No abstract

Three highly reproducible food models have been developed to evaluate rheological and functional properties of starches. The food models are dutch vla, dressing, and white sauce, and they vary in pH, serving temperature, oil content, and content of other functional ingredients than starch (milk proteins, whole egg, carrageenan). The viscous properties were calculated in a controlled stress rheometer, and the power law index, n, and the consistency index, K, was calculated. The viscoelastic properties at small deformations were measured by oscillating viscometry. Also a spreadability analysis was performed. The rheological data for the three food models were analysed by use of a principal component analysis (PCA), which enabled an evaluation of the functionality of the models and visualisation of the correlation to the concentration of starch. The rheological parameters all varied significantly with starch concentration in dutch vla. In dressing and white sauce most of the rheological parameters depended on the starch concentration. In addition, it was found that results from the empirical rheological method (USDA consistometer) correlate well with fundamental rheological parameters. Syneresis was measured for a period of time up to 15 days. The degree of syneresis of dressing was highly dependent on starch concentration, while the syneresis of the white sauce was dependent on time but not on starch concentration. The dutch vla showed no syneresis at all.

Objective: To study processing and fermentability in the human gastro-intestinal tract of a newly isolated, enzymatically modi®ed, soluble, and highly concentrated ( b 80% dietary ®bres) solubilised potato ®bre (SPP). Setting: Gastroenterological laboratory. Design, subjects and interventions: Seven healthy volunteers ingested in random order on seven different days: 20 g SPP; bread made of 180 g wheat¯our served with 20 g raw SPP; bread baked of 180 g wheat¯our and 20 g SPP; bread made from 180 g wheat¯our; 20 g lactulose; 20 g oat bran; and 20 g wheat bran. The hydrogen breath test was used to evaluate oro-coecal transit time (OCTT) and fermentation. Results: Fermentation of SPP yielded a measurable increase in end-expiratory H 2 . The total incremental increase in end expiratory H 2 due to SPP was unaffected of whether SPP was served alone, as the raw¯our served with bread, or baked into bread. The OCTT for raw SPP was signi®cantly delayed compared to lactulose (P 0.01). The OCTT for SPP baked into bread was signi®cantly delayed compared to raw SPP (P 0.01), indicating that SPP may be used as a marker of oro-coecal transit time for as well the¯uid phase as the solid phase of a meal. Conclusions: SPP is a fermentable, highly concentrated soluble ®bre source. Baking SPP did not interfere with the fermentable properties. Thus, SPP may be interesting as a ®bre-supplement in ®bre-poor diets. The change in oro-coecal transit time for SPP, depending on the composition of the total meal, makes SPP interesting as a marker in studies of gastrointestinal transit.

Insoluble potato dietary fibre, isolated from potato pulp, can be enzymatically hydrolysed with the pectolytic enzyme preparation Pectinex Ultra SP from Novo Nordisk A/S, in order to produce soluble fibre. The soluble fibre has valuable functional properties for the food industry. Cloned monocomponent enzymes from Pectinex Ultra SP (arabinofuranosidase, endoglucanase II, pectin lyase, polygalacturonase I, rhamnogalacturonan acetyl esterase, rhamnogalacturonase a, rhamnogalacturonase b and xylanase I) were added in order to increase the yield. Surprisingly, however, the yield is not increased when any of the monocomponent enzymes are added. To describe the results a new model designated 'the competitive activity adsorption model' is proposed. The model is based on the fact that the enzymes are adsorbed to the substrate before action. A combination of the Langmuir adsorption isotherm and basic enzyme kinetics shows that different enzymes that adsorb competitively will have an inhibitory effect on each other and consequently decrease the hydrolysis rate and thereby the yield. The model has been confirmed by an experiment in which the fibre has been pre-treated with rhamnogalacturonan acetyl esterase.

Correspondence analysis partial least squares (CA-PLS) has been compared with PLS conceming classification and prediction of unimodal growth temperature data and an example using infrared (IR) spectroscopy for predicting amounts of chemicals in mixtures. CA-PLS was very effective for ordinating the unimodal temperature data and the results indicated that CA-PLS is effective in treating the arch effect, thus avoiding the detrending procedure often used on ecological data sets, at least when one basic underlying gradient is present. PLS and PCR gave poor results, as the ordinations had a horseshoe form that could only be seen in two-dimensional plots, and also less effective predictions. PLS was the best method in the linear case treated, with fewer components and a better prediction than CA-PLS. O 1996 by John Wiley & Sons, Ltd.