It’s good to be left in the dark (if you’re a potato)
As every potato expert knows, potatoes like darkness. Darkness slows greening, decreases potato weight loss, slows sprouting, and keeps tubers firm. Unfortunately, darkness does not align well with retail sales, since customers prefer bright lights and high-visibility packaging. Enter light-blocking film packaging: a lightweight, see-through packaging designed to showcase potatoes on the grocery store shelf and in consumers’ homes without tubers deteriorating due to bright light. Though light-blocking film packaging is now available from multiple manufacturers, no formal research has been done on how well it actually works… until recently.
Last year, Michigan State University’s School of Packaging, home of the nation’s best packaging research laboratory, conducted a shelf-life extension study on potatoes. The study’s goal was to scientifically determine the best packaging solution to prolong potato shelf life during retail storage.
The researchers analyzed physio-chemical changes in yellow, russet and red potatoes stored in various packaging types over four to six weeks at 22.5C, 40 per cent relative humidity, and 24 hour-per-day ultraviolet light.
The results were significant enough to impress even the packaging experts at MSU.
Potatoes lose weight when exposed to light because their temperature rises. The study showed that, in paper bags, this weight loss began virtually immediately. In conventional poly, potatoes began to lose weight between day three and eight. In light-blocker poly, potatoes held their original weight for over three weeks, only beginning to lose weight after three to four weeks (or more) of storage.
Potato greening, caused by tasteless and harmless chlorophyll formation, coincides with increasing levels of bitter tasting and, at high concentrations, unhealthy solanine (a glycoalkaloid). The USDA considers potatoes with more than five per cent green to be damaged and less than a US Grade #1.
The MSU study showed that greening occurred immediately in potatoes stored in conventional poly bags. In paper bags, yellow and russets potatoes greened after about three days; red potatoes greened beginning at about 20 days. In comparison, zero greening occurred throughout the entire storage period for potatoes stored in the light-blocker bags.
Taking all factors into consideration, the MSU study determined that light-blocker poly bags extended shelf life by between 12 and 18 days over traditional poly and paper bags.
To be honest, I wasn’t surprised by the results. The technology is an example of industry responding to an obvious need. It makes sense intuitively and it works in practice. What is more surprising, perhaps, is the slow uptake of light-blocking film in the market. Within the last 12 months or so we’ve seen industry starting to slowly gravitate towards this technology. I’d certainly expect significant uptake over the longer term given what a proven difference it makes to product longevity.