From: sbhattac@sales.GBA.NYU.EDU (Shankar Bhattacharyya)
Newsgroups: rec.food.cooking
Subject: Re: Shortening (was Re: rec.food.cooking)
Date: 8 Apr 92 01:33:08 GMT
Organization: NYU Stern School of Business

In article <1992Apr06.133653.28504@bmerh2.bnr.ca> stu1f12@bnr.ca (Dave Malecki) writes:

>My father has been watching his cholesterol for a while now (no butter in the
>house any more :( ) so my parents have been using soya margarine.  From what
>has been going on on the net, it would seem that in order for a margerine to 
>be solid, the soya oil must be hydrogenated (says so on the tub).  This 
>saturates the fat making it worse from a cholersterol point.  Would it be 
>better to paint your bread with oil then?  What about olive oil?  I have 
>heard so many good things about it, yet it hardens in the fridge.  This
>would indicate to me that it is higher in saturated fats than other oils.
>Could someone explain this anomaly?

I'll nibble at the subject, but don't expect categorical answers.

Also, I have absolutely no comment on the health issues. No qualifications
for comments on health issues either. I don't even imply anything about
those issues.

Yes, hydrogenation increases the degree of saturation. Or, to be more
precise, and to ensure that other chemists do not nail me to the wall for
odd usage, hydrogenation reduces the degree of unsaturation.

However, margarines are not completely saturated. In general, not by a long
shot. They tend to be not wildly away from monounsaturated on average.

Vegetable fats contain a range of fatty acids, some saturated, some
monounsaturated, some doubly unsaturated, some triply unsaturated. More
unsaturated fats are pretty much undetectable in edible vegetable fats.

During hydrogenation, on average, the more unsaturated fats react faster.
There tends to be a buildup of the monounsaturated fats.

There are three major factors involved in whether fats are solid or liquid.

The first is the degree of saturation. Saturated fats have higher melting
points than do unsaturated fats. Since fats are mixtures of many substances,
this is a continuous effect.

The second is the average length of the fatty acid chain. Palm oils have
rather rather a lot of the shorter fatty acids. Indeed, this is a large
part of the reason they are so unambiguously solid at quite modestly cool
temperatures. Not to say that they are not pretty much saturated, but the
consensus among us food nerds is that the melting point of palm oils is
more a matter of chain length than of saturation. That does not alter the
fact that they are ghastly fats, very nearly saturated. They are also very
heterogeneous, which leads to some quite odd melting point behaviour.

The third factor is an issue not for moisture-free fats, but for such
things as margarines, which contain quite a lot of water. Margarine is an
emulsion, i.e. a colloidal suspension of one liquid in another. In such an
emulsion, if there is a lot more of one liquid than the other, the whole
behaves pretty much like a liquid. As quantities approach some range of
ratios in the neighbourhood of 1:1 (and I make no suggestion that 1:1 is
special; it depends), the emulsions start to behave like creams. Note that a
vinaigrette is fairly creamy, even though its components are quite clearly
liquids.

If you make the emulsion more stable, and can adjust the conditions so that
the droplets are smaller, the emulsion can behave very much like a waxy
solid. That's what the lecithin and other emulsifiers in margarine are for.

So the fact that margarine seems solid can be misleading. How unsaturated
it is is *NOT* obvious from just that. If you want information on that
sort of thing, call the company and ask them for the fatty acid
composition. That may actually be on the label, too. If you need help
deciphering the information, send me e-mail. Companies will provide you
with details if you make a little noise. If you make enough noise they will
give you a detailed fatty acid profile, but that may not be very useful to
most people, and the non-technical types at the company won't even know
what you are asking for.

A couple of things to keep in mind:

Brushing oil on seems like an attractive idea, but oil will soak in, and
you may wind up using vastly more fat than you would dispense on the end
of a knife. Quantity matters, too.

Finally, hydrogenated fats which have not been hydrogenated all the way, as
is the case for margarines, tend to have rather a lot of trans fatty acids,
as against the natural cis acids. There is growing concern about this. I
express no opinion on that subject.

- Shankar