Bioactive Compounds in Potato Tubers: Effects of Farming System, Cooking Method, and Flesh Color

Gene expression profiling in Rosa roxburghii fruit and overexpressing RrGGP2 in tobacco and tomato indicates the key control point of AsA biosynthesis

Rosa roxburghii Tratt. is an important commercial horticultural crop endemic to China, which is recognized for its extremely high content of L-ascorbic acid (AsA). To understand the mechanisms underlying AsA overproduction in fruit of R. roxburghii, content levels, accumulation rate, and the expression of genes putatively in the biosynthesis of AsA during fruit development have been characterized. The content of AsA increased with fruit weight during development, and AsA accumulation rate was found to be highest between 60 and 90 days after anthesis (DAA), with approximately 60% of the total amount being accumulated during this period. In vitro incubating analysis of 70DAA fruit flesh tissues confirmed that AsA was synthesized mainly via the L-galactose pathway although L-Gulono-1, 4-lactone was also an effective precursor elevating AsA biosynthesis. Furthermore, in transcript level, AsA content was significantly associated with GDP-L-galactose phosphorylase (RrGGP2) gene expression. Virus-induced RrGGP2 silencing reduced the AsA content in R. roxburghii fruit by 28.9%. Overexpressing RrGGP2 increased AsA content by 8-12-fold in tobacco leaves and 2.33-3.11-fold in tomato fruit, respectively, and it showed enhanced resistance to oxidative stress caused by paraquat in transformed tobacco. These results further justified the importance of RrGGP2 as a major control step to AsA biosynthesis in R. roxburghii fruit.

Biochemical Characterization and Effects of Cooking Methods on Main Phytochemicals of Red and Purple Potato Tubers, a Natural Functional Food

Potato is a staple food crop and an important source of dietary energy. Its tubers contain several essential amino acids, vitamins, minerals and phytochemicals that contribute to the nutritional value of this important product. Recently, scientific interest has focused on purple and red potatoes that, due to the presence of anthocyanins, may be considered as natural powerful functional food. The aim of this study was to evaluate the characteristics of pigmented varieties, the types of anthocyanins accumulated and the level of both beneficial phytochemicals (vitamin C and chlorogenic acids, CGAs) and anti-nutritional compounds (glycoalkaloids) following various cooking methods. The analyses described the presence of a mix of several acylated anthocyanins in pigmented tubers along with high level of CGA. The amount of antioxidants was differently affected by heat treatments according to the type of molecule and the cooking methods used. In some cases, the beneficial compounds were made more available by heat treatments for the analytical detection as compared to raw materials. Data reported here describe both the agronomic properties of these pigmented varieties and the effects of food processing methods on bioactive molecules contained in this natural functional food. They may provide useful information for breeders aiming to develop new varieties that could include desirable agronomical and industrial processing traits.

Effect of Different Methods of Thermal Treatment on Starch and Bioactive Compounds of Potato

The study examined the effects of various methods of thermal treatment of Lord cultivar potato tubers on changes in starch, polyphenols, vitamin C, antioxidant activity, and mineral compounds. Following heat treatment in order to determine further transformations of starch, the potatoes were stored at 2 °C/24 h. Changes in starch, bioactive compounds and antioxidant properties varied depending on the treatment method. In general, higher retention of bioactive compounds was noted for tubers treated with "dry" methods, such as microwaving or grilling than for tubers treated with "wet" methods, e.g., boiling in water, steam cooking or cooking in a combi oven. These samples were also characterised by a higher resistant starch content. Cold storage resulted in an increase in the proportion of resistant starch. Total phenols content ranged from 210.96 (boiling) to 348.46 mg/100 g DW (grilling) and vitamin C content ranged from 43.79 (boiling) to 68.83 mg/100 g DW (microwaving). DPPH radical scavenging activity was the highest for the grilled tubers. The results indicate microwaving and grilling as the most favourable thermal treatments of potato.

Phytochemicals in Leaves and Roots of Selected Kenyan Orange Fleshed Sweet Potato (OFSP) Varieties

This study reports the inherent phytochemical contents in leaves and roots of nine sweet potato varieties from Kenya. Results indicated that vitamin C content varied significantly (P < 0.05) among the sweet potato varieties regardless of the plant part, leaves having significantly (P < 0.05) higher levels than in the roots. Total flavonoids and phenolic compounds differed significantly (P < 0.05) among varieties, higher values were found in leaves than in roots. Flavonoid contents in roots ranged from below detectable limits (Whitesp) to 25.8 mg CE/100 g (SPK031), while in leaves it ranged from 4097 to 7316 mg CE/100 g in SPK4 and Kenspot 5, respectively. Phenolic content was below detectable limits in the roots of whitesp but it was in substantial amounts in orange fleshed varieties. The β-carotene content was significantly (P < 0.05) higher in leaves (16.43-34.47 mg/100 g dry weight) than in roots (not detected-11.1 mg/100 g dry weight). Total and phytic phosphorus were directly correlated with phytate contents in leaves and the roots. Tannins and soluble oxalates varied significantly (P < 0.05) with variety and plant part being higher in leaves. The current information is important for ration formulations and dietary recommendations utilizing sweet potato leaves and roots. Future studies on effects of processing methods on these phytochemicals are recommended.

