oxygen species in plants, which are the primary source of vitamin C in the human diet.

Synthesis and regulation of chlorogenic acid in potato: Rerouting phenylpropanoid flux in HQT-silenced lines.

Chlorogenic acid (CGA) is the major phenolic sink in potato tubers and can constitute over 90% of total phenylpropanoids. The regulation of CGA biosynthesis in potato and the role of the CGA biosynthetic gene hydroxycinnamoyl CoA:quinate hydroxycinnamoyl transferase (HQT) was characterized. A sucrose induced accumulation of CGA correlated with the increased expression of phenylalanine ammonia-lyase (PAL) rather than HQT. Transient expression of the potato MYB transcription factor StAN1 (anthocyanin 1) in tobacco increased CGA. RNAi suppression of HQT resulted in over a 90% reduction in CGA and resulted in early flowering. The reduction in total phenolics and antioxidant capacity was less than the reduction in CGA, suggesting flux was rerouted into other phenylpropanoids. Network analysis showed distinct patterns in different organs, with anthocyanins and phenolic acids showing negative correlations in leaves and flowers and positive in tubers. Some flavonols increased in flowers, but not in leaves or tubers. Anthocyanins increased in flowers and showed a trend to increase in leaves, but not tubers. HQT suppression increased biosynthesis of caffeoyl polyamines, some of which are not previously reported in potato. Decreased PAL expression and enzyme activity was observed in HQT suppressed lines, suggesting the existence of a regulatory loop between CGA and PAL. Electrophysiology detected no effect of CGA suppression on potato psyllid feeding. Collectively, this research showed that CGA in potatoes is synthesized through HQT and HQT suppression altered phenotype and redirected phenylpropanoid flux.

Tastier and healthier alternatives to French fries.

The effect of both the origin and shape of potato cuts on fry quality was investigated in this study. Linear strips from the inner core of tubers were compared to those from outer tissues, both before and after processing, and strips from either specific tissues or whole peeled tubers were also evaluated against ring-shaped cuts. Both strips and rings had 0.7 cm sides and, in most cases, a volume of 4.9 cm(3). They were analyzed for moisture content, antioxidants, asparagine, and reducing sugars. The material was then blanched, dipped in 0.5% disodium acid pyrophosphate and 0.3% glucose, dried at 77 degrees C, par-fried in soybean oil at 191 degrees C, and finish-fried at 168 degrees C. The fried product was analyzed for sensory characteristics and oil, salt, and acrylamide content. Our results showed that strips from the inner core absorbed 28% more oil and exhibited inferior sensory characteristics compared to strips from the outer parts. The extended drying and frying times needed to match the crispness and flavor of inner strips to those of regularly fried outer strips resulted in a further increased absorption of oil and, importantly, triggered a 163% increase in levels of the toxic Maillard reaction product acrylamide. Potato rings consisted of higher dry matter material, contained more antioxidants, and had a lower surface-to-volume ratio than the conventional linear strips. Upon processing, they also absorbed 22% less oil, contained 26% less salt, and displayed superior sensory properties. Thus, ring fries may represent an attractive alternative to French fries as processed staple food.

Vitamins, Phytonutrients, and Minerals in Potato

Potatoes contain a complex mix of phytonutrients in amounts that vary greatly among cultivars and primitive germplasm. Potatoes contain sizable amounts of vitamin C and potassium, the two phytonutrients for which they may be best known. Potatoes also contain important amounts of other phytonutrients, including protein, fiber, complex carbohydrates, carotenoids, and B vitamins, and are one of the primary suppliers of polyphenols to the diet. Red- and purple-fleshed potatoes can provide especially high amounts of phenylpropanoids including chlorogenic acid and anthocyanins. Immature tubers contain higher amounts of many phytonutrients than at maturity and are marketed typically as “new” or “baby” potatoes. Tubers also contain glycoalkaloids that can have undesirable effects if present at too high a concentration, although research over the past decade has increasingly shown a range of potential health-promoting properties for these compounds, including anticancer effects. Potatoes provide more calories per acre than any other major crop and have historically played an important role in providing food security. With forecasts that global food production must double by 2050, potatoes will continue to have a key role, especially in Asia and Africa, where production of potatoes has markedly increased in recent decades. While this staple food is already an important source of phytonutrients, genomics and metabolomics, along with the elucidation of phytonutrient biosynthetic pathways and regulatory mechanisms, allow new approaches to be undertaken by traditional and molecular breeders to further increase the phytonutrient content of potato.

Chapter 14 – Nutritional Value of Potatoes: Vitamin, Phytonutrient, and Mineral Content

Publisher Summary Potatoes are the fourth most grown crop in the world, after the cereals rice, wheat, and maize, and are the only major food crop that is a tuber. Potatoes are a good source of many vitamins and minerals; if one compares percentage of recommended daily allowance (RDA) of calories in a given portion size versus the percentage of the RDA of vitamins and minerals in that same portion, many vitamins and minerals exceed the percentage of calories. Potatoes are a well-known source of vitamin C, with a medium red-skinned potato (173 grams) providing about 36% of the RDA according to the USDA databases. Vitamin C has a major role in detoxifying reactive oxygen species in plants, which are the primary source of vitamin C in the human diet.Publisher Summary Potatoes are the fourth most grown crop in the world, after the cereals rice, wheat, and maize, and are the only major food crop that is a tuber. Potatoes are a good source of many vitamins and minerals; if one compares percentage of recommended daily allowance (RDA) of calories in a given portion size versus the percentage of the RDA of vitamins and minerals in that same portion, many vitamins and minerals exceed the percentage of calories. Potatoes are a well-known source of vitamin C, with a medium red-skinned potato (173 grams) providing about 36% of the RDA according to the USDA databases. Vitamin C has a major role in detoxifying reactive oxygen species in plants, which are the primary source of vitamin C in the human diet.

Nutritional Value of Potatoes

Publisher Summary Potatoes are the fourth most grown crop in the world, after the cereals rice, wheat, and maize, and are the only major food crop that is a tuber. Potatoes are a good source of many vitamins and minerals; if one compares percentage of recommended daily allowance (RDA) of calories in a given portion size versus the percentage of the RDA of vitamins and minerals in that same portion, many vitamins and minerals exceed the percentage of calories. Potatoes are a well-known source of vitamin C, with a medium red-skinned potato (173 grams) providing about 36% of the RDA according to the USDA databases. Vitamin C has a major role in detoxifying reactive oxygen species in plants, which are the primary source of vitamin C in the human diet.Publisher Summary Potatoes are the fourth most grown crop in the world, after the cereals rice, wheat, and maize, and are the only major food crop that is a tuber. Potatoes are a good source of many vitamins and minerals; if one compares percentage of recommended daily allowance (RDA) of calories in a given portion size versus the percentage of the RDA of vitamins and minerals in that same portion, many vitamins and minerals exceed the percentage of calories. Potatoes are a well-known source of vitamin C, with a medium red-skinned potato (173 grams) providing about 36% of the RDA according to the USDA databases. Vitamin C has a major role in detoxifying reactive oxygen species in plants, which are the primary source of vitamin C in the human diet.