ARS | Publication request: Improving the Processing Quality of Existing Cultivars by Suppressing the Vacuolar Acid Invertase Gene

Submitted to: Proceedings Wisconsin Annual Potato Meetings
Publication Type: Proceedings
Publication Acceptance Date: January 21, 2011
Publication Date: February 1, 2011
Citation: Bethke, P.C., Bhaskar, P.B., Wu, L., Jiang, J. 2011. Improving the processing quality of existing cultivars by suppressing the vacuolar acid invertase gene. Proceedings Wisconsin Annual Potato Meetings. 24:27-28.

Technical Abstract: Storing potato tubers at low temperatures is highly advantageous in that it prevents sprouting, minimizes disease losses and increases the marketing window. Unfortunately, cold storage of existing cultivars causes an unacceptable accumulation of reducing sugars, a phenomenon referred to as cold-induced sweetening. Unappealing, dark-colored chips and fries are formed during frying when reducing sugars in cold-stored tubers react with amino acids in a non-enzymatic Maillard reaction. These fried products also contain acrylamide, and this has raised food safety concerns. Vacuolar acid invertase converts tuber sucrose into reducing sugars during cold storage. We hypothesized that by suppressing invertase gene expression we could address simultaneously the cold-induced sweetening and acrylamide problems. Potato clones derived from Katahdin, Snowden, Atlantic, MegaChip, and Dakota Pearl have been developed in which invertase gene expression is greatly reduced. Dramatically light-colored chips were produced from tubers of these clones directly from 39 °F storage for up to six months. Large reductions in tuber reducing sugar content and substantial improvement in chip color were observed in clones derived from all cultivars, and this suggests that the approach used is applicable generally. Potato chips from some clones had 15-20 fold less acrylamide than chips processed from control tubers after two weeks of cold storage. Plants with reduced vacuolar acid invertase gene expression grew as well as cultivar controls. In initial field trials, tuber specific gravities and yields from Katahdin-derived clones were comparable to Katahdin controls. These data point to vacuolar acid invertase as the key enzyme in cold-induced sweetening, and indicate a clear direction for maintaining fry color and reducing acrylamide in processed potato products.