Does processing vegetables & salad greens hold their nutrients and does processing of produce affect its nutrient content?
Farm to Fork?
After fruits and vegetables have been harvested, they continue to live, ‘breathe, and respire’ and have a limited shelf life.
This process consumes oxygen and produces carbon dioxide and water vapour.
The key to keeping products fresh for as long as possible is to reduce the respiration rate without harming the quality of the product – its taste, texture and appearance.
In general, the rate of respiration can be reduced by keeping the temperature low, having lower levels of oxygen in the packaging atmosphere and increased levels of carbon dioxide.
Nutrients in fruits and vegetables start to break down after harvest very rapidly. This loss of nutrients can be minimized by proper storage or processing. Fresh fruits and vegetables are picked, packed, and distributed to stores very quickly so that you get the freshest items available.
Storing fruits and vegetables in the refrigerator will prolong their shelf life and slow down the spoilage process, the tomato is my exception to maximize taste.
The three natural destroyers of vitamins in fruits and vegetables are heat, light, and oxygen. However, cooking and storing methods can help retain or destroy nutrients.
Here’s how:
Limit storage time. Fresh is always best when it comes to taste and nutrition.
Store fruits and vegetables in the refrigerator to slow spoilage. However, tomatoes are my exception. Their flavor is destroyed in the refrigerator. Hold them at room temperature. If you want to store produce items for a longer time, consider freezing them.
Raw is my first choice, cook minimally is an option like using steam to briefly cook vegetables until just crisp-tender. For example, asparagus and broccoli should retain their glorious bright green color when streamed.
Water-soluble nutrients are destroyed with prolonged cooking time. If you do cook vegetables in water, those nutrients will leach into the cooking liquid, so try to use the cooking liquids in soups.
Avoid slicing vegetables too far in advance. When we slice into a vegetable or fruit, we expose the cut surfaces to heat, light, and oxygen — they are nutrient destroyers. Better to wait to slice foods until we are ready to cook and eat them.
According to Mario G. Ferruzzi, a professor in the Department of Food, Bioprocessing and Nutrition Sciences at North Carolina State University, there are many variables including processing that will affect the nutrient content of food, but it may really depend on the nature of the product, the type and extent of processing and the actual nutrient we are talking about.
I am asked this question all the time, whats the difference between just picked farm fresh vegetables and bagged greens (pre-washed), frozen greens and canned vegetables?
First lets begin with the fact that Americans typically eat only one-third of the recommended daily intake (three servings instead of nine) of fruits and vegetables, and one of the root causes of chronic disease syndrome (lack of plant-based minerals) along with inactivity.
When looking at just farm fresh, bagged, frozen and canned vegetables, canned vegetables tend to lose a lot of nutrients during the preservation process (notable exceptions include tomatoes and pumpkin), frozen vegetables may be even more healthful than some of the fresh produce sold in supermarkets, says Gene Lester, Ph.D., a plant physiologist at the USDA Agricultural Research Center in Weslaco, Texas.
Why? Fruits and vegetables chosen for freezing tend to be processed at their peak ripeness, a time when—as a general rule—they are most nutrient-packed.
But what about bagged greens?
Washing and Chopping
Bagged greens are often pre-washed but washing intended to clean produce, can also damage plant tissues and expose them to oxygen dissolved in the washing water. This can cause a loss of vitamins that are water-soluble and sensitive to oxygen, such as vitamin C and the B vitamin folate.
All greens are washed to a certain extent, whether we’re talking about a fresh bunch of spinach right off the farm or the bagged version, but a triple-washed bagged spinach can create surface damage, provide opportunities for leeching or even facilitate oxidation reactions, all of which impact quality.
The first step of freezing vegetables is to blanch them in hot water or steam to kill bacteria and arrest the action of food-degrading enzymes—causes some water-soluble nutrients like vitamin C and the B vitamins to break down or leach out, the subsequent flash-freeze locks the vegetables in a relatively nutrient-rich state.
