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Blanching Broccoli

Updated: Dec 25, 2020

NULL HYPOTHESIS 1 (Broccoli): Blanching before freeze-drying will not affect taste compared to uncooked

Conclusion: Cannot Reject the Hypothesis

Abstract: We blanched one batch of broccoli and left one batch raw. We froze both and then freeze-dried them. Our test subjects tried the raw freeze-dried broccoli and the blanched freeze-dried broccoli. First, our three test subjects ate the freeze-dried broccoli without rehydrating it. Two of the three thought it tasted the same. Second, our three test subjects tried the broccoli after we rehydrated it and microwaved it. Again, two of the three thought they tasted the same.

Starting Materials:

  • Appx. 1.5 lbs. - store-bought, flash-frozen broccoli

  • 1 Harvest Right freeze dryer tray with a silicone mat

  • Pot for steaming broccoli

  • 1/2 cup water


  1. Spread frozen broccoli out on the silicone mat in the tray, one layer deep.

  2. Put the tray in the freezer.

  3. Boil the water in the pan.

  4. Put half the frozen broccoli in the boiling water for 3 minutes.

  5. Drain water off frozen broccoli and return the broccoli to the tray.

  6. Place the tray in the freezer until blanched broccoli is refrozen.

  7. Started freeze drier to the non-liquid, pre-freeze setting (waited 30 mins.)

  8. Once the pre-freeze cycle complete, place the frozen tray of broccoli in freeze-drier (with 3 other trays of food; we did scrambled eggs, cooked black beans, and pork carnitas)

  9. Started the freeze-drying cycle.

  10. Removed broccoli from freeze-dryer

  11. Taste-tested broccoli without rehydrating.

  12. Rehydrated broccoli in tap water for two minutes, then microwaved for 1 min.

  13. Taste-tested rehydrated broccoli.

Our actual total starting weight of frozen broccoli on the tray was 1 lb. 9 oz. (not including the tray itself). We measured by determining how much could be spread out in a single layer on the tray rather than by weight. Our total finished dried weight was __ oz.


The freeze-drier completed its ordinary cycle at 29 hours. The temperature scanner showed an approximate average temperature of 82° F (we use an infrared food thermometer to scan finished trays of food to try and determine if there are ice crystals that measure as cold spots). We did not find any cold spots.

In the photo below, the broccoli on the left is raw and freeze-dried. The broccoli on the right was blanched and then freeze-dried. When I compare them, I see brighter green in the raw broccoli. They are nearly indistinguishable.

Each of our subjects (my wife and two kids), looked at the plates of broccoli below to compare their visual appearance. One tester thought the raw broccoli looked better and the other two thought they looked the same.

The first plate is raw. The second plate was blanched before freeze-drying.

In our first taste test, we had each tester try both without knowing which broccoli was which. Two testers thought they tasted the same and one tester thought the blanched broccoli tasted better. Unlike with typical broccoli, my testers cheated and almost ate it all before the second test.

In our second test, we rehydrated the broccoli for two minutes in filtered tap water. They we put each batch into the microwave for one minute. Two testers again thought they tasted the same. One tester again thought the blanched broccoli tasted better.

More importantly, my kids ate broccoli and it wasn't dinner time.

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