Fresh v.s. Frozen Foods: What you Should Buy to Preserve The Most Nutrients Possible in your Fruits and Vegetables: DEBUNKED
Nowadays, the word ‘FRESH’ seems to be one of the most popular and most marketed words in the food industry.
When processed foods experienced a manufacturing boost in the 1970s, research swiftly demonstrated to what extent these processed meats and ready-consumable dishes were unhealthy. Since then, people have begun to link processed foods with the label ‘unhealthy’, at the same time believing fresh foods are strictly the ‘healthy’ option. Nevertheless, the industry has since greatly developed in terms of food technology and many foods are now minimally and efficiently processed, such as frozen produce.
Recent research has demonstrated that the idea of ‘fresh is better than frozen‘ is no longer a universal truth, and might even be wrong in its entirety. This blog post will walk you through the difference in harvest, processing and transportation of fresh versus frozen fruits and vegetables, their difference in nutrient loss over time, which foods you should but frozen and which fresh, and how best to store these foods.
- Difference in Harvest, Processing, and Transportation of Fresh v.s. Frozen Fruits and Vegetables
- Fresh v.s. Frozen Nutrient Loss
- Which foods you should buy Frozen and Which you should buy Fresh
- How Best to Store Fresh & Frozen foods
- Conclusion
Difference in Harvest, Processing, and Transportation of Fresh v.s. Frozen Fruits and Vegetables
F for FRESH
Most fresh fruits and vegetables are picked before they are ripe, allowing them the time to further ripen during transportation. However, this also means they have less time to develop their full range of vitamins, minerals and antioxidants.
Fresh fruits and vegetables may spend anywhere between a few days up to 12 months in storage before reaching the supermarket, depending on the produce: while quickly-perishable foods like spinach will be shipped off quite quickly, foods like apples and potatoes can be stored for several months under controlled conditions while losing a minimal amount of nutrients (this is why supermarkets can offer apples all year round and their availability isn’t bound to a certain season).
During transportation, fresh produce is generally stored in a chilled, controlled atmosphere and treated with chemicals to prevent spoiling. Once they reach the supermarket, fruits and vegetables spend another 1-3 days on display after which they’re bought and stored in people’s homes for up to 7 days before being eaten. This means that there may be a period of 2 weeks (or much more in the case of apples or potatoes) between harvest and consumption, and ‘fresh fruit and veggies’ suddenly don’t sound so fresh anymore…
Thus, the greatest nutrient loss that fresh fruits and vegetables experience is during transport and storage. The more efficient and the shorter these steps are, the more the nutrients are protected.
F for FROZEN
Fruits and vegetables that will be frozen are usually picked at peak ripeness, which is when they are most nutritious. Once harvested, the vegetables are generally washed, blanched, cut, frozen and packaged, all within a few hours. Fruits are not blanched as this would destroy their texture. Instead, they are often treated with ascorbic acid (a form of vitamin C) and sometimes even sugar to prevent spoiling. Usually, no chemicals are added to the produce before freezing.
Freezing produce on a mass scale is a relatively new innovation for the food industry. When taking the example of the frozen pea, harvesting and transportation to a factory for washing, blanching and freezing takes just over 2 hours, while these same steps would have taken days to perform in the 1970s.
In comparison to fresh peas, the processing of frozen peas is much quicker, as speed is much more crucial when the produce is harvested at peak ripeness: as soon as the food is taken from the ground, it’s a nutritional race against time. Many vegetables including peas are nowadays individually quick-frozen: this is a super-cool kind of futuristic-sounding process in which high-speed fans blow cold air up towards the peas, making them fly about above the metal grate on which they were laid, until frozen. They’re then placed in cold storage until packaged.
While this fast-freezing process efficiently locks the vegetables in a relatively nutrient-rich state, the former step they go through – blanching – does cause a significant nutrient loss. Blanching consists of heating the produce in hot water or steam for a few minutes at high temperatures to kill bacteria and inactivate enzymes that degrade texture and color in the food during frozen storage.
This blanching causes some water-soluble nutrients like vitamins C and B to break down or leach out of the produce, while fat-soluble nutrients like vitamins A and E are often retained.
Thus, the greatest nutrient loss that frozen vegetables experience is during their pre-freezing blanching, while the nutrient loss thereafter is significantly reduced due to the frozen state of the produce.
