Glycoalkaloid Development during Greening of Fresh Market Potatoes (Solanum tuberosum L.)

Abstract

Chlorophyll and glycoalkaloid synthesis in potato (Solanum tuberosum L.) tubers occur in direct response to light. The two processes are concurrent, but independent. Color photographic indices to subjectively grade fresh market potatoes for the extent of greening were developed under lighting conditions consistent with those of retail markets. Total glycoalkaloid (TGA) and chlorophyll accumulation for four cultivars were determined over the respective greening scales, thus calibrating the scales for TGA content. On average, TGA concentrations in complete longitudinal sections of tubers (flesh samples) were highest in Dark Red Norland followed by Russet Norkotah, Yukon Gold, and White Rose. TGA concentrations of flesh samples of White Rose and Yukon Gold tubers were somewhat variable and did not increase in direct proportion to greening level and chlorophyll content, particularly at higher levels of greening. TGA concentrations in Dark Red Norland and Russet Norkotah tubers were highly correlated (P < or = 0.001) with greening level and chlorophyll concentrations. When averaged over greening levels, skin samples contained 3.4- to 6.8-fold higher concentrations of TGAs than flesh samples, depending on the cultivar. The TGA concentration in periderm samples ranged from 37 to 160 mg/100 g of dry wt. Regardless of greening level, concentrations of TGAs in the flesh samples (including attached periderm) remained within limits presumed safe for human consumption. Discrimination of greened tubers on the basis of perceived glycoalkaloid toxicity is likely unfounded for the cultivars and greening levels studied.

Variation for Tuber Greening in the Diploid Wild Potato Solanum Microdontum

“…Grunenfelder et al (2006a) illuminated at 50 ft candles to match the retail environment, but noted that "lighted displays" in grocery stores were often closer to 200 ft candles. Other research on greening and glycoalkaloids has commonly been based on much brighter and longer illumination.…”

“…Grocery Store Practices and Losses Grunenfelder et al (2006a) report that produce departments of grocery stores routinely discard greened potatoes. In lieu of more detailed published reports of culling and associated losses, we conducted our own informal (unpublished) telephone survey of six produce managers at major chain groceries in Wisconsin.…”

Potato glycoalkaloids: formation and strategies for mitigation

“…GAs affect the nervous system by interfering with the body's ability to regulate acetylcholine, a chemical responsible for conducting nerve impulses. The mechanism of toxicity described in the literature42 consists of two processes: disruption of the phospholipids in membranes43 and inhibition of acetylecholinesterase,44 the latter resulting in depression of the central nervous system and the neurological effects observed during poisoning (hallucinations, convulsions, depression etc. ).…”

Potato Steroidal Glycoalkaloids: Biosynthesis and Genetic Manipulation

“…As SGAs are not destroyed during cooking (Maga 1994;Smith et al 1996), an upper limit of 20 mg per 100 g fresh weight in potato tubers has been established for the release of commercial cultivars . However, factors associated with growth, harvest and postharvest treatments, such as drought (Bejarano et al 2000), high temperature (Morris and Petermann 1985;Lafta and Lorenzen 2000), light exposure of tubers (Dale et al 1993;Percival et al 1994;Grunenfelder et al 2006) and wounding (Bergenstråhle et al 1992;Choi et al 1994), may elevate tuber SGA content. Moreover, organically grown potatoes have been reported to contain elevated levels of glycoalkaloids (Hajslova et al 2005;Wszelaki et al 2005;Abreu et al 2007).…”