Job Ubbink

University of Minnesota

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W.J.H. Vermaak

University of Pretoria

Rhena Delport

University of Pretoria

Piet Becker

University of Pretoria

W J Serfontein

University of Pretoria

S. Bissbort

University of Pretoria

Ana Silvia Prata

Universidade Estadual de Campinas (UNICAMP)

L S de Villiers

Tygerberg Hospital

Mina Roussenova

University of Bristol

Belal J. Muhialdin

Universiti Putra Malaysia

Prisca Schär-Zammaretti

Nestlé (United Kingdom)

Cooperative Institutions

University of Pretoria

University of Bristol

Nestlé (Switzerland)

University College London

University of Oxford

Medical Research Council

Radboud University Nijmegen

North-West University

Universidade Estadual de Campinas (UNICAMP)

Wageningen University & Research

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Optimization of the rotor surface resistance of the asynchronous electrostatic motor

Applied Scientific Research (1970)

Job Ubbink

10.1007/bf00400547

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Citations (16)

Food structure and functionality: a soft matter perspective

Soft Matter (2008)

Job Ubbink Adam Burbidge Raffaele Mezzenga

The structure and functionality of foods are described from the perspective of recent advances in soft condensed matter physics. An overview is given of the structure and properties of food materials in terms of the physically relevant length scales. Recent developments in the understanding of the physics of gels, micelles, liquid crystals, biopolymer complexes and amorphous carbohydrates are presented.

Soft matter

Biopolymer

Soft materials

10.1039/b802183j

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Citations (191)

Analytical recovery of protein-bound pyridoxal-5′-phosphate in plasma analysis

Journal of Chromatography B Biomedical Sciences and Applications (1986)

Job Ubbink W J Serfontein L S de Villiers

Pyridoxamine

Coulometry

10.1016/s0378-4347(00)83734-2

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Citations (24)

High-performance liquid chromatographic assay of human lymphocyte kynureninase activity levels

Journal of Chromatography B Biomedical Sciences and Applications (1991)

Job Ubbink W.J.H. Vermaak S. Bissbort

10.1016/0378-4347(91)80253-9

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Citations (19)

Flavor Delivery Systems

Kirk-Othmer Encyclopedia of Chemical Technology (2013)

Job Ubbink

Abstract An overview is given of flavor delivery systems