Fresh v.s. Frozen Nutrient Loss in Fruits and Vegetables
Fresh fruits and vegetables produce enzymes called trypsin and chymotrypsin, that lead to loss of color, flavor, and nutrients following harvest. The nutrients are broken down because the fruit or vegetable actually wants to keep its own cells alive and therefore uses its own nutrients to achieve this. The fresh produce also undergoes an important process called respiration, which refers to the standard oxidation of fruits and vegetables. You can recognize respiration with the condensation you find on the inside of the plastic bag you put your veggies in: respiration is basically a loss of water, energy, and ultimately, nutrients. Even though fruits and vegetables are kept refrigerated while stored, they still lose a significant amount of nutrients over the total packaging-transport-storage time mainly through respiration.
When fruits and vegetables are frozen directly after harvest, they skip these nutrient-degrading processes. What they do go through though, is blanching, which causes a significant loss of nutrients all at once. Afterward, the nutrients are kept relatively intact since the nutrient-degrading process called respiration happens at a much, much slower rate when the produce is frozen.
Now this begs the question: What ultimately leads to more nutrient loss: Is either fresh or frozen produce more protective of the food’s nutrients?
A 2015 study compared the vitamin content in 8 different fresh and frozen fruits and vegetables – corn, carrots, broccoli, spinach, peas, green beans, strawberries, and blueberries. Overall, the vitamin content of the frozen commodities was comparable to and occasionally higher than that of their fresh counterparts. Beta-Carotene (a vitamin A precursor), however, was found to decrease drastically in some of the produce. The researchers also analyzed the amount of fiber, levels of phenolic compounds (good sources of antioxidants) and minerals like calcium, iron, zinc, and magnesium in the same 8 fruits and vegetables and found no significant differences between the fresh and frozen varieties.
In a 2017 study, researchers compared the nutritional value of fresh, frozen, and “fresh-stored” produce, meaning fruits and vegetables you tuck away in the fridge for five days (basically mimicking our typical storage patterns). The study included broccoli, cauliflower, corn, green beans, green peas, spinach, blueberries, and strawberries. Researchers evaluated vitamin C, beta-carotene, and folate (vitamin B9). Overall, there was usually no significant difference in vitamin content between fresh, frozen, or fresh-stored food. When there was a significant difference though, frozen produce outperformed “fresh-stored” more frequently than “fresh-stored” outperformed frozen.
Overall, these findings point to frozen fruits and vegetables possibly being slightly superior to fresh ones. The reason that some foods show no difference in nutritional value between being frozen or fresh while others show either a fresh or frozen superiority, is because different nutrients in different kinds of produce degrade at different rates.
Which foods you should buy Frozen and Which you should buy Fresh
Water-Soluble v.s. Fat-Soluble Vitamins
While it would be best to look at the nutrient profile of each individual fruit and vegetable type to know whether frozen or fresh is better, fruits and vegetables can grossly be divided in two dinstinct groups which provide an indication of whether the food will retain most nutrients in a fresh or a frozen environment. One research found that foods with primarily water-soluble nutrients, including vitamins C and B, retained nutrients differently than those with mainly fat-soluble nutrients, including vitamins A and E.
The researchers concluded that fresh produce is often best for vitamin C content, as this vitamin is highly sensitive to heat – which is an issue in the face of blanching – as long as it undergoes minimal storage. The problem with this research, however, is that they looked only at ‘fresh’ produce and not at ‘fresh-stored’ produce, which is a lot more relevant since individual storage in the fridge is most likely to happen before consumption.
According to the study, foods with more vitamin E and A, which are found in high amounts in carrots and tomatoes for instance, fared much better during heat treatment (especially in the case of canned foods, as canning requires high-heat treatment), and would thus be better to buy either frozen or canned.
It thus seems that fruits and vegetables rich in water-soluble vitamins may be better to buy fresh if consumed rapidly, while produce high in fat-soluble vitamins is better when bought frozen.
Seasonal v.s. Out-Of-Season
Furthermore, it may be better to buy out-of-season fruits and vegetables frozen rather than fresh. The reason for this is that when a food is out of season, it is often imported from a faraway country, meaning the transportation and storage times are longer which can lead to additional nutrient losses (the extended transportation also accounts for extra pollution). Freezing skips this issue as the produce may be locally harvested and then frozen in order to be sold when it is ‘out-of-season’. In reverse, local in-season foods may be better when bought fresh and rapidly consumed.