The Impact of Organic vs. Conventional Agricultural Practices on Selected Quality Features of Eight Potato Cultivars

An organic agricultural system based on natural methods and means of production is an alternative to intensive agriculture. The available research suggests that organic crops, in comparison to the conventional ones, are richer in phenolics and other antioxidants while containing less undesirable pesticide residues and nitrates. The aim of this study was to determine concentrations of polyphenols, lutein, vitamin C, and nitrates in eight potato cultivars (Mazur, Justa, Lawenda, Lech, Tacja, Laskana, Otolia, Magnolia) grown organically and conventionally in a controlled field experiment in Poland. Significant differences between potato tubers of the tested cultivars coming from organic and conventional production were identified for the majority of parameters. Higher concentrations of nitrates and lutein were found in conventional compared to the organic tubers, while organic potatoes were, on average, richer in phenolic compounds. Among the tested cultivars, Magnolia, Otolia, and Laskara were richest in vitamin C and phenolics. Otolia and Laskara also accumulated the highest levels of nitrates. If further confirmed, these observations might be of importance for the producers and consumers, who increasingly search for foods from sustainable and well-controlled agricultural systems.

Antioxidant properties of potato tubers (Solanum tuberosum L.) as a consequence of genetic potential and growing conditions

The concentrations of the bioactive compounds in potato tubers are determined by both genetic potential and environmental factors. The purpose of the experiment was to determine the influence of organic and integrated production on the expression of the genetic potential with respect to the antioxidant properties of potato tubers and to evaluate its stability under different environmental conditions. This phenotyping was performed on seven new breeding lines (tetraploid clones) and three modern cultivars: Jelly, Satina and Tajfun. The results indicated that production system and location significantly influenced the antioxidant capacity measured by FRAP method. Organic farming and the location Chwałowice were characterized by higher values. Furthermore, anitioxidative capacity measured by FRAP method was correlated with chlorogenic acid content (r = 0.590**) and glutathione fractions, especially with the reduced form (GSH, r = 0.692**). Multidimensional comparative analysis (MCA) proved a better development of antioxidant properties of potato tubers in the organic cultivation system when compared with the integrated. Especially favorable were growing conditions at Boguchwała (organic) and worst at Młochów (integrated). From all investigated varieties, the best antioxidant properties were found in ‘Satina’ and ‘Jelly’. Clones TG-97-403 and 13-VIII-45 developed the weakest health promoting traits.

Impact of Conventional and Integrated Management Systems on the Water-Soluble Vitamin Content in Potatoes, Field Beans, and Cereals

The reduction of the environmental footprint of crop production without compromising crop yield and their nutritional value is a key goal for improving the sustainability of agriculture. In 2009, the Balruddery Farm Platform was established at The James Hutton Institute as a long-term experimental platform for cross-disciplinary research of crops using two agricultural ecosystems. Crops representative of UK agriculture were grown under conventional and integrated management systems and analyzed for their water-soluble vitamin content. Integrated management, when compared with the conventional system, had only minor effects on water-soluble vitamin content, where significantly higher differences were seen for the conventional management practice on the levels of thiamine in field beans (p < 0.01), Spring barley (p < 0.05), and Winter wheat (p < 0.05), and for nicotinic acid in Spring barley (p < 0.05). However, for all crops, variety and year differences were of greater importance. These results indicate that the integrated management system described in this study does not significantly affect the water-soluble vitamin content of the crops analyzed here.

Increasing ascorbate levels in crops to enhance human nutrition and plant abiotic stress tolerance

Ascorbate (or vitamin C) is an essential human micronutrient predominantly obtained from plants. In addition to preventing scurvy, it is now known to have broader roles in human health, for example as a cofactor for enzymes involved in epigenetic programming and as regulator of cellular iron uptake. Furthermore, ascorbate is the major antioxidant in plants and underpins many environmentally induced abiotic stress responses. Biotechnological approaches to enhance the ascorbate content of crops therefore have potential to improve both human health and abiotic stress tolerance of crops. Identifying the genetic basis of ascorbate variation between plant varieties and discovering how some 'super fruits' accumulate extremely high levels of ascorbate should reveal new ways to more effectively manipulate the production of ascorbate in crops.