DETERMINATION OF FAT IN OLESTRA-CONTAINING SAVORY SNACK PRODUCTS BY CAPILLARY GAS-CHROMATOGRAPHY

A quantitative method to determine fat in olestra-containing savory sn ack products was validated within the AOAC Peer-Verified Methods Progr am. The method may be used to demonstrate compliance with the guidelin es of the U.S. Nutrition Labeling and Education Act for labeling produ cts as ''fat free'' or ''low fat.''. The method can measure total and saturated fat in savory snacks when present at levels of 0.2-10 g tota l fat and 0.1-3 g saturated fat per 30 g serving. The method is standa rdized to measure C-6- C-24 fatty acids. Extraction of olestra-contain ing savory snack samples with chloroform-methanol (modified AOAC Offic ial Method 983.23) yields a lipid extract containing the total fat and olestra. The extracted lipid is hydrolyzed by lipase, yielding fatty acids and unreacted olestra The fatty acids are precipitated as calciu m soaps. Olestra is extracted from insoluble soaps with hexane and the n discarded. The isolated soaps are converted back into fatty acids wi th hydrochloric acid and extracted with hexane. The isolated fatty aci ds are converted to methyl esters with boron trifluoride-methanol and quantitated by capillary gas chromatography using internal standard. T est samples were prepared by blending olestra-containing and full-fat (triglyceride) snacks to obtain 6 levels of spiking (0-10 g total fat added/30 g serving) in potato chips, potato crisps, cheese puffs, and nacho cheese-flavored corn chips. Results were linear (r(2) > 0.997) b etween 0 and 10 g fat/30 g serving for each product matrix. Mean recov ery was 101 +/- 6% standard deviation(SD)for total fat and 104 +/- 6% SD for saturated fat Mean recovery by peer laboratory was 88 +/- 5% SD for total fat and 95 +/- 4% SD for saturated fat in potato chips (0-3 g total fat added/30 g serving). Two sets of 10 replicates of potato chips (0.5 g total fat/30 g serving and 0.16 g saturated fat/30 g serv ing) and potato crisps (0.5 g total fat/30 g serving and 0.16 g satura ted fat/30 g serving) were analyzed by submitting and peer laboratorie s. Repeatability relative standard deviations ranged from 3.90 to 7.33 % for total fat and hem 4.01 to 11.53% for saturated fat Reproducibili ty relative standard deviations were 7.33% (total fat, potato chips), 7. 15%(total fat,potato crisps), 11.36% (saturated fat,potato chips), and 13.50% (saturated fat,potato crisps).