PINEAPPLE JUICE CONCENTRATED BY OSMOTIC EVAPORATION1

Pasteurized pineapple juice was concentrated by osmotic evaporation to produce a 51 d?Brix concentrate that was reconstituted to single strength juice for evaluation. Headspace gas chromatography (HSGC) showed that the concentrate retained an average of 62% of the volatile components present in the initial juice. A sensory panel preferred initial juice over reconstituted concentrate, and noted a decrease in desirable flavor top notes as well as development of some processed flavor in the concentrate. Similar HSGC analysis of four other commercial juice samples showed a wide range of quantitative values for volatile components, with the initial juice being similar to the weakest of these commercial juices. Analysis of concentrated juice extracts permitted identification of additional less‐volatile components not monitored directly by HSGC of the juice. Relatively low levels of these components were also present in the initial juice. Although this nonthermally produced concentrate retains more volatile components than when traditional thermal processing methods are used, addition of aqueous aroma to the concentrate may be required for satisfactory flavor.     

SCREEN PRINTED AND SINTERED CdTe-CdS SOLAR CELLS

Screen printed and sintered CdTe-CdS solar cells differ in some aspects from other CdTe cells: the layers are thicker, the fabrication temperatures higher, the grain size is usually better. A good morphology, a good junction behaviour and consequently a high open circuit voltage, and efficient doping of the CdTe are seen to be an inherent advantage of the screen printing and sintering technology. On the other hand, care has to be taken to avoid strong interdiffusion and optical transmission loss in the CdS window.     

ANALYSIS OF MASS TRANSFER IN OSMOTIC DEHYDRATION BASED ON PROFILES OF CONCENTRATION, SHRINKAGE, TRANSMEMBRANE FLUX AND BULK FLOW VELOCITY IN THE DOMAIN OF TIME AND SPACE

An analysis of mass transfer mechanisms in osmotic dehydration was carried out by examining the profiles of concentration, shrinkage, transmembrane flux and bulk flow velocity in the domain of time and space. The profiles were obtained through simulations using a computer simulation model that described mass transfer in osmotic dehydration based on cellular structure. It was shown that bulk flow was the main resistance for solute penetration, and the magnitude of bulk flow was affected not only by the transmembrane flux, but by internal cellular structure changes. Since bulk flow often played an important role in mass transfer during osmotic dehydration, precautions should be taken when interpreting mass transfer in osmotic dehydration using a simple pure diffusion theory.     

IDENTIFICATION OF VOLATILE DATE COMPONENTS AND USE OF MULTIVARIATE ANALYSIS TO DISTINGUISH DATE VARIETIES1

Pentane extracts which possessed strong date-like aromas were obtained from three date varieties and analyzed by gas chromatography-mass spectrometry. Thirty-six volatile components were identified and only six of these had been found earlier in dates. Many of these components possessed aromas and flavors which could contribute to the sensory characteristics of dates, suggesting that a combination of volatile components is responsible for the desirable flavor of dates. Headspace gas chromatographic analysis of fresh dates from each of the three varieties combined with multivariate analysis involving eleven of the known constituents was used to distinguish differences among the varieties.     

KINETICS OF LYCOPENE DEGRADATION IN TOMATO PUREE BY HEAT AND LIGHT IRRADIATION

Lycopene as a natural antioxidant may provide protection against a broad range of epithelial cancers. Tomatoes and tomato‐based food products are a major source of lycopene compounds. Thermal processing is the main procedure in tomato puree production. Heat and light induces lycopene oxidation and isomerization of the all‐trans form to the cis form. The level of cis‐isomers increases as treatment time increases but only for a short period during the beginning of the treatment. The major effect of thermal processing was a significant decrease in the total lycopene content. Lycopene is relatively stable if heated at temperatures below 100C, but the duration of heating must be taken into consideration. The kinetics of lycopene degradation was analyzed. A shorter period of time of heating and less light irradiation in processing and storage would reduce lycopene degradation to a great extent.     

SEMANTIC ANALYSIS AND IN-DEPTH UNDERSTANDING OF TECHNICAL TEXTS

We explored the problem of achieving in-depth understanding of natural language sentences from narrative technical reports through knowledge-based free text understanding. We rely on the assumption that texts in an expert domain convey much implicit information, which can be recovered by building and reasoning on a model of the situation described with the help of both linguistic and detailed world knowledge. We describe a two-step approach to semantic analysis: the first step assembles a conceptual representation of a sentence and deals with linguistic issues; the second step actually builds and runs the situational model and is totally dedicated to representation and inference. We evaluated this approach by designing a research prototype that processes sentences from clinical narratives in a medical specialty. This prototype was fully implemented and was tested on actual sentences. We hereby give a detailed account of this implementation as well as the first results obtained.     

QSVD approach to on- and off-line state-space identification

Moonen et al. (1989 a), presented an SVD-based identification scheme for computing state-space models for multivariable linear time-invariant systems. In the present paper, this identification procedure is reformulated making use of the quotient singular value decomposition (QSVD). Here the input-output error co-variance matrix can be taken into account explicitly, thus extending the applicability of the identification scheme to the case were the input and output data are corrupted by coloured noise. It turns out that in practice, due to the use of various pre-filtering techniques (anti-aliasing, etc.), this latter case is most often encountered. The extended identification scheme explicitly compensates for the filter characteristics and the consistency of the identification results follows from the consistency results for the QSVD. The usefulness of this generalization is demonstrated. The development is largely inspired by recent progress in total least-squares solution techniques (Van Huffel 1989) for the identification of static linear relations. The present identification scheme can therefore be viewed as the analogous counterpart for identifying dynamic linear relations.