Refrigerated vs Freeze Drying vs Dehydrating: What Happens to the Nutrients in Your Microgreens?
The Decline of Nutrients in Modern Food: What Happened?
If you’ve ever wondered why fruits and vegetables don’t seem to pack the same nutritional punch they once did — you’re not imagining it. Research over the past 50 years has documented a significant decline in the nutrient content of fresh produce, driven by changes in farming practices, soil depletion, crop breeding, and global supply chains.
You may be familiar with the phrase “fresh is best”, and it would be great if that's all we had to consider today when thinking about food - but unfortunately that's not the case. Freshness isn’t the whole equation. Today, “freshness”, even freshly harvested, does not mean the product is nutritionally dense.
At Natural Yield we encourage people to grow nutrient dense food at home or as close to home as you can (e.g. community gardens). Microgreens have more nutrient density than their adult counterparts, which is why we particularly encourage growing microgreens.
As a general statement it's fair to say that as soon as something is harvested it begins to lose its freshness. This article explores some data around refrigeration, dehydration and freeze drying as methods of keeping product fresh and preserving nutrients.
What the Data Says
A comprehensive study published in the journal Horticultural Science (Davis et al., 2004) compared USDA nutrient data from 1950 to 1999 across 43 garden crops:
- Calcium, iron, and phosphorus declined by as much as 30%
- Vitamin C and riboflavin also showed significant reductions
- Protein levels in some vegetables fell by 6–38%
Similar trends have been confirmed in studies from the UK, Canada, and Australia.
What’s Causing Nutrient Decline?
| Cause | Effect on Nutrition |
| Soil degradation | Overfarming depletes organic matter and microbial life |
| Synthetic fertilisers | Prioritise rapid growth over mineral complexity |
| Crop breeding for yield | Focus on size and appearance, not nutrition |
| Long-distance transport | Early harvesting reduces nutrient maturity |
| Storage and handling | Cold storage and light exposure degrade nutrients further |
The faster and bigger we grow food, the more we dilute its nutrient density.
What Can Be Done?
- Regenerate soils with compost, cover cropping, and microbes
- Choose local, seasonal produce grown in mineral-rich soil
- Grow food at home, especially microgreens and sprouts
- Use freeze drying to preserve nutrients post-harvest
- Eat as close to harvest as possible - growing your own makes this easy!
Definitions
What is Freeze Drying?
Freeze drying (lyophilisation) removes water from produce by freezing it and then using vacuum pressure to convert ice directly into vapour. This protects heat-sensitive nutrients like vitamin C, B-complex vitamins, chlorophyll, and antioxidants.
What is Dehydrating?
Dehydration removes moisture by applying heat and airflow, typically at 50–70°C. It’s economical, but can degrade nutrients and change texture, colour, and flavour. Dehydration also leaves more residual moisture, shortening shelf life and reducing potency per gram.
What is Refrigeration?
Refrigeration slows down the natural spoilage of fresh produce by lowering the temperature, typically to around 4°C. This reduces enzymatic activity and microbial growth, extending the shelf life of fresh microgreens to around 7–10 days.
However, refrigeration does not stop nutrient loss — particularly for water-soluble vitamins like vitamin C and B-complex, which begin to degrade within days, even under optimal cold storage conditions.
Refrigeration is ideal for short-term freshness, but not for long-term nutrient preservation.
Nutrient Loss in Fresh Microgreens Over Time
While fresh microgreens are vibrant and nutrient-dense straight after harvest, they’re also incredibly perishable. Even when stored in the fridge, nutrient levels begin to decline within days — particularly for water-soluble vitamins like vitamin C and B-complex.
What the Research Shows
Studies on post-harvest storage of leafy greens and sprouts (including broccoli, radish, and kale microgreens) have shown:
What Causes Nutrient Loss in Fresh Storage?
❗ Up to 50% of vitamin C can be lost within 7 days, even under ideal refrigerated conditions. |
Why This Matters
For consumers trying to eat more microgreens for their nutritional benefit, the time between harvest and consumption matters a lot. If you’re not eating microgreens within 3–5 days, you may be missing out on much of their health potential.
Freeze Drying Locks It In
At Natural Yield, for our Potent Powder range, we harvest and freeze dry our microgreens immediately to lock in peak nutrition. This ensures you're getting the full spectrum of vitamins, minerals, and antioxidants — even months later — without worrying about nutrient loss in the fridge.
