Sample preparation for the analysis of flavors and off-flavors in foods

Department of Health and Human Services, Food and Drug Administration, National Center for Toxicological Research, Jefferson, AR 72079, USA.
Journal of Chromatography A (Impact Factor: 4.17). 07/2000; 880(1-2):3-33. DOI: 10.1016/S0021-9673(00)00318-6
Source: PubMed

ABSTRACT Off-flavors in foods may originate from environmental pollutants, the growth of microorganisms, oxidation of lipids, or endogenous enzymatic decomposition in the foods. The chromatographic analysis of flavors and off-flavors in foods usually requires that the samples first be processed to remove as many interfering compounds as possible. For analysis of foods by gas chromatography (GC), sample preparation may include mincing, homogenation, centrifugation, distillation, simple solvent extraction, supercritical fluid extraction, pressurized-fluid extraction, microwave-assisted extraction, Soxhlet extraction, or methylation. For high-performance liquid chromatography of amines in fish, cheese, sausage and olive oil or aldehydes in fruit juice, sample preparation may include solvent extraction and derivatization. Headspace GC analysis of orange juice, fish, dehydrated potatoes, and milk requires almost no sample preparation. Purge-and-trap GC analysis of dairy products, seafoods, and garlic may require heating, microwave-mediated distillation, purging the sample with inert gases and trapping the analytes with Tenax or C18, thermal desorption, cryofocusing, or elution with ethyl acetate. Solid-phase microextraction GC analysis of spices, milk and fish can involve microwave-mediated distillation, and usually requires adsorption on poly(dimethyl)siloxane or electrodeposition on fibers followed by thermal desorption. For short-path thermal desorption GC analysis of spices, herbs, coffee, peanuts, candy, mushrooms, beverages, olive oil, honey, and milk, samples are placed in a glass-lined stainless steel thermal desorption tube, which is purged with helium and then heated gradually to desorb the volatiles for analysis. Few of the methods that are available for analysis of food flavors and off-flavors can be described simultaneously as cheap, easy and good.

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    • "Comparing Tables 2 and 3 shows that 2-deca- none and 2-undecanone were only detected in skim milk, and 2-heptanone, 2-octanone and 2-no- nanone were detected in higher amounts in skim milk as compared with NSTD milk. These differences may, at least partially, be due a protective effect of the milk fat against release of volatile compounds from the NSTD milk during the dynamic headspace sampling (Wilkes et al. 2000). The content of 2-propanone and 2-butanone in both skim milk and NSTD milk was significantly higher in the reference samples (raw milk, HTST and 85°C ⁄ 30 s pasteurised milk) than in the samples subjected to IIP (Tables 2 and 3). "
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    ABSTRACT: Volatile compounds in skim milk and nonstandardised milk subjected to instant infusion pasteurisation at 80°C, 100°C and 120°C were compared with raw milk, high temperature short time pasteurised milk and milk pasteurised at 85°C/30 s. The composition of volatile compounds differed between infusion pasteurisation treated samples and the reference pasteurisations. The sensory properties of skim milk subjected to instant infusion pasteurisation were described by negative attributes, such as cardboard sour and plastic flavours, which are not associated normally with fresh milk. Partial least squares modelling showed good correlation between the volatile compounds and the sensory properties, indicating the predictive and possible causal importance of the volatile compounds for the sensory characteristics.
    International Journal of Dairy Technology 01/2011; 64(1):34 - 44. DOI:10.1111/j.1471-0307.2010.00641.x · 0.94 Impact Factor
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    • "The sensory characteristics of a compound fragrant and in particular the threshold of perception can change depending on whether one is alone or in combination with other volatile compounds (Buettner & Schieberle, 2000). Several techniques were used for the sampling of flavors in foods products (Wilkes et al., 2000), among them, the pre-concentration of volatile compounds by solid-phase microextraction in headspace mode (HS-SPME) was a solvent free, simple, rapid and reliable method that does not induce modifications of volatile compounds due to temperature or solvent effect (Holt, 2001; Kataoka, Lord, & Pawlisyn, 2000; Zhang, Yang, & Pawlisyn, 1994). SPME directly coupled with GC and/or GC/MS was used for the analysis of odours, such as tomato, apricot, pear, peach, strawberry and apple ( "
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    ABSTRACT: The volatile compounds of Citrus juices have been extracted by headspace solid-phase microextraction (HS-SPME) and analysed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). This work deals with the analysis of 65 cross pollinated hybrid fruits and their parents: mandarin (Citrus reticulata Blanco var. Willow Leaf) and clementine (Citrus reticulata×Citrus sinensis var. Commune). Among the 44 components identified which accounted for 90.2 to 99.8% of the volatile fraction, limonene (56.8–93.3%) and γ-terpinene (0.1–36.4%) were the major components in all samples. The clementine juice was characterised by the pre-eminence of limonene (90.0%) and a minor amount of γ-terpinene (1.2%) while the mandarin juice exhibited high amount of limonene (66.3%) and γ-terpinene (21.1%). All hybrid juices showed qualitatively similar composition but differing in the quantitative profile of the couple limonene/γ-terpinene. The principal component analysis (PCA) and the discriminant analysis indicated that hybrids samples were symmetrically distributed around the both parents. If some studies were found in the literature about mandarin juice, to our knowledge, this work is the first study on the volatile compounds of clementine juice and a large amount of hybrids.
    Food Chemistry 09/2009; 116(1):382-390. DOI:10.1016/j.foodchem.2009.02.031 · 3.39 Impact Factor
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    • "In the making of Swiss cheese, correlations have been shown between the abundance of Enterococcus spp. in milk and tyramine in cheese; between L. casei in milk and histamine in cheese, and between coliforms in milk and diamines in cheese. In cream-filled hazelnut cakes, the osmotolerant spoilage yeast Hansenula anomala (=Pichia anomala) may produce an offflavor due to ethyl acetate (Wilkes et al., 2000). α-Dicarbonyls, particularly methyl-glyoxal and diacetyl, and bacteria which can produce them, appear to play a crucial role in the formation of cheese flavour, both the desirable flavour of full-fat cheese and the meaty-brothy off-flavour of low-fat cheese (Urbach, 1995). "
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    ABSTRACT: Milk and milk products are an important part of daily nutrition in many regions of the world. Besides fulfilling nutritional requirements, the flavour of milk and milk products is a key parameter for consumer acceptance and marketing (Drake et al., 2007a). The market for dairy products in more traditional dairying countries has been growing steadily; most of this growth can be attributed directly to the introduction of novel product options and increasing application of milk constituents in other food formulations. Due to the importance of dairy products in daily life, especially for consumers in traditional dairying countries, they are being used increasingly as delivery systems for biologically active/nutraceutical preparations. Even higher growth in the consumption of milk and milk products is now coming from countries which did not have any tradition of dairying; such countries offer tremendous opportunity for further enhanced sales. At the same time this increased consumption also challenges researchers and manufacturers to create new product solutions to better suit the palette of consumers recently introduced to dairy products.
    Advanced Dairy Chemistry, 04/2009: pages 631-690;
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