Which type of food has more nutritional value: Frozen or Fresh?
Since about the time I started to cook while living by myself for the last seven years, my grocery shopping visits have evolved from purely fresh based fruits and vegetables to frozen heavy carts. This evolution has brought me to stage where the freezer size in my refrigerator is a factor to be considered while hunting apartments.
The conversations with my peers and friends has always revolved around the fact that I might eating unhealthy food with lots of preservatives and almost most of them ended up in trying to convince me to move to fresh food. Given, my metabolism and workout routine during the pandemic, my energy levels and health seems to be unaffected if not better. The real world evidence contradicts what my friends were suggesting? Given the amount of repeated back and forths on multiple occasions, here’s my shot at trying to dig deeper.
Disclaimer: I have no background in nutritional science and this anaylsis is purely based on individual interest to optimize for time and nutrition.
Basics:
When we pick a produce, respiration aka oxidation occurs when the fruit or veggie begins to release heat and lose water impacting its nutritional quality. Fresh veggies produce enzymes, trypsin and chymotrypsin, that cause loss of color, flavor, and nutrients just after harvest. This enzymatic function can be halted by freezing. The process used to freeze is done by blanching — where produce is kept in boiling water for a short time and then put under iced water immediately after. This leads to preserving nutritional value. During this blanching process we might lose water soluble vitamins — B/C, although small amount. However, foods that are high in fat soluble vitamins like A/E and carotenoids are best kept frozen to preserve these nutrients as they are not water soluble and will retain it like carrot, broccoli, squash.
Comparison:
How fresh is the fresh produce?
The best discussion of the topic I found was from this paper from Harvard:
By the time fruits and vegetables reach your kitchen counter — whether from a stall at a local farmers market, or the supermarket produce department — several factors determine their nutritional quality: the specific variety chosen, the growing methods used, ripeness when harvested, post harvest handling, storage, extent and type of processing, and distance transported. The vitamin and mineral content of fruits and vegetables depends on decisions and practices all along the food system — from seed to table — whether or not that system is local or global.
The choice between frozen and fresh produce may seem difficult given how much nutrition misinformation there is circulating on social and traditional media. We are bombarded with advice to avoid frozen products at all costs, yet an examination of the available scientific research actually suggests the opposite. One study on vitamin retention in eight fruits and vegetables analyzed the ascorbic acid, riboflavin, a-tocopherol, and B-carotene content and found that the vitamin content of frozen foods was not only the same as their fresh counterparts, but even occasionally higher. This suggests that freezing produce is an effective method of preserving the vitamins and minerals in produce and, ultimately, providing you with optimal nutrients.
Manufacturers freeze vegetables at the peak of their freshness to preserve the nutritional value. Frozen produce is great to keep around in case you run low on fresh or if there are limited offerings at supermarket due to seasonality. They’re especially convenient when you don’t have time to clean and chop.
Berries that are grown with the intention of being frozen are exposed to a significantly lower amount of pesticides than their counterparts that are sent to the grocery store fresh. The reason for this is that fresh berries must maintain a good appearance for days, or even a week or more, as they are transported and then sold to consumers. This requires large amounts of pesticides and sprays to be administered before and after harvest. Thus, the berries that end up frozen have much lower levels of pesticide and crop spray exposure and residue. To display this dramatic difference between fresh and frozen we have taken data from the USDA pesticide testing program. The USDA data shows 52 different pesticide residues on a fresh blueberry vs. only 21 on a frozen blueberry.
One disadvantage of commercial food processing techniques is that they are poorly understood. Commercial food processing involves techniques that are difficult for the general public to grasp and that are out of their control, thus introducing a lack of transparency and generating suspicion and concerns about safety in some individuals.
Food safety
Another concern about food processing involves fears about food safety. In the 19th century, during the transition from farms and subsistence agriculture with home-processed food to urbanization and a commercially processed food supply that was ineffectively regulated, adulteration and other abuses in the manufacture of processed foods were common. Abuses led to a public outcry that drove the passage of the Pure Food and Drug Act of 1906 (37). Over the past century, food-borne illness crises have continued to erupt from time to time and their scope and distribution is often large because of today’s highly concentrated food processing and distribution system. Thus, a single source of contaminated eggs or beef can lead to food-borne illness in hundreds or thousands rather than tens of consumers. Such problems have led to concerns about the adequacy of hazard identification and risk reduction and have prompted calls for more rigorous regulation to avoid safety risks. It is a constant and dynamic challenge to keep pace with the changing food supply and to continue to maintain a safe food supply. Appropriate processing and preparation techniques for foods and a strong regulatory program are 2 essential means of safeguarding health in the face of these safety challenges.
Data Analysis:
Referencing both the papers listed below:
L-Ascorbic acid
Trans-β-carotene
Folate
Antioxidant activity:
Conclusion
Given the complexities of human body and the mechanism of nutrition absorption, the answer with respect to diet is always complicated. Some key takeaways
- Getting fresh farm veggies is always the ideal case i.e., the first step in the supply chain.
- “Freshness” in produce depends on transport and storage time.
- Depending on the time of year, grocery store, and your personal preference, it may actually save you time and money to choose some frozen foods over fresh.
- Overall, there is no systematic reduction in nutrient content as the result of processing of vegetables, and losses during prolonged storage of fresh produce can be severe.The loss of nutritional value must be weighed against other benefits such as convenience. Minimizing nutritional losses should be a goal of processing that is strived for whenever possible.
- In the cases of significant differences, frozen produce outperformed “fresh-stored” more frequently than “fresh-stored” outperformed frozen. When considering the refrigerated storage to which consumers may expose their fresh produce prior to consumption, the findings of this study do not support the common belief of consumers that fresh food has significantly greater nutritional value than its frozen counterpart.
- Choosing a mix of fresh and frozen can be a great way to maximize your vitamin and nutrient intake while stretching your dollar.
All That Matters Is if You Eat Them.
My freezer must haves:
- Berry mix/avocado chunks for smoothies
- Pomegranate and edamame seeds
- Chopped spinach/kale.
- Pre cut/peeled Okra, garlic and green chillies.
References:
Scientific References: https://onlinelibrary.wiley.com/doi/abs/10.1002/jsfa.2825
https://theness.com/neurologicablog/index.php/nutritional-content-of-produce/
