[Desert_Rose (OP)]

Do the enzymes in fruit and vegis survive freezing?  Specifically pineapple, orange, lemon?

On another thread I got a recipe for these, but I would need to buy 2 pineapples, 1 1/2 to cut and serve, the other 1/2 for recipe.

thanks
Joanne

[Desert_Rose (OP)]

I know cooking destroys enzymes, does freezing?
Joanne

[another_someone]

Cooking denatures proteins, I've not heard before that freezing does this.

Since it has been possible to freeze human eggs, and still use them afterwards (albeit, there remains a risk of damage in the process), it would indicate that it is possible to freeze and thaw all the metabolic processes (including proteins and enzymes) without causing them harm.

One big problem unusually with freezing is the creation of ice crystals that can destroy the cell walls.  This means you either need some way to prevent the creation of ice crystals (e.g. the use of glycol), or flash freeze so as not to give ice crystals time to form.

My guess would be that ice crystals would not themselves destroy enzymes, but if the cell structure is destroyed, then it could be that when the fruit is subsequently thawed, other processes within the damaged cell could attack the enzymes (like damaged fruit will rot easily).

[neilep]

http://www.thenakedscientists.com/forum/topic.asp?TOPIC_ID=1542


I don't think this answers the enzyme question but may be of use

Men are the same as women.... just inside out !!

[Desert_Rose (OP)]

Thank you.  I checked it out and I may be able to use it someday.

I have actually found an answer, unfortunatly I don't speak or read "chemistry".  So if you or someone on this fun forum could read it and translate it for me in "lay terms", I would be so appreciative...its chapter is titled "Factors affecting Enzyme Action."  

users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Enzymes.html

Thanks again
Joanne

[another_someone]

quote:Originally posted by Desert_Rose

Thank you.  I checked it out and I may be able to use it someday.

I have actually found an answer, unfortunatly I don't speak or read "chemistry".  So if you or someone on this fun forum could read it and translate it for me in "lay terms", I would be so appreciative...its chapter is titled "Factors affecting Enzyme Action."  

users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Enzymes.html

Thanks again
Joanne

Not a chemist, so trying to guess a little at the meaning.

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Enzymes.html#pHandTemp

quote:
The activity of enzymes is strongly affected by changes in pH and temperature. Each enzyme works best at a certain pH (left graph) and temperature (right graph), its activity decreasing at values above and below that point.

Says that enzyme action is dependent upon temperature, but not that enzymes are destroyed by changes in temperature (i.e. it does not itself talk of permanent damage, only an inhibition of action that may or may not be reversible when temperature reverts to its optimum).

quote:
Hydrogen bonds are easily disrupted by increasing temperature. This, in turn, may disrupt the shape of the enzyme so that its affinity for its substrate diminishes. The ascending portion of the temperature curve (red arrow in right-hand graph above) reflects the general effect of increasing temperature on the rate of chemical reactions (graph at left). The descending portion of the curve above (blue arrow) reflects the loss of catalytic activity as the enzyme molecules become denatured at high temperatures.

This does refer to permanent damage caused by increasing temperature, but does not mention the effect of decreasing temperature.

[Desert_Rose (OP)]

Yeah, that's as far as I got, too, when I read it.  I guess I just really want that other inch of comprehension.

Thanks
Joanne

[Desert_Rose (OP)]

Well, I've searched far & wide!
I did find my answer in easy to understand language, so I withdraw the question.
Joanne

[Desert_Rose (OP)]

Blanching done before freezing seems to be the destroyer of enzymes, not the freezing itself.  That being the point of blanching, as I understand it.