FLAVOR AND AROMA ATTRIBUTES OF RIESLING WINES PRODUCED BY FREEZE CONCENTRATION AND MICROWAVE VACUUM DEHYDRATION

This article describes the production of sweet dessert wines produced using late‐harvest freeze concentration, wine produced from fresh grapes frozen using refrigeration and wine produced from grapes partially dried using microwave vacuum dehydration. The objective was to compare the aroma and flavor attributes of the wines to determine the effect of each method of juice concentration. The replicated wine samples were evaluated by 12 experienced judges, and the wines were analyzed using solid‐phase microextraction. The microextraction detected 28 compounds; however, levels of concentration of these compounds were below published aroma thresholds. Although all the wines were judged as acceptable sweet dessert wines, the judges detected significant differences. The wine made from the dehydrated grapes exhibited lower fresh fruit aroma, higher fusel oils and oxidation, and flavor notes including citrus/grapefruit and acidity were lower.     

SENSORY AND PHYSIO‐CHEMICAL PROPERTIES OF MEMBRANE FILTERED APPLE JUICES1

Shelf‐stable apple juices were prepared using two ceramic and four polymeric tubular membranes of varying pore sizes and evaluated using color matching and triangle tests. Juices from 9 kDa and 20 kDa membranes were different in color and aroma/flavor from the other membranes, the characteristics of which did not differ from each other. A full sensory profile was obtained for experimental juices produced using a 0.02 μm ceramic membrane and from commercial pasteurized apple juice. Experimental juices were prepared from fresh and stored apples with and without ascorbic acid. Twelve judges evaluated color; cooked/caramelized, appley, fruity and green aromas and seven flavor attributes (cooked/caramelized, appley, fruity, green, sweet, sour, astringence). Analysis of variance and principal component analysis revealed that membrane filtered juices lacked the cooked/caramelized aroma and had a green flavor compared with the commercial apple juice. Membrane filtered juices prepared from freshly harvested apples had less appley and fruity aroma and flavor, but were more sour and astringent than juices prepared from stored apples. Ascorbic acid treatment significantly reduced the yellow color and increased the astringence of juices.     

Trying to Do Group Theory with Undergraduates and Computers

This paper discusses the author's efforts to use computers and software as a catalyst for engaging undergraduates in the process of doing mathematics in the context of finite group theory. Examples of questions that have been used to motivate undergraduate research and a classroom case study are presented.     

现实与虚幻之间

1997年初我继续学习历程之前，我决定不再欣赏。而是批判甚至挖掘建筑消极的特性。我不完全成功，但这段经历让我思考一系列的问题：什么是现实？什么是虚拟？假的比真的更好吗？这些问题将我引向对建筑自疑的更高领域，当我看当代的建筑案例时，我开始流连于诚实和欺骗之间。     

Inducing malolactic fermentation in Chardonnay musts and wines using different strains of Oenococcus oeni

Malolactic fermentations (MLF) were induced in a commercially prepared Washington State Chardonnay must to evaluate the influence of timing of inoculation and pre-culture conditions of Oenococcus oeni strains MCW, EQ-54, and WS-8. The must (pH 3.62, 21.5°Brix) was divided into lots and inoculated with Saccharomyces cerevisiae strain CY3079. Strains of O. oeni were pre-cultured by growing in diluted juice or by re-hydration of freeze-dried strains. Bacteria were inoculated into the musts before (Day 0) or after completion of the alcoholic fermentation (Day 22). Yeast populations exceeded 10⁷cfu/mL in all fermentations that proceeded to dryness. However, the viability of most strains of O. oeni quickly declined after inoculation regardless of the timing of inoculation or the strain used. MLF was induced in the wines inoculated with strains EQ-54 and WS-8 but not with MCW, and the rate depended on the time of inoculation. The method used to prepare bacterial starter cultures had no apparent influence on the completion of MLF. Values for volatile acidity were slightly higher (P< 0.05) in wines inoculated with O. oeni before alcoholic fermentation compared with those inoculated after alcoholic fermentation.     

CONTRIBUTION OF GLYCEROL, ETHANOL AND SUGAR TO THE PERCEPTION OF VISCOSITY AND DENSITY ELICITED BY MODEL WHITE WINES

The contribution of glycerol, ethanol and sugar to the perception of viscosity and density of model wine (MW) solutions was examined. In study 1, the effects of individual components on perceived viscosity (PV) and perceived density (PD) were studied using 5, 20 or 50 g/L glycerol; 3, 7 or 15% v/v ethanol and 0, 80, 150 or 250 g/L sugar concentrations. In study 2, model ice wine mixtures of 8, 10 or 12% ethanol and 150, 250 or 300 g/L sugar were assessed for PV and PD. The physical viscosity and density of the MWs were also measured in both studies. Across the range of concentrations investigated, sugar influences the perception of viscosity and density the most, ethanol has a moderate effect and the contribution of glycerol is nominal. In model ice wine solutions, PV and PD increased with sugar concentration, but were minimally affected by changes in ethanol concentration. The PV elicited by the model ice wine solutions was well described by a linear model using physical viscosity as the independent variable (r: 0.907). This information may be useful for predicting the sensory properties of the ice wine for quality control purposes.     

OPTIMUM LIMIT STATE DESIGN OF HIGHWAY BRIDGE SUPERSTRUCTURES USING GEOMETRIC PROGRAMMING

A number of studies, by the author and others, have shown that the Limit State Design method can, when applied to the design of bridge superstructures, produce more rational and economic designs than conventional methods. Most studies have been made on the assumption that the basic structural layout, proportioning, and material characteristics would be determined by the rules used for conventional design. The authors have pointed out that these rules are possibly no longer applicable and that greater economies could be obtained by some form of optimization procedure.

This paper describes the application of Geometric Programming to the solution of such a problem. It is shown that excellent results can be obtained with a simplified version of the technique in which the “degree of difficulty” is reduced to zero. The superiority of Geometric Programming as an optimum design technique is demonstrated by comparing the results for the example chosen with those obtained by alternative methods.     

The cost of eliminating exceptional elements in group technology cell formation

Many researchers have suggested methods for the formation of machine cells/part families in group technology. However, few of these methods have addressed the possible existence of exceptional elements (EE) in a reasonable manner. EE can be the result of bottleneck machines whose processing is needed by parts assigned to more than one part family. They can also be caused by parts that require processing on machines assigned to more than one machine cell. The existence of EE in cell formation solutions is a nontrivial problem that requires interaction between machine cells intended to be independent for production efficiency. This paper presents a systematic method for identifying opportunities for reducing the number of intercell transfers caused by the existence of EE. The method recognizes how each EE in a cell formation solution may be involved in the creation of intercell transfers. The sequence of operation in each part routeing is also considered. The method then analyses the costs associated with alternative actions for the removal of the EE. The result is a prioritized list (based on relative cost-effectiveness) of the EE-removal actions. The method recognizes that interdependencies exist among EE: actions taken to eliminate one EE may have an effect on others as well. The process is demonstrated with an example.     

The efficiency and economics of small heterogeneous labour limited queueing systems

This paper presents an evaluation of heterogeneous labour patterns in small, labour limited queueing systems. Three heterogeneous labour patterns, a homogeneous labour force and two labour assignment rules are examined. The experimental systems consist of three machine centres in parallel, each with its own queue. The arrival process is Poisson, and the queue priority rule is first-come-first-served. Each machine centre contains one machine, and the service times are exponentially distributed. The number of labourers is two. The experimental model is a GERTS QR stochastic network simulator. The evaluation focuses upon the relative merits of the various labourer efficiency patterns and offers an economic interpretation of the experimental results.