Food scientists treat the cutting, slicing, and chopping of fresh vegetables as procedures that wound the cells of the plants and trigger injury-based responses by the plant cells. As a general rule, researchers treat vegetable chopping as a form of stress that is placed on the vegetables, similar to other forms of stress like extreme heat, extreme cold, dehydration, or other physical conditions.
While the idea of wounding and injury may sound entirely negative, it is important to remember that whenever we chew a vegetable, we are wounding and injuring the cells to an even greater extent, and it's the most natural first step for us in digesting our food and becoming optimally nourished. So the question isn't really about wounding or not wounding the vegetable cells; rather, what becomes important is when this process takes place and under what circumstances. After reviewing several dozen food science studies in this area, we have several practical recommendations about the cutting and chopping of fresh vegetables:
As a general rule, the more finely you shred or chop your fresh vegetables, the more quickly they should be eaten. For example, shredding lettuce within one hour of serving a salad may be able to increase your potential health benefits in comparison to shredding lettuce two to three hours before the salad is consumed.
The degree to which cutting impacts respiration rate in vegetables depends on the specific vegetable involved. Respiration (as measured by oxygen consumption) increases by 20% in uncut versus shredded endive; by 40% in uncut versus chopped broccoli; and by 100% in whole versus shredded lettuce. For shredded versus whole carrots, respiration can be increased by 300-700%. At the other end of the spectrum, respiration may only increase by 1-5% in the case of cut green beans or sliced zucchini. Because these differences aren't always logical, we recommend that you adopt the following general rule: to decrease the changes of spoilage, don't cut up fresh vegetables any further ahead of time than absolutely necessary.
Based on all of the research studies that we have reviewed, we are convinced that you can use some very common sense principles when you are making a decision about vegetable cutting. If you enjoy biting off a piece of fresh celery from the stalk, that approach makes very good sense to us as way to enjoy fresh celery. (Just make sure you do a good job chewing.) If you enjoy fresh chopped celery in a salad, that approach also makes sense. Just make sure to use a sharp knife in order to avoid unnecessary cell damage, and chop up the celery as close in time as possible to consumption of the fresh salad. Chopping size doesn't matter as much if you're immediately adding the vegetable to a soup, soaking it in a marinade, or fermenting it, as might be the case with shredded cabbage made into coleslaw or sauerkraut. If the chopping of a vegetable makes it easier for you to chew and digest the vegetable, then by all means do so. Fresh vegetables are meant to be enjoyed in a wide variety of ways!
Barry-Ryan C and O'Beirne D. (2000). Effects of peeling methods on the quality of ready-to-use carrot slices. International Journal of Food Science & Technology, 35 (2), 243—254.
Gleeson E and O'Beirne D. Effects of process severity on survival and growth of Escherichia coli and Listeria innocua on minimally processed vegetables. Food Control, Volume 16, Issue 8, October 2005, Pages 677-685.
Hodges DM and Toivonen PMA. Quality of fresh-cut fruits and vegetables as affected by exposure to abiotic stress. Postharvest Biology and Technology, Volume 48, Issue 2, May 2008, Pages 155-162.
Mandal SM, Chakraborty D, and Dey S. Phenolic acids acid as signaling molecules in plant-microbe symbioses. Plant Signaling and Behavior 5:4, 359-368; April 2010.
Murcia MA, Jimenez-Monreal AM, Garcia-Diz L, et al. Antioxidant activity of minimally processed (in modified atmospheres), dehydrated and ready-to-eat vegetables. Food and Chemical Toxicology, Volume 47, Issue 8, August 2009, Pages 2103-2110.
Song L and Thornalley PJ. Effect of storage, processing and cooking on glucosinolate content of Brassica vegetables. Food and Chemical Toxicology, Volume 45, Issue 2, February 2007, Pages 216-224.
Tiwari U and Cummins E. Factors influencing levels of phytochemicals in selected fruit and vegetables during pre- and post-harvest food processing operations. Food Research International, Volume 50, Issue 2, March 2013, Pages 497-506.
Vina SZ and Chaves AR. Respiratory activity and phenolic compounds in pre-cut celery. Food Chemistry, Volume 100, Issue 4, 2007, Pages 1654-1660.
Everything you want to know about healthy eating and cooking from our new book.
Order this Incredible 2nd Edition at the same low price of $39.95 and also get 2 FREE gifts valued at $51.95. Read more