Nutrient Retention: Freeze Drying vs Dehydrating
- Freeze drying retains 85–95% of vitamins and antioxidants
- Dehydration retains 40–60%, sometimes lower for vitamin C
- Freeze drying preserves texture and colour better
There’s a good amount of data on nutrient retention in freeze-dried vs dehydrated fruits and vegetables — and the differences are significant depending on the nutrient, the food type, and the method used.
Here’s a breakdown of key findings from scientific literature and food science resources:
Nutrient Retention: Freeze Drying vs Dehydration
| Nutrient Category | Freeze Drying | Dehydration (Hot Air Drying) |
| Vitamins (esp. C & B-complex) | High retention (up to 90–95%) | Poor retention (40–60% typical, vitamin C especially fragile) |
| Minerals (Ca, Fe, Mg, Zn) | Excellent retention (minimal losses) | Good retention (slightly more loss than freeze drying) |
| Proteins | Largely unaffected | Minor degradation possible at high temps |
| Fats | Stable, but prone to oxidation if exposed to air | More prone to degradation due to heat & air exposure |
| Antioxidants | High retention, especially in berries & leafy veg | Moderate to poor retention depending on drying temp |
| Enzymes | Mostly inactivated (good for shelf life) | Denatured by heat (inactivates nutritional enzymes) |
| Taste/Colour/Texture | Closely resembles fresh | Often darker, leathery, and with stronger “cooked” taste |
Example Comparisons
| Food Item | Vitamin C Retention (Freeze Dried) | Vitamin C Retention (Dehydrated) |
| Strawberries | ~92% | ~50% |
| Spinach | ~85% | ~35–45% |
| Broccoli | ~90% | ~40–50% |
| Apples | ~88% | ~55% |
(Sources: USDA studies, Journal of Food Composition and Analysis, Food Chemistry, Comprehensive Reviews in Food Science and Food Safety)
Summary Table: Nutrient Retention in Microgreens by Drying Method
| Nutrient Type | Freeze Dried (Est.) | Dehydrated (Hot Air, Est.) |
| Vitamin C | 85–95% | 30–60% |
| Total Phenolics | 90–95% | 50–70% |
| Chlorophyll | 90%+ | 40–60% |
| Enzymes | Inactive but preserved | Inactivated and degraded |
| Sulforaphane | 80–95% | 30–50% |
| Flavonoids / Antioxidants | 90–95% | 50–70% |
(Estimates based on leafy green and brassica research — specific data on microgreens is emerging but consistent with this trend)
Why Freeze Drying Is Better for Nutrients
- Low-Temperature Process: Freeze drying happens under vacuum at temperatures below freezing, avoiding heat-sensitive nutrient loss.
- No Cooking: Unlike dehydrating, freeze drying doesn’t "cook" the food, preserving volatile vitamins (like vitamin C, thiamine, and folate).
- Minimal Oxidation: Vacuum environment reduces exposure to oxygen, which protects antioxidants and fats.
Practical Considerations
| Factor | Freeze Drying | Dehydrating |
| Shelf Life | 15–25 years (when sealed) | 1–5 years (depends on storage) |
| Rehydration | Rapid, retains texture & flavour | Slower, texture often leathery |
| Equipment Cost | High (freeze dryers are expensive) | Low (dehydrators are affordable) |
| Storage Space | Light and compact (very little water) | Also compact, but may weigh more |
Nutrient Retention in Microgreens During Drying
There’s limited direct research on freeze-dried vs dehydrated microgreens, but the data we do have (and can infer from broader leafy green studies) strongly supports the idea that:
Freeze drying is far superior for preserving microgreen nutrients.
This is especially true for:
- Vitamin C
- Chlorophyll
- Enzymes
- Polyphenols and flavonoids
- Sulforaphane (in brassicas like broccoli microgreens)
What the Research Tells Us
- USDA Study on Broccoli Microgreens (2012)
Found that broccoli microgreens had 4–40x more nutrients than mature broccoli. These nutrients include vitamin C, E, K, lutein, and beta-carotene — all highly sensitive to heat and oxidation. The implication: any drying process must protect these volatile nutrients. - Study: Effects of Drying Methods on Kale Leaves (proxy for microgreens)
Freeze drying preserved 95%+ of vitamin C, total phenolics, and antioxidants. Hot air drying retained only 30–60% depending on the temp used (often 50–70°C). - University of Maryland / FDA Collaborative Work
Suggests that freeze-dried microgreens maintain much of their bioactive profile, especially in the brassicaceae family (e.g. mustard, broccoli, radish). - Chlorophyll and Sulforaphane Stability
These sensitive compounds degrade rapidly with heat. Freeze drying preserves them almost fully, whereas dehydration can degrade 40–70%.
