The findings, published in PLoS One, come from research investigating new methods to increase levels of broccoli's much mooted anti-cancer compounds glucosinolate (GS) and quinone reductase (QR - an in vitro anti-cancer biomarker) through the use of natural plant based compounds.
However, while researching methods to increase these suggested beneficial compounds, the US-based team also found a way to prolong the vegetable’s shelf life - offering up a natural and inexpensive method to produce broccoli that has even more potential health benefits and won’t spoil so quickly in storage.
“We had figured out ways to increase the anti-cancer activity in broccoli, but the way we figured it out created a situation that would cause the product to deteriorate more rapidly after application,” explained Jack Juvik from the University of Illinois - who led the research. “For fresh-market broccoli that you harvest, it’s not too big a deal, but many of these products have to be shipped, frozen, cut up, and put into other products."
“If we could figure out a way to prolong the appearance, taste, and flavour long after harvest and maintain the improved health-promoting properties, that’s always of great interest to growers,” he added.
Juvik and his team first used methyl jasmonate (MeJA), a non-toxic plant-signal compound that is produced naturally in plants to increase the broccoli’s anti-cancer potential, which they sprayed on the broccoli about four days before harvest.
When applied, MeJA initiates a process of gene activity affiliated with the biosynthesis of glucosinolates (GS), which have been identified as potent cancer-preventative agents because of their ability to produce enzymes, such as quinone reductase (QR), that detoxify and eliminate carcinogens from the human body, explained the researchers.
However, during this process, MeJA the team found that also signals a network of genes that lead to plant decay, by inducing the release of ethylene, explained Juvik.
“While we can use MeJA to turn on phytochemicals like the glucosinolates and dramatically increase the abundance of those helpful anti-cancer compounds, MeJA also reduces the shelf life after harvest,” he said.
Therefore the researchers tried using a recently developed compound known as 1-methylcyclopropene (1-MCP), which has been shown to interfere with receptor proteins in the plant that are receptor-sensitive to ethylene.
By applying the compound after harvesting to the same broccoli that had already been treated with MeJA before harvest, the team hoped to procude broccoli with increased levels of GS without the issues relating to shelf life.
Like MeJA, 1-MCP is also a non-toxic compound naturally produced in plants, although Juvik noted that synthetic forms can also be produced.
“It’s very cheap, and it’s about as toxic as salt. It takes very little to elevate all the desirable aspects. It’s volatile and disappears from the product after about 10 hours,” he said - stressing that both the MeJA and 1-MCP sprays required very small amounts of the compounds.
Food security and battling malnutrition
Juvik suggested that use of the new method could make a great impact on important global dilemmas such as food security issues and health-care costs.
“It’s a fairly cheap way to maintain quality, but it provides a preventative approach to all the medical costs associated with degenerative diseases," he said.
"It’s a way to protect people by reducing the risk they currently have to different diseases. It won’t take it away, but it could prevent further damage,” he said.
As for its impact on impending global food security concerns, Juvik commented that any mechanism which improves people’s health, especially later in life, will benefit food security.
“We need to look at what mechanisms we can use to improve not only food security but the functioning of people later in their life spans," he said.
"When you look at how much the United States spends on medical costs associated with these diseases, you see it’s a huge burden on the economy, which is the same in all countries. It basically takes away resources that could be used to improve food security,” Juvik opined. “Also, promoting and prolonging food stability with quality after harvest means less waste, which is a big issue in terms of food security.”
Source: PLoS One
Published online ahead of print, doi: 10.1371/journal.pone.0077127
“Methyl jasmonate and 1-Methylcyclopropene treatment effects on quinone reductase inducing activity and post-harvest quality of broccoli”
Authors: Kang Mo Ku, Jeong Hee Choi, Hyoung Seok Kim, Mosbah M. Kushad, Elizabeth H. Jeffery, John A. Juvik