The White Paper II
Have you read or heard about it? If not, continue reading, because the issues presented are hot topics among industry groups the past few months, including growers, wholesalers, bouquet makers and supermarkets. Dr. George Staby, founder of the Perishable Research Organization and the Chain of Life Network, and Dr. Michael Reid, Professor of Postharvest Horticulture and Postharvest Extension Specialist at the University of California, Davis presented their “White Paper II” in October 2005. It focuses on the relationship between temperature and vase life. Although the importance of temperature control on flower life is not exactly a new discovery, this paper delivers an industry-wide dope slap reminding us how crucial cold-chain management is in the general quality equation, starting at harvest and ending at purchase.
Staby and Reid not only define the problem and provide recommendations on how to overcome our pitfalls, they challenge industry groups, including the ASCFG, to encourage their representatives to discuss the subjects presented in the paper and, “…when feasible, take appropriate actions.”
Value Equals Longevity
The paper reminds us that flagging U.S. flower sales boil down to one thing: consumers feel flowers are not worth the money. How are they judging flower worth? Vase longevity in the home or workplace. Since temperature is critical to longevity, it makes sense to improve temperature management at every step on the front end to maximize vase life at the back end, i.e. the consumer’s home.
The authors point out the weaknesses and challenges that remind us how temperature influences flower and plant quality. A flower’s respiration rate (aging rate) increases as the temperature rises. When dry-packed flowers have a high respiration rate, the flowers deteriorate more quickly and the temperature inside the box rises. Of course, time plays a critical factor in temperature-related quality. The White Paper II provides data indicating that many flowers age three times faster at 50F than at 32F. At the same time, it takes about 20 minutes to get the field heat out of bunches once they are placed in a cooler, but when packed warm, it can take 2-4 days to cool a stack of warm flower boxes. The temperature parameters mentioned throughout the paper are slightly lower than the previous standard recommendations of 34-38F. Staby and Reid recommend wholesalers turn their coolers down to 33-34F, thereby decreasing shrink and increasing the revenue of each bunch by 2-5 cents. They recommend pre-cooling to 35F and rejecting boxes not cooled below 41F (32-35F preferred).
Another direct connection to temperature is ethylene damage. It has long been known that it takes more ethylene to cause damage at low temperatures. Keep in mind that ethylene-sensitive crops require a systemic postharvest treatment of STS or a gaseous exposure of 1-MCP, as well as temperature controls, to prevent the negative effects of ethylene exposure.
The White Paper continues with other effects of temperature, like stem bending in gerberas. Photos illustrate dramatic stem bending of gerberas within a narrow temperature window of 9 degrees (between 37F and 46F). Petal wilting in Asiatic lilies and floret drop in snaps within a certain temperature range are also (rather dramatically) shown through a series of photos within a temperature range.
It’s not just warm temperatures you want to avoid; fluctuating temperatures wreak havoc too because of the subsequent condensation development on the flowers or inside sleeves. Botrytis spores need at least four hours of continuous wetness to germinate, and condensation provides a perfect environment. Botrytis growth is maximum at 68F, but it can survive at temperatures as low as 30.5F. Micro-perforated sleeves help wick water off the flowers, but are not used extensively because many people (flower buyers) feel consumers are more likely to perceive freshness when flowers are in clear sleeves.
Maybe all this temperature information is giving you a headache because it’s not a big deal for your type of sales, but remember ethylene, botrytis, rapid aging, stem bending and floret drop all play a significant role in your immediate profitability, not to mention influencing consumer purchases, whether you sell at a farmers’ market or to a wholesaler.
If you sell to supermarkets, be aware that there is budding popularity among some of the companies most interested in your unique wares for offering consumers a guaranteed vase life. Temperature management is a critical specification in the guaranteed product handling protocols.
What tools can you use to improve your temperature management? The authors tested infrared, needle probe and computer-connected thermometer models and found the needle type attached to battery-operated digital readouts to be the best.
Once you have a temperature probe, calibrate it by stirring it in a cup of ice slurry for a minute to make sure it reads 32F. Calibrate once a month thereafter. If using a computer printout is more than you need to establish temperature management, digital probe types or a cooking thermometer also work.
The best way to read the temperature of your cooler is to measure several solutions in buckets placed at different levels and in different “corners”. If the flowers are packed in boxes and you want to make sure they are cold enough to load onto the truck, use a needle thermometer inserted through the pre-cooling hole into the head of the flower. If your probe is too large to stick into the flower without causing damage, poke it into the center of the box (through the cardboard).
The best location to test potted plants is in the soil. This paper reminds us that potted plants have the same postharvest requirements as cut flowers of the same species. Freesia was cited as an example: both the cuts and potted plant are ethylene and botrytis sensitive and require the same postharvest temperatures.
An obvious, but important, point mentioned in the paper was the comment that there’s no reason to measure temperatures if you don’t record it, share it with others and make appropriate changes as needed.
The paper provides several web sites as good sources of information on various temperature tools: www.chainoflifenetwork.org, http://.postharvest.ucdavis.edu, and http://www.ba.ars.usda.gove/hb66.
Please take the time to read the White Paper II in its entirety. The information is practical and can be accessed at the Chain of Life Network (site listed above)—a free information site that is user friendly and a good resource tool.