Submitted to: Journal of Agriculture and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 23, 2009
Publication Date: January 25, 2010
Citation: Mccann, L.C., Bethke, P.C., Simon, P.W. 2010. Extensive Variation in Fried Chip Color and Tuber Composition in Cold-Stored Tubers of Wild Potato (Solanum) Germplasm. Journal of Agriculture and Food Chemistry. 58(4):2368-2376. Interpretive Summary: Approximately half of the annual U.S. potato crop is used for the production of potato chips and French fries. Quality standards established by industry dictate that these fried potato products must be light colored to appeal to consumers and avoid unpleasant flavors. Potatoes are stored for up to 10 months, and low temperature storage minimizes weight loss, rot and undesirable tuber sprouting. Storing potatoes at low temperatures, however, results in an accumulation of sugars that produce dark colored, bitter tasting products during frying. In this research, wild relatives of cultivated potato were grown in two locations for several years. Harvested tubers were evaluated for their ability to maintain low sugar contents during low-temperature storage and to produce light colored chips after frying. Large variation in these parameters was found within these wild potato relatives, with several having better low-temperature storage capabilities than current varieties of potato. These “cold chipping” species are attractive candidates for breeding efforts focused on developing improved potato varieties that can be stored at low temperatures. Such varieties would decrease product losses in storage, and eliminate or reduce the use of chemicals to prevent sprouting in storage. This would benefit growers and consumers by minimizing waste resulting from rot, keeping the quality of processed potato products high throughout the year, and providing a more consistent supply of tubers late in the storage season.
Technical Abstract: Cold-induced sweetening and browning in the Maillard reaction have driven extensive research in the areas of plant physiology, biochemistry, and food science in Solanum tuberosum. To date, research in these areas excluded wild relatives of potato. This is the first assessment of cold-stored tuber composition in diverse wild Solanum. Thirty-six plant introductions (PIs) encompassing 19 species that chipped light and dark after 3-4 months storage at 1-2'C were selected from an extensive evaluation conducted previously by others. S. berthaultii, S. chacoense, S. medians, S. multiinterruptum, S. phureja, S. pinnatisectum, S. raphanifolium, S. sparsipilum, S. stoloniferum, and S. tuberosum subsp. andigenum were represented by multiple PIs to evaluate intra-specific variation. Additional plant introductions of S. chacoense, and S. pinnatisectum were added in later years based on preliminary light chip color data for these species. S. tuberosum cv. Snowden and four S. tuberosum haploid x species hybrid clones from the USDA Potato Enhancement Laboratory were clonally propagated and used as controls. Plants were grown in Madison and Rhinelander, WI, over four years and harvested tubers were stored at 2°C for 2-3 months prior to evaluating them for fried chip color, and content of sucrose, glucose, fructose, asparagine and dry matter. Extensive inter- and intra-specific variation for chip color and tuber composition was found. Tuber sugar profiles indicated that invertase activity at low temperatures differed between and within species. Tuber fructose, glucose, and sucrose concentrations partially explained chip color variation in most accessions, but asparagine concentration and percent dry matter did not. Cold-induced sweetening and the Maillard reaction occurred in most wild species similar to that in S. tuberosum, but S. pinnatisectum was unique.