铜、锌、铁清料法加工溏心皮蛋的比较研究

在用NaOH清料法直接加工皮蛋过程中,采用了CuSO4·5H2O、ZnSO4·7H2O和FeSO4·7H2O三种微量辅料,并对单独或混合使用这些微量辅料加工溏心皮蛋的优劣进行了比较。研究表明,当用NaOH代替Na2CO3和CaO直接加工皮蛋时,“铜法”、“铜锌混合法”和“铁锌混合法”效果最优,“锌法”对加工时间要求严格且效果略次,“铁法”不能成功。     

Age-associated variation in sensory perception of iron in drinking water and the potential for overexposure in the human population

Humans interact with their environment through the five senses, but little is known about population variability in the ability to assess contaminants. Sensory thresholds and biochemical indicators of metallic flavor perception in humans were evaluated for ferrous (Fe(2+)) iron in drinking water; subjects aged 19-84 years participated. Metallic flavor thresholds for individuals and subpopulations based on age were determined. Oral lipid oxidation and oral pH were measured in saliva as potential biochemical indicators. Individual thresholds were 0.007-14.14 mg/L Fe(2+) and the overall population threshold was 0.17 mg/L Fe(2+) in reagent water. Average thresholds for individuals younger and older than 50 years of age (grouped by the daily recommended nutritional guidelines for iron intake) were significantly different (p = 0.013); the population thresholds for each group were 0.045 mg/L Fe(2+) and 0.498 mg/L Fe(2+), respectively. Many subjects >50 and a few subjects <50 years were insensitive to metallic flavor. There was no correlation between age, oral lipid oxidation, and oral pH. Standardized olfactory assessment found poor sensitivity for Fe(2+) corresponded with conditions of mild, moderate, and total anosmia. The findings demonstrate an age-dependent sensitivity to iron indicating as people age they are less sensitive to metallic perception.     

Evaluation of three gas chromatography-olfactometry methods: comparison of odour intensity-concentration relationships of eight volatile compounds with sensory headspace data

Three gas chromatography–olfactometry methods, i.e. dilution analysis, detection frequency method and posterior intensity method, were evaluated for attribution of odour potency to eight volatile compounds at seven concentration levels. Six serial 1:5 dilutions of a solution consisting of 2-butanone, diacetyl, ethyl acetate, 3-methyl-1-butanol, ethyl butyrate, hexanal, 2-heptanone, α-pinene in pentane were analysed by gas chromatography-olfactometry. In addition, sensory odour intensity of sunflower oil solutions of the compounds at eight concentration levels were determined and related to their headspace concentrations. Posterior intensities correlated reasonably well with sensory odour intensities. Detection frequency data were also highly correlated, whereas dilution analysis led to more diverting results. A large variance among subjects was observed. Therefore, a group of assessors is considered a prerequisite for reliable gas chromatography-olfactometry analysis.     

A quality measurement for sensory profile analysis The contribution of extended cross-validation and resampling techniques

The sensory profile measures an interaction between products and subjects. Faced with this complex information, industry needs an operational tool for describing product sensory properties. Thus, the statistical analysis of profile data should yield a sharp and robust product picture. We set up quality criteria, based on extended cross-validation and re-sampling techniques, to quantify the relevance of factorial method results. We target PCA on mean product scores, and several MANOVA models. We used assessor cross-validation and assessor re-sampling to evaluate respectively the impact of each assessor and the impact of the panel make-up on the product results. PCA and simple MANOVA models are highly robust, whereas complex MANOVA models lead to unstable results.     

