Page 216 - Analytical method for food addtives

144 Analytical methods for food additives

propyl gallate and tert-butylhydroquinone by use of chemometric approaches’, Ni Y,
Wang L, Kokot S. Analytica Chimica Acta (2000) 412, 185–193.
16 ‘Development and comparison of analytical methods for BHA, BHT and PG determi-
nation in foods’, Minim Y P R, Cecchi H M. Ciencia e Tecnologia de Alimentos. (1995)
15(2), 150–154. [Spanish]
17 ‘AOAC Official Method 952.09. Propyl gallate in food, colorimetric method’, AOAC
Official Method of Analysis (2000) 47.2.04 p 6.

11.5 Appendix: method procedure summaries

Analysis of oils, fats and butter oil 1, 2
AOAC official method 983.15, phenolic antioxidants in oils, fats and butter
oil, liquid chromatographic method, IUPAC–AOAC method

Principle
Antioxidants are extracted into acetonitrile. Extract is concentrated and diluted
with 2-propanol. Antioxidants are separated by liquid chromatograph and measured
by ultraviolet detection at 280 nm.

Determination
(a) Extraction – Accurately weigh to nearest 0.01 g 50 mL beaker containing c.
5.5 g liquid or butter oil or c. 3.0 g lard or shortening (liquefied in bulk using
60 °C water bath or oven, and swirled or shaken to ensure homogeneity).
Decant as much test portion as possible into 125 mL separatory funnel
containing 20 mL (22.5 mL for lard or shortening) saturated hexane. Reweigh
beaker to determine test portion weight. Swirl to mix test portion with hexane,
and extract with three 50 mL portions of saturated acetonitrile. If emulsions
form, hold separatory funnel under hot tap water 5–10 s. Collect extracts in
250 mL separatory funnel and let combined extracts drain slowly into 250 or
500 mL round-bottom flask to aid removal of hexane-oil droplets. (Note: at
this point, 150 mL acetonitrile extract may be stored overnight, refrigerated.)
Evaporate to 3–4 mL, using flash evaporator with ≤40 °C water bath, within
10 min. (Note: (1) Prolonged evaporation time may cause TBHQ losses. To
decrease evaporation time, use efficient vacuum source and water-ice con-
denser cooling. (2) Use 500 mL flask to reduce ‘bumping’ losses. Take care to
ensure quantitative transfer of extract after evaporation.) Using disposable
pipette, transfer acetonitrile-oil droplet mixture to 10 mL glass-stoppered
graduated cylinder. Rinse flask with small portions non-saturated acetonitrile.
As rinse pools in flask bottom, pipette rinse to cylinder until 5 mL is collected.
Rinse pipette through top and continue to rinse flask with small portions 2-
propanol, transferring rinses to cylinder until 10 mL is collected. Mix cylinder
contents. (Note: delay in analysing extracted test portion may cause TBHQ
loss.)