The only thing that matters is everything
Because we cannot take just one big step (kill step) to get us where we want to go, we must take many small steps all heading in the same direction to produce safe fresh fruit.
When I talk to folks about effective sanitation, lots of details come up: what kind of rag is best, what kind of cleaning methods should be avoided, the principle that you can’t sanitize a dirty surface, clean from top down, and many more.
Sometimes, I will get a little pushback like: “Seriously, does it really matter what kind of rag I use?” Probably not a lot, but why wouldn’t one at least consider using the best available option? There is some evidence that microfiber towels are superior to common terrycloth bar towels or cotton shop towels for both removing pathogens from surfaces and not transferring pathogens back to surfaces (1). The difference is not large, it’s not going to transform your sanitation program from average to excellent, but choosing the best tools for sanitation is not a trivial matter.
When it comes to tree fruit, a more significant detail to consider is washwater management. Contact time, sanitizer selection and concentration, and in the case of sodium hypochlorite, pH control are important variables that affect how well your fruit wash performs in reducing microbiological load. (I’ll leave out the effects of temperature, addition of soap, and mechanical scrubbing action for now.)
Most of us would agree that our wash systems would benefit from increased contact time, but doing much about that is usually a very expensive proposition and not something you are going to run out and change after reading this. What can we reasonably do right now? In the case of sodium hypochlorite, we can optimize concentration and pH. Research indicates that a total chlorine concentration of around 25 ppm at a “good” pH of 7.0 is not much better, if any better at all, than a freshwater rinse without sanitizer in reducing the microbial load on incoming fruit. Antimicrobial performance improves as concentration increases to 100 ppm (2, 3), and I think it is likely that dose response continues up to at least 150 ppm (personal communication, research in progress).
The reason I am given most often from those who favor low total chlorine concentration (<75 ppm) and the addition of little or no acidifying agent (pH >7.0) in stone fruit washwater is concern about fruit injury, usually staining. Staining is a type of skin discoloration that starts with abrasion injury. No abrasion injury, no staining. It has been reported that “pHs over 8.0‐8.5 induced dark staining (burning) in the different cultivars tested. Extremely darker skin staining was observed after the fruit was exposed to pH 9.0, 9.5 and 10.0 solutions in susceptible cultivars” (4). Add sodium hypochlorite, which increases pH, and don’t add acidifying agent to decrease pH, and what do you get? Increased staining potential and decreased antimicrobial activity.
In a nutshell, after 20+ years of following this issue, I have never seen stone fruit injury caused by properly-managed, single-pass wash systems using sodium hypochlorite at 100-120 ppm total chlorine at pH 6.8-7.0. Don’t miss the opportunity to reduce food safety risk by optimizing fruit wash parameters.
So, there’s two examples of details that matter. Obviously, one is more likely to have a significant effect than the other, but nevertheless, every detail, every step you take counts. Do what you can to take as many steps in the direction of reducing food safety risk as possible.