Sir:
Previous reports from our laboratory described the physical
properties of soybean oils high in saturated acids (1), and
other published work indicated that these oils have potential
uses in soft margarine formulations, either by blending with
harder components and/or interesterification of their glyceride
structures (1,2). A recent publication by Kok et al. (3) de-
scribed formulation of soft margarines from interesterified
soybean oils high in both palmitic and stearic acids. We wish
to describe some properties of soft margarine prepared from
soybean oils from the HS-1 cultivar developed by the Hartz
Seed Company (Stuttgart, AR) (4). Three separate lots of
HS-1 showed stearic acid contents ranging from 16–21%,
palmitic acid from 9–10%, oleic acid from 19–22%, linoleic
acid from 42–44%, and linolenic acid from 4–6%; dropping
points ranging from about 15–17°C; and typical solid fat
indexes (SFI) of 8–10 at 10°C and essentially zero at
21.1–33.3°C. After random interesterification of the neat
HS-1, as described previously (1,5), dropping points (6) in-
creased to 34–36°C and SFI (5) values ranged from 5–8 at
10°C, 2–3 at 21.1°C, and 1–2 at 33.3°C.
Soft margarine was formulated in the laboratory from an
emulsion prepared from 8,010 g interesterified HS-1 or hy-
drogenated soybean oil, 1,970 g skim milk, 10 g fluid lecithin,
20 g mono/diglycerides, 10 g salt, and 0.003% β-carotene.
The emulsion, at 40°C, was pumped from an air-driven im-
peller-agitated tank to an Armfield (Armfield, Inc., Denison,
IA) scraped surface heat exchanger (model FT 25B) at a rate
of 6 L/h. The brine temperature controlling the “A” unit was
0°C. The “A” unit, or crystallizer, was operated at 400 rpm as
was the “B” unit (pin worker). Product pressure was 4 psi.
Controls were prepared from a commercially blended, hydro-
genated, liquid soybean oil blend having a dropping point of
32°C and SFI values of 11–13 at 10°C, 4–5 at 21.1°C, and
1–2 at 33.3°C. Temperatures were monitored throughout the
formulations and were as follows: temperature of emulsion
into the “A” unit or scraped surface unit 32°C, out of the “A”
unit to the “B” unit or pin worker 9–11°C, out of the “B” unit
9.5–11°C. Products emerging from the pin worker were
placed in 8-oz plastic tubs, placed in a refrigerator held at
45°F (7.2°C), and held for 12 h prior to testing. The experi-
mental margarines were evaluated by a trained sensory panel
consisting of 10 members. Panelists were asked to rate the
products for spreadability (0 = easy to spread, 10 = hard to
spread) by spreading a 4-g sample onto small bread squares
with a plastic knife. Mouth melt was determined by measur-
ing the time, in seconds, necessary for a 2-g sample to melt in
the mouth. Panelists were asked to rate the sample for graini-
ness or texture on a 10-point scale (0 = smooth, 10 = gritty).
Other tests included softness or penetration by the American
Oil Chemists’ Society official method and an oil-off test
where a 25-g sample is stored for 4 d at 70°F (21.1°C) on a
wire screen and the amount of water or oil lost from the emul-
sion is noted (7). In addition to the experimental margarines
formulated in the laboratory from HS-1 and hydrogenated
soybean oil, two commercial margarines (80% fat) purchased
from a local supermarket were evaluated. These products
were formulated from blends of hydrogenated and liquid soy-
bean oils having SFI profiles and dropping points nearly iden-
tical to that used in the laboratory formulations. The proper-
ties of the experimental and commercial margarines are
shown in Table 1. Margarines formulated in the laboratory
from hydrogenated soybean showed penetration values rang-
ing from 136–185 depending on the speed (rpm) of the pin
worker or “B” unit with the softest products obtained at the
highest rpm. By contrast, the margarine from interesterified
HS-1 had penetrations of 75–92, indicating a harder product.
The commercial margarines, which are softer than the inter-
esterified margarines, but harder than the hydrogenated prod-
ucts prepared in the laboratory, showed penetrations of
104–137. Spreadability, as determined by the sensory panel,
was plotted against penetration values and the results are
shown in Figure 1. A significant correlation (r = 0.814) was
found. The HS-1 margarines showed spreadability values of
over 6 compared to 3–5 found for commercial samples. How-
ever, the HS-1 samples were spreadable directly out of the re-
frigerator. Sensory evaluations showed that little or no graini-
ness was detected in either the commercial or interesterified
margarines. Mouth-melt data indicate that the interesterified
products are comparable to commercial products. Oil-off tests
showed that interesterified products perform as well as the
commercial products since no water loss occurred and oil
losses were small in both types of samples. Attempts were
made to induce texture defects in the experimental margarines
by removing them from the refrigerator and allowing them to
stand at room temperature (70°F) for 2 h. They were placed
back in the refrigerator for 12 h. This procedure was repeated
four additional times for a total of five cycles. Results showed
that no visible texture defects occurred, nor was any increase
in graininess detected by the sensory panel. No significant in-
Copyright © 2001 by AOCS Press 103 JAOCS, Vol. 78, no. 1 (2001)
Paper no. J9770 in JAOCS 78, 103–104 (January 2001).
1
Presented in part at the 90th American Oil Chemists’ Society Annual Meet-
ing & Expo in Orlando, FL, May, 1999.
LETTERS TO THE EDITOR
Soft Margarines from High Stearic Acid Soybean Oils
1