Anthocyanin,phenolic composition,colour measurement and sensory analysis of BC commercial red wines

This research established a database of analytical values associated with 173 commercial red wines from 7 vintages (1995–2001), 4 varieties (Pinot noir, Merlot, Cabernet Franc, Cabernet Sauvignon) and 13 vineyard locations within BC. Wines were analyzed for sulfur dioxide, pH, titratable acidity, phenolics, tartaric esters, flavonols, as well as copigmented, monomeric, polymeric, and total anthocyanins. Colour was evaluated using colour density, hue, and L, a¹, b¹ and chroma measurements. The sensory astringent qualities were characterized on a subset of 78 wines, using a panel of 12 judges. The panel evaluated the magnitude of the astringency, astringent aftertaste, oakiness and bitterness, as well as 3 astringent sub-qualities (surface roughness, drying, puckering). Data were analyzed by analysis of variance, principle component analyses, and canonical discriminant analyses to track the influence of variety, vintage and vineyard location. Trends were observable despite large variation in winemaking techniques. Red colour, colour density, copigmented, monomeric, polymeric and total anthocyanins were lowest in Pinot noir and highest in Cabernet Sauvignon wines. Younger wines had higher concentrations of copigmented, monomeric, and total anthocyanins than did older wines. Canonical discriminant analysis of the analytical and sensory determinations were successful in distinguishing the wines according to where the grapes were grown.     

Identification of odour-active compounds in ewes' raw milk commercial cheeses with sensory defects

The aim of this work was to identify key odorant compounds associated with main off-flavours (acid, rancid and faecal) and one defect related to the internal appearance (big irregular eyes) in ewes' raw milk commercial cheeses. Cheese samples were submitted to solvent assisted flavour evaporation (SAFE) and odorant compounds were detected by gas chromatography–olfactometry (GC–O). Odour-active compounds detected by GC–O were identified and quantified by gas chromatography–mass spectrometry (GC–MS). Partial least square regression was performed to determine relationships between relative abundances of the odour-active compounds and sensory defects of commercial cheeses. An imbalance in the concentration of short-chain free fatty acids, predominant compounds in all cheese samples, was associated with acid and rancid off-flavour, whereas faecal off-flavour was related to minor compounds such as 4-methylphenol and 3-methyl-1-butanol. No volatile compound could be related to the defect of big irregular eyes.     

A comparison of sensory methods in quality control

Many different types of sensorial methods have been proposed and used to evaluate and control the sensory quality of foods. However, not all of them are suitable for incorporation in to quality control programmes. To simplify comparison a distinction is proposed between methods that can be used to define sensory specifications or to select a product quality standard and those that can be used to check if a product complies with stated requirements. With this approach, the appropriateness and limitations of different methods and their practical applicability, according to their use with or without a previously selected or developed standard (product, mental or written), are discussed.     

Determination of geosmin and 2,4,6-trichloroanisole in white and red Austrian wines by headspace SPME-GC/MS and comparison with sensory analysis

This paper describes the development and application of a fast and simple headspace solid phase microextraction GC–MS method for simultaneous determination of geosmin and 2,4,6-trichloroanisole (2,4,6-TCA), two main contributors to off-flavors in wine. The compounds were adsorbed onto a polydimethoxysiloxane (PDMS) fiber at 35 °C for 40 min without prior equilibration, thermally desorbed and analyzed by GC–MS in the selected ion monitoring mode. The parameters for adsorption onto and desorption from the fiber were optimized. This method was applied to analysis of 118 Austrian white and red wines, which were also characterized by sensory analysis. Geosmin was above the limit of detection (0.5 ng/L) in 110 wines (93%) and additionally quantified (>2 ng/L) in 65 wines (55%). It could be detected in wines of each off-flavor (moldy, corky, damp, musty, rotten, woody, grassy) in concentrations up to 16.7 ng/L and even in 90% of the sensorially faultless wines (up to 6.5 ng/L). On the other hand, 2,4,6-trichloroanisole was detected only in 24 wines (20% of all investigated wines) and above the limit of quantitation (2 ng/L) only in 5 wines (4%) sensorially classified as corky; corky and moldy plus other defects; or faultless in concentrations up to 14.3 ng/L. These results show that geosmin is more prevalent than 2,4,6-TCA and that chemical analysis is required especially when other wine characteristic flavors cover beginning off-flavors.