title: Application of Fourier transform infrared spectroscopy for monitoring short-chain free fatty acids in Swiss cheese.
abstract: Short-chain free fatty acids (FFA) are important sources of cheese flavor and have been reported to be indicators for assessing quality. The objective of this research was to develop a simple and rapid screening tool for monitoring the short-chain FFA contents in Swiss cheese by using Fourier transform infrared spectroscopy (FTIR). Forty-four Swiss cheese samples were evaluated by using a MIRacle three-reflection diamond attenuated total reflectance (ATR) accessory. Two different sampling techniques were used for FTIR/ATR measurement: direct measurement of Swiss cheese slices (approximately 0.5 g) and measurement of a water-soluble fraction of cheese. The amounts of FFA (propionic, acetic, and butyric acids) in the water-soluble fraction of samples were analyzed by gas chromatography-flame ion-ization detection as a reference method. Calibration models for both direct measurement and the water-soluble fraction of cheese were developed based on a cross-validated (leave-one-out approach) partial least squares regression by using the regions of 3,000 to 2,800, 1,775 to 1,680, and 1,500 to 900 cm(-1) for short-chain FFA in cheese. Promising performance statistics were obtained for the calibration models of both direct measurement and the water-soluble fraction, with improved performance statistics obtained from the water-soluble extract, particularly for propionic acid. Partial least squares models generated from FTIR/ATR spectra by direct measurement of cheeses gave standard errors of cross-validation of 9.7 mg/100 g of cheese for propionic acid, 9.3 mg/100 g of cheese for acetic acid, and 5.5 mg/100 g of cheese for butyric acid, and correlation coefficients >0.9. Standard error of cross-validation values for the water-soluble fraction were 4.4 mg/100 g of cheese for propionic acid, 9.2 mg/100 g of cheese for acetic acid, and 5.2 mg/100 g of cheese for butyric acid with correlation coefficients of 0.98, 0.95, and 0.92, respectively. Infrared spectroscopy and chemometrics accurately and precisely predicted the short-chain FFA content in Swiss cheeses and in the water-soluble fraction of the cheese.
authors.affiliation: Department of Food Science and Technology, The Ohio State University, 110 Parker Food Science and Technology Building, 2015 Fyffe Rd., Columbus 43210, USA.
authors.forename: N
authors.initials: N
authors.lastname: Koca
authors.forename: L E
authors.initials: LE
authors.lastname: Rodriguez-Saona
authors.forename: W J
authors.initials: WJ
authors.lastname: Harper
authors.forename: V B
authors.initials: VB
authors.lastname: Alvarez
mesh_terms: D000818:Animals; D002611:Cheese / Q000032:analysis*; D002849:Chromatography, Gas / Q000379:methods; D004041:Dietary Fats / Q000032:analysis; D005230:Fatty Acids, Nonesterified / Q000032:analysis*; D005410:Flame Ionization / Q000379:methods; D005504:Food Analysis / Q000295:instrumentation / Q000379:methods*; D016018:Least-Squares Analysis; D012016:Reference Values; D015203:Reproducibility of Results; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013223:Statistics as Topic
chemical_list: D004041:Dietary Fats; D005230:Fatty Acids, Nonesterified