67C-24 |
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A. SCHIEBER1, R. Fuegel, and R. Carle. (1) Institute of Food Technology, Hohenheim University, August-von-Hartmann-Strasse 3, Stuttgart, 70599, Germany Adulteration of food is a serious economic problem, and blending of fruit-based products such as jams, purees and fruit preparations with cheaper fruits has frequently been reported. The problem is further aggravated by the lack of methods for the determination of the specified fruit content. Low molecular compounds (sugars, amino acids etc.) and minerals are not reliable for this purpose since these parameters can easily be manipulated. The objective of our study was to investigate cell wall polysaccharides for their suitability as markers for quality and authenticity control of fruit products. The alcohol-insoluble residues (AIR) of strawberry, cherry, and apple fruits were fractionated into water-, oxalate-, acid-, and alkali-insoluble pectins, hemicellulose and cellulose. After acidic hydrolysis the neutral sugars of each fraction were determined by capillary electrophoresis. Strawberry fruit preparations with fruit contents ranging between 30 and 60 % were produced using various starches, pectin and xanthan as thickening agents. For the determination of the fruit content, added hydrocolloids were enzymatically degraded and residual fruit preparations were subjected to the fractionation described above. Finally, the hemicellulose fraction was quantified gravimetrically. Characteristic neutral sugar profiles of the AIR were found which may be used for the differentiation of fruit species in products. The isolated hemicellulose fraction not only displayed a fruit-specific neutral sugar fingerprint, but also proved to be suitable for the quantification of the fruit content of strawberry fruit preparations, showing excellent agreement between specified and determined contents (30 vs. 31.5 %; 45 vs. 44.7 %; 60 vs. 64.0 %). This novel method is considerably more reliable than those based on low molecular compounds which can easily be added to feign a higher fruit content. Hemicellulose as a high molecular marker is much less susceptible to adulterations and is not affected by food ingredients usually added to fruit preparations.
Session 67C, Food Chemistry: Food analysis, irradiation and toxicology
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