Dynamic Headspace Concentration and Gas Chromatography of Volatile Flavor Components in Peach

Dynamic headspace concentration was used to trap peach flavor volatiles from a promising cultivar under development. Separation and identification of components were by high resolution gas chromatography and mass spectrometry. One hundred ten compounds including alcohols, aldehydes, alkanes, esters, ketones, aromatic hydrocarbons, sulfur-containing compounds and some miscellaneous compounds were positively or tentatively identified. Forty-six compounds were positively identified in peach for the first time.     

大型荧幕作业下工作绩效与视觉不适之研究

伴随今日荧幕技术进步,大型荧幕已经成为一种流行趋势.本研究希望得知大型荧幕对视觉、工作绩效之影响,并了解肌肉不适之情形.比较四种荧幕尺寸(15、17、19和21英时)以主观评量、工作绩效、视觉压力、颈肩姿势与肌肉活动之影响.由主观评量得知,19时工作绩效是最好的,荧幕大小对视觉表面积的影响是显著的,在工作超过一小时候,眨眼率与视觉疲劳也大幅增加,颈肩姿势对荧幕大小无显著的,最后,荧幕大小对平均作业时间有显著的影响.结论,19 英时萤幕是我们推荐适用于长时间的作业平台.     

Texture Changes of Frozen Stored Cod and Ocean Perch Minces

During frozen storage, minced cod and ocean perch were examined by expressible moisture (EM), water binding potential (WBP) and computerized texture profile analysis (TPA). The results suggested that a microcomputer interfaced with the Instron efficiently performed TPA. The texture and water loss of all fish minces changed more rapidly at -7°C storage than at -20°C and -40°C. Furthermore, cod, a gadoid with the ability to degrade trimethylamine oxide to dimethylamine and formaldehyde, deteriorated faster than ocean perch, which did not have this ability. EM was useful for examining the water loss of frozen fish at - 7°C only during the first two weeks of storage. The WBP at -7°C storage showed a good correlation with storage time for cod and ocean perch. This suggests that WBP might be a good indicator for examining water holding ability of fish proteins.     

SPECIES SUBSTITUTION OF RETAIL SNAPPER FILLETS

A total of 121 retail market snapper fillets were collected throughout Florida and tested for compliance with labeling regulations. Samples were identified as to species by isoelectric focusing techniques against 12 authentic snapper species. Of the 81 red snapper samples, 24 (30%) were confirmed as real red snapper (Lutjanus campechanus), while 57 (70%) were mislabeled. Most of the other snapper species were correctly labeled. The major substitute for red snapper was scarlet snapper (Lutjanus sanguineus), an imported red-skin Pacific snapper species. Nomenclature of fish sold in the market is confusing since the same species of fish is frequently sold by several different names.     

Volatile Flavor Components in Crayfish Waste

Volatile components of crayfish processing waste were analyzed by dynamic headspace/capillary gas chromatography/mass spectrometry and chromatography-coupled aroma perception analysis with simultaneous photoionization detection. One hundred seventeen compounds were identified. The majority of the flavor compounds previously identified in freshly boiled crayfish tail meat and hepatopancreas also were detected in crayfish waste. Many areas in the headspace profile contained good nutty, green woody, sweet fruity and very desirable salty meaty aromas, indicating the presence of important crayfish flavor components in the sample.     

Volatile Compounds in Scrambled Eggs

Volatile compounds in scrambled eggs were analyzed by dynamic headspace sampling, high resolution gas chromatography and mass spectrometry. Thirty-eight compounds were identified including aldehydes, ketones, alcohols, furans, esters, benzene derivatives, alkancs, sulfur-containing compounds and a terpene. Selected compounds were quantified. Aldehydes were the most abundant volatile compounds in the egg samples. Volatile styrene monomer increased in scrambled egg samples during 2 wk storage of shell eggs in polystyrene containers. Scrambled eggs prepared from supermarket shell eggs contained 7 times more ethylbenzene and styrene than those prepared from fresh farm eggs stored in polystyrene containers for 2 wk.     

Methodology for Quantification of Geosmin and Levels in Rangia Clam (Rangia cuneata)

The concentration of geosmin was determined in freshly dredged and 2-wk relayed rangia clam (Rangia cuneata) samples in different seasons of the year. Vacuum distillation/solvent extraction using an internal standard was followed by multiple-level standard addition gas chromatography/selective ion monitoring mass spectrometry. Most coefficients of variation were lower than 10%. On a dry-weight basis, the geosmin level in dredged clams was highest (343 ng/g) in August and averaged 51.6 ng/g in other months. A 52% reduction of geosmin was found after two week relaying during the period of May-June. However, only 1% reduction of geosmin was observed during February-March.     

A simple criterion for global stabilizability of a class of nonlinear singularly perturbed systems

In this paper, a simple criterion is proposed for the global stabilizability of a class of nonlinear singularly perturbed systems. Our approach is based on the global nonlinear controller canonical transformation and the integral manifold method. A globally stabilizing feedback control is also proposed such that the pre-specified design manifold becomes an exact slow integral manifold and the trajectories of the closed-loop system, starting from any initial states, are steered along the integral manifold to the origin.