Why Dehydration Has More Nutrient Loss
Heat Exposure: Dehydration (typically at 50–70°C) damages vitamin C, B1 (thiamine), B2 (riboflavin), and folate.
Oxygen & Light: Extended drying time under ambient air and light can oxidise nutrients.
Water Activity Reduction: Dehydration doesn’t reduce water activity as much as freeze drying, potentially shortening shelf life or promoting minor microbial activity over time.
Water Loss and Why It Matters for Potency
| Method | Avg. Water Loss | Dry Matter | Potency Factor (vs Fresh) |
| Freeze Drying | ~95% | ~5% | ~20x |
| Dehydrating | ~85–90% | ~10–15% | ~7x to 10x |
A single gram of freeze-dried microgreens delivers the nutrients of ~20g fresh.
Adjusted Nutritional Value per Gram (Factoring Potency & Loss)
| Nutrient | Freeze Dried (Potency × Retention) | Dehydrated (Potency × Retention) |
| Vitamin C | 20 × 0.85 = 17x fresh | 7 × 0.50 = 3.5x fresh |
| B Vitamins | 20 × 0.85 = 17x fresh | 7 × 0.60 = 4.2x fresh |
| Minerals | 20 × 0.95 = 19x fresh | 7 × 0.85 = 6x fresh |
| Proteins | 20 × 1.00 = 20x fresh | 7 × 0.95 = 6.65x fresh |
| Antioxidants | 20 × 0.90 = 18x fresh | 7 × 0.60 = 4.2x fresh |
| Sulforaphane | 20 × 0.85 = 17x fresh | 7 × 0.40 = 2.8x fresh |
Nutrient Retention and Potency Comparison
| Nutrient | Fresh Microgreens | Freeze-Dried Microgreens | Dehydrated Microgreens |
| Water Content (%) | ~90–95% | ~5% | ~10–15% |
| Dry Matter (%) | ~5–10% | ~95% | ~85–90% |
| Potency Factor | 1x | ~20x | ~7–10x |
| Vitamin C Retention (%) | 100% | 85–95% | 40–60% |
| B-Complex Vitamins Retention (%) | 100% | 85–95% | 50–70% |
| Minerals Retention (%) | 100% | 90–95% | 80–90% |
| Proteins Retention (%) | 100% | ~100% | ~95% |
| Antioxidants Retention (%) | 100% | 90–95% | 50–70% |
| Enzymes Retention (%) | 100% | Inactivated but retained | Denatured |
| Chlorophyll Retention (%) | 100% | 90–95% | 40–70% |
| Sulforaphane Retention (%) | 100% | 80–95% | 30–50% |
| Flavor & Color | Fresh | Fresh-like | Altered |
| Rehydration Speed | N/A | Fast | Slower |
| Shelf Life | 5–10 days | 10–25 years (sealed) | 1–3 years (sealed) |
Final Thoughts
Think about how you get the best of both worlds of nutrient dense freshness and preserved nutrients. Not everyone can buy a freeze dryer! They are expensive. But just about everyone can grow their own microgreens, which is a great start!
Freeze drying is not just about shelf life — it’s about locking in nutrients at their peak. Compared to dehydration or aging in the fridge, freeze-dried microgreens deliver unmatched potency, stability, and versatility.
At Natural Yield, we freeze dry our microgreens within hours of harvest to preserve their full nutritional value. Whether fresh or powdered, you can trust that you’re getting maximum nutrition, delivered naturally.
References
Davis et al., 2004. Changes in USDA Nutrient Content Data. HortScience
USDA Nutrient Retention Factors Database
Xiao et al., 2012. Nutritional Comparison of Broccoli Microgreens. J Agric Food Chem
Ratti, C. (2001). Hot air and freeze-drying of high-value foods: A review. Journal of Food Engineering, 49(4), 311-319.
USDA ARS Nutrient Data Laboratory – Database of nutrient retention factors.
Ciurzyńska, A., & Lenart, A. (2011). Freeze-drying – application in food processing and biotechnology. Polish Journal of Food and Nutrition Sciences.
Shofian, N.M. et al. (2011). Effect of drying on the antioxidant activity of selected tropical fruits. International Food Research Journal, 18(3), 1047-1054.
Disclaimer: The information provided in this article is for educational and informational purposes only and is not intended as medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a qualified healthcare provider with any questions you may have regarding a medical condition. The author and publisher of this article are not responsible for any adverse effects or consequences resulting from the use of any suggestions, preparations, or procedures described in this article.