What about Meat and Fish?
Up to now, we’ve only discussed fruits and vegetables. There is, however, something interesting to say when it comes to other types of food such as meat and fish. Following the same logic as explained above, meat and fish (especially red meat and fatty fish) being foods high in fat-soluble nutrients, are probably better when bought frozen than fresh. Freezing meat and fish also preserves the omega-3 fatty acids better, which are anti-inflammatory healthful fats that help in cell membrane, brain and hormone function.
In addition, there is a crucial difference between fruits/vegetables and meat/fish which makes buying frozen meat and fish all the more logical. In fruits and vegetables, cells remain alive after harvest, and thus cell viability of frozen-thawed tissues is a key factor that needs to be considered during freezing, while muscle cells in meat and fish lose their viability after slaughter/catch, and therefore there is no need to consider their cell viability. The effect of freezing and subsequent thawing of fruits and vegetables is the topic of ongoing research, something which is (luckily) not a matter of concern in the case of meat and fish.
How Best to Store Fresh & Frozen foods
The three factors that lead to nutrient loss are heat, oxygen, and light. This means that food is best kept in a cool, dark and closed environment.
The Dangers of Cutting
The interior of uncut produce is protected from oxygen and light, but becomes exposed when cut. The nutrient that suffers the most in cut fruits and vegetables is vitamin C, although some vitamin A and E is lost as well. These vitamins are antioxidants, which are normally naturally protected by the peels and coverings. Once you break through the protective coverings, the flesh inside is exposed to air and the oxygen reduces the antioxidant vitamins.
Vitamin C is carried by water, which is why it is easier for it to leak out in the fluids released after cutting, or in the water you use to either rinse or cook the produce. Vitamins that are carried in fat, such as vitamin D, does not leach out as easily. Fat-soluble vitamins in general are more stable in food than water-soluble vitamins.
Large chunks and Sharp knives
The best way to store fruits and vegetables is to leave them unwashed with the skin or rinds intact until you plan to eat them. When you cut them, cut them in large chunks, as less surface area means less oxygen exposure and more vitamin retention. This accounts both for storage (in an air-tight container in the fridge or freezer, preferably dark) and for cooking (whether steaming, boiling or pan-frying). When cutting, use a sharp knife, as this doesn’t bruise the produce as much as a dull blade.
Air-tight containers are Key
When storing frozen food, make sure to also use air-tight containers: while the respiration process of fruits and vegetables occurs at a much lower rate at freezing temperatures, it still occurs since the produce is exposed to oxygen, especially when the freezer is opened often. Considering frozen produce is kept for a much longer time in the freezer (several months), the aggregated oxygenation may be worrisome if the produce is not stored in an air-tight container. The best jars to store any fresh or frozen produce are containers called ‘Miron Violetglass’ jars, which seemingly have been around since the time of the Ancient Egyptians and protect as well as preserve foods like nothing ever seen before.
Conclusion
The question of whether you should buy your fruits and vegetables either fresh or frozen is a hard one, as there is no one-rule-fits-all answer to this and research remains relatively inconclusive.
Overall, frozen foods seem to do slightly better than fresh foods in terms of nutrient preservation. Recent research suggests that produce high in water-soluble nutrients (vitamins C and B, like spinach and citrus fruits) is better to buy fresh if consumed rapidly, while produce rich in fat-soluble nutrients (vitamins A, D, E and K, like carrots and avocados) is better to buy frozen. Also, buying meat and fish frozen may be better, and buying out-of-season produce frozen while buying local, in-season produce fresh is better.
The distinction depends on many factors: how the produce was harvested (the quality of the soil, geographic and climate conditions), the time and conditions in which it was transported and stored (temperature, oxygen level, etc.). To make it simple, buying fresh foods is a good idea only when they are stored properly in the fridge eaten relatively quickly, and buying frozen foods is a good idea only if they are well-stored in air-tight containers in the freezer, no longer than the expiration date.
Cutting your food into larger chunks, using a sharper knife, storing in dark air-tight containers, and using less water to boil or steam the produce (and even re-using this nutrient-rich water) are methods to prevent nutrient loss and thereby improve the quality of your fruits and vegetables.