In general, minerals such as iron and calcium are largely stable in the plant. Losses may occur when heat is applied (as in the process of canning), but not as much through typical washing. Vitamins tend to be more sensitive to light, heat and oxygen. Beta-carotene, for example, is not very stable in the presence of oxygen or light,
On the other hand, fruits and vegetables destined to be shipped to the fresh-produce aisles around the country typically are picked before they are ripe, which gives them less time to develop a full spectrum of vitamins and minerals.
Outward signs of ripening may still occur, but these vegetables will never have the same nutritive value as if they had been allowed to fully ripen on the vine.
In addition, during the long haul from farm to fork, fresh fruits and vegetables are exposed to lots of heat and light, which degrade some nutrients, especially delicate vitamins like C and the B vitamin thiamin.
Bagging greens often involves a process known as modified atmosphere packaging. The amount of oxygen that typically exists in the atmosphere is reduced in the bag, replaced with an inert gas such as nitrogen.
In essence, less oxygen is available to react with nutrients which according to Professor Ferruzzi helps with the retention of color and the most oxidatively sensitive nutrients, like vitamin C, folate and beta carotene.
Bottom-line:
When vegetables are in-season, buy them fresh and ripe. “Off-season,” frozen vegetables will give you a high concentration of nutrients and are not as bad as people might say but today, you can get farm fresh vegetable delivered for every corner of the world.
If you think about it, for example, fresh lettuce or fresh spinach that’s picked and harvested … it might be washed and bundled … and it’s exposed to oxygen, light and moisture, and it’s getting sprayed with water to stay cold and fresh, and there’s significant nutrient loss occurring day by day.
With packaged greens, you may lose a little more up front during the initial processing, but depending on how they are packaged, you have the potential to control the rate of quality and nutritional declines when veggies are stored.
The same can be said for frozen veggies, which are initially blanched to inactivate enzymes that would otherwise break down nutrients and then frozen to stop bacterial spoilage, versus the natural degradation and rotting that occurs in fresh produce.
When you compare fresh string beans in a store vs. frozen, frozen will be almost always be higher in nutrient content, because they were picked and processed at the highest point of quality and then frozen to preserve them, according to Professor Ferruzzi. .
I recommend you choose farm fresh seasonal vegetables native to your state, county or country first, packages marked with a USDA “U.S. Fancy” shield, which designates produce of the best size, shape and color; vegetables of this standard also tend to be more nutrient-rich than the lower grades “U.S. No. 1” or “U.S. No. 2.”
Eat them soon after purchase when farm fresh: over many months, nutrients in frozen vegetables do inevitably degrade. Finally eat raw first, steam is a great option, not microwaved, rather than boil your produce to minimize the loss of water-soluble vitamins.
Canned vegetables are your last choice because the majority of canned vegetables tend to be higher in sodium since salt is often used as a preservative, but as I stated, Americans typically only eat only one-third of the recommended daily intake (three servings instead of nine) of fruits and vegetables so in the end, its about consuming more plant-based food especially for young children.
Finally, people tend to eat the same foods over and over again and purchase the same brands over and over again.
I recommend to rate the foods you eat, you have unlimited plat-based food to choose from, think about trying new fruits and vegetable that you have never eaten as they all have unique vitamin and mineral profiles that your body needs.
In the end, there is one final question to ask, are ‘organic’ vegetables better then non-organic vegetables? Stay tuned to my blogs and Ill answer that question .
One Day, One Meal, One Step At A Time!
LETS GO!
References
(1) Lisa Drayer, MA, RD, http://www.lisadrayer.com
(2) Dr. Mario Ferruzzi, ProfessorFood Science and NutritionDepartment of Food, Bioprocessing and Nutrition Science,
(3) Healthy Lifestyle Nutrition and Healthy Eating, Mayo Clinic, https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/organic-food/art-20043880
(4) Vitamin retention in eight fruits and vegetables: a comparison of refrigerated and frozen storage, Bouzari A1, Holstege D, Barrett DM, https://www.ncbi.nlm.nih.gov/pubmed/25526594