Updated: Dec 25, 2020
NULL HYPOTHESIS 7 (Kiwi): Blanching Kiwifruit for 90 seconds before freeze-drying will not affect taste compared to uncooked
Conclusion: We Rejected this Hypothesis
Abstract: We blanched one batch of kiwifruit and left another batch raw. We froze both and then freeze-dried them. Our test subjects tried the raw freeze-dried kiwi and the blanched freeze-dried kiwi. All three of our testers could tell a difference in taste between them. Although not relevant, two of the three preferred the non-blanched kiwi.
Appx. 12 - fresh kiwifruits
1 Harvest Right freeze dryer tray with a silicone mat
Pot for steaming kiwifruit
1 qt. water
Bowl of ice
Above: The top photo is unblanched kiwifruit before freeze-drying. The bottom photo was blanched.
Boil the water in the pan.
Put half the kiwifruit in the boiling water for 90 seconds.
Drain water off kiwifruit and place kiwi in the ice.
When cold, lay the kiwifruit out on the tray.
Lay the unblanched kiwifruit out on the other tray.
Freeze both trays overnight.
Start freeze drier to the non-liquid, pre-freeze setting (wait 30 mins.)
Once the pre-freeze cycle completes, place the frozen trays in freeze-drier (with 2 other trays of food; we did Oreos, and ice cream sandwiches)
Started the freeze-drying cycle.
Removed kiwifruit from freeze-dryer
Our actual total starting weight of frozen unblanched kiwifruit on the tray was .374 kg and the finished weight was .07 kg (not including the tray itself). Our actual total starting weight of frozen blanched kiwifruit on the tray was .399 kg and the finished weight was .06 kg (not including the tray itself).
The freeze-drier completed its ordinary cycle at 18 hours. We added 5 hours so it wouldn't finish in the middle of the night. The temperature scanner showed an approximate average temperature of 90° F. We did not find any cold spots.
In the photo below, the kiwifruit was blanched before being freeze-dried.
In the photo below, the kiwifruit was not blanched before being freeze-dried.
When I compare them, I see brighter green in the unblanched kiwifruit.
We had each tester try both without knowing which kiwifruit was which. All three testers thought they tasted different so we could reject our hypothesis with this test. Although not relevant, two of the three preferred the non-blanched kiwi.
If we redid this test, we'd shorten the blanching time. We almost didn't complete the experiment because the blanched kiwifruit tasted so bad before freeze-drying it. Once freeze-dried, the blanched kiwifruit tasted much crunchier but didn't really taste like kiwifruit. It also looked off color. I wonder if he shortened the blanch time to 30 seconds if we'd have better results.