Background – Most if not all consumers are familiar with common household bleach containing sodium hypochlorite such as Clorox®. Another common but more stable form of bleach is called calcium hypochlorite, often referred to as swimming pool chlorine. A third but less familiar form of bleach is potassium hypochlorite. Nevertheless, the sodium, calcium, and potassium forms of bleach all have the same active ingredient, hypochlorous acid.
A potassium form of bleach called FloraFresh has been introduced to the floral industry. It is being sold to supermarkets for use in buckets and vases to hold, display, and sell cut flowers. The producer claims in part that it controls microbes, extends flower life, and eliminates bucket-scrubbing labor. The information presented here summarizes efforts to investigate some of these claims and other factors regarding this and other postharvest products under actual and simulated in-store supermarket conditions.
Chemistry – Mixing FloraFresh with deionized water at the recommended rate resulted in a 5.7 pH solution with 22 parts per million (ppm) free chlorine (the form of chlorine that kills bacteria best), 25 ppm total chlorine, and 86 ppm potassium. Compared to flower food and commercial holding products, FloraFresh contains no energy source (sugar) and is about 100 times less acidic.
Stability – When cut flowers were placed in freshly made FloraFresh solutions, free chlorine levels began to decrease (breakdown), which is normal, as it reacted with bacteria and organic matter such as stem tissue. These reactions continued for an average of 1.7 days under store display conditions at which time no free chlorine remained resulting in no further bacteria control. Factors that can affect the rate of FloraFresh breakdown include the number of flower stems placed in solution (more stems, faster breakdown) and flower species (stems with rough / hairy surfaces such as gerbera can result in faster chlorine breakdown compared to smooth stem species such as rose).
Microbes (introduction) – Bacteria associated with flower display or vase solutions can reduce flower life by physically blocking water uptake in stems and/or by producing damaging chemicals (including ethylene), even when stem blockage is not a problem. Measured in colony forming units (CFU), they represent the number of viable bacteria per milliliter (CFU/ml) in cut flower display and vase solutions or per gram stem weight inside flower stems (CFU/g). Regarding numbers of bacteria, levels as low as 10,000 to 1,000,000 CFU/ml can reduce flower life depending on flower species, bacteria type, and handling techniques, while levels over 10,000,000 CFU/ml can sometimes have no effect on flower life. In addition, vase solutions turning cloudy due to bacteria growth can lower consumer acceptance, even if flower longevity is not affected.
Microbes (results) – Of the 21 cut flower bucket display solutions tested from nine supermarket stores using FloraFresh, free chlorine was detected in four solutions, which also exhibited low bacteria levels averaging about 500 CFU/ml. The remaining 17 display solutions had no measurable free chlorine and contained an average bacteria level of 2,014,000 CFU/ml. Internal stem bacteria levels (bacteria that actually cause most stem blockage) from flowers in all 21 display solutions averaged 30,700,000 CFU/g. In addition, simulated in-store tests showed that FloraFresh display solutions exhibited an average bacteria level of 1,900,000 CFU/ml after three days at room temperature (to mimic in-store display), while internal stem bacteria levels from flowers held in these same solutions averaged about 4,000,000 CFU/g. Finally, the average of display solution and internal stem bacteria levels measured in all tests were about ten times higher under actual in-store conditions compared to simulated in-store tests.
Flower life – ‘Freedom’, ‘Katharina’, ‘Orchestra’, and/or ‘Vendela’ roses were purchased from six supermarket stores using FloraFresh, stems re-cut, and then placed in water, flower food, and/or FloraFresh solutions. Those placed in flower food solutions lasted 67% longer than those placed in water and 43% longer than those placed in freshly made FloraFresh solutions. In simulated in-store tests, ‘Rosita Vendela’ and ‘Gold Strike’ roses displayed in FloraFresh or commercial holding solutions for three days at room temperature (to mimic in-store display) before being removed (to mimic being sold), stems re-cut, and transferred to flower food solutions lasted 67% longer than roses displayed and sold in FloraFresh solutions.
Financial data – Information obtained from 14 supermarket companies having 10,315 stores in the US with combined sales of $271.1 billion in 2013 served as the foundation for the financial calculations used in this study. About 0.94% of store sales were estimated to be cut flowers, which translate to about $675 per day depending on company, store size, location, and the presence or absence of amenities such as pharmacies and gas stations. For such floral departments, the average costs per week for FloraFresh and commercial holding products were about $54 and $17, respectively. If as claimed by the manufacturer that bucket scrubbing labor can be eliminated when using FloraFresh, the labor cost savings were determined to be about $39 per week.
Summary – The key results obtained in this study can be summarized as follows.
- When FloraFresh was used under actual supermarket conditions, display solution bacteria were being controlled in only 19% of the solutions tested, while internal stem bacteria levels of flowers being held in these solutions were seemingly not being controlled and likely would rarely be controlled, the latter based on previously published research.
- The finding that solution and internal stem bacteria levels averaged about 10 times higher under actual (uncontrolled) verses simulated (controlled) store conditions suggests that using FloraFresh properly under actual store conditions requires better attention to label directions.
- Re-cutting stems and using flower foods at consumer level were always beneficial in extending flower life, regardless of previous FloraFresh or commercial holding solution treatments.
- When product and labor costs are considered, claimed labor cost savings at store level for not scrubbing buckets when using FloraFresh were essentially offset by increased FloraFresh costs when compared to commercial holding product costs.
Recommendations – The following recommendations are based on the results obtained in this study and information contained in 219 published research articles reviewed for this report.
- Make sure all stems are re-cut before putting flowers on display and that no leaves are in the solutions, both actions intended to reduce microbe loads and/or blockage.
- Regardless of display solution type, supermarkets should educate consumers on the importance of re-cutting stems and using flower foods for all flowers purchased except those sold in vases and arrangements.
- Flowers sold in vases and arrangements should already be in flower food solutions.
- Check for free (not total) chlorine in display bucket solutions daily when using any bleach formulation and change the solution when the test is negative (no measurable free chlorine).
- Wash all display buckets and vases between uses. In this regard, please consider the following two questions.
- Are you willing to drink out of glasses or cups that are never washed?
- If the answer is no, then why put flowers in unwashed containers?
In closing, the authors would like to acknowledge the input and/or products provided by various companies, organizations, and universities including Esprit Miami, Floralife, KJL Associates, FloraFresh, Penn State University, Prince & Prince, Produce Marketing Association, University of California, Davis, University of Perugia, Wageningen University, Chrysal Americas, and numerous supermarket companies. Please contact Dr. Staby (email@example.com) or Dr. Basel (firstname.lastname@example.org) with any comments and/or questions.
George L. Staby, Ph.D.
Perishables Research Organization
Florence, AZ and Elk Grove, CA
Richard M. Basel, Ph.D.
Food Safety Microbiologist
Efficacy of a Bleach-Based Product for Cut Flowers in Supermarkets