EXPERIMENTAL PROCEDURES
Chicken fat. Rendered chicken fat was procured from a regional
poultry renderer (Simmons Foods®, Silom Springs, AR). The experiment was
begun within one week of the fat rendering.
Treatment of fat with antimicrobials . An aliquot of chicken fat
was transferred into 90 clean and grease-free plastic cups and treated
with two of the acidulants, 0.5% SBS, 0.5% LA or left untreated
(control). The control consisted of distilled water only. The treatments
were added to attain a 3% added moisture level in fat. All the sample
cups were incubated at 40°C for up to 6 weeks. All subsamples for
oxidative measurements were from the middle of sample cups and were only
chicken fat (not added water) at the various pre-determined time
intervals.
Shelf life study of rendered chicken fat. For the determination
of free fatty acids, (American Oil Chemists’ Society (AOCS) official
method Ca 51-40 was used) 75 ml of hot neutralized alcohol was added to
7.05 gm of well mixed sample in an Erlenmeyer flask followed by 2 ml of
phenolphthalein indicator. Shaking vigorously, the content was titrated
using 0.1% potassium hydroxide (KOH) until the appearance of first
permanent pink color of the same intensity as that of the hot
neutralized alcohol which persisted for at least 30 seconds.
The peroxide value of the fat was determined (AOAC official method
965.33) by adding 30 ml of acetic acid: chloroform (3:2, v/v) to 3 gm of
sample in an Erlenmeyer flask with a glass stopper. After swirling to
dissolve, 1 ml of saturated potassium iodide solution was added and
mixed well. Then, after 1 min, 100 ml of distilled water was added to
stop the reaction. After the addition of 1 ml of starch indicator, the
mixture was titrated with 0.01N sodium thiosulfate under constant
shaking until the blue color disappeared. A blank sample with 30mL of
acetic acid: chloroform and 1.0mL of starch solution was also prepared.
The p-anisidine value (AV) was determined (AOCS official method Cd
18-90) with 0.75 gm of the fat sample transferred into a 25 mL
volumetric flask and dissolved with 25 ml of isooctane. After dissolving
for approximately 4-5 minutes, 5ml of the sample was transferred into an
aluminum foil wrapped test tube followed by the addition of 1ml of
p-anisidine. After 10 minutes reaction time, the sample was measured on
a spectrophotometer at 350 nm. Both the sample (without p-anisidine) and
reactions (with p-anisidine) were read separately.
Statistical analysis . The study was conducted as a completely
randomized design with time interval as the block. A total of 3
replications for each treatment was performed. At each of the10-time
points a duplicate sample was tested. Statistical software (SAS; version
9.2) was used to analyze the data for the effects of treatments and
within the time interval. Means were separated with a pairwise
comparison and considered different at a P of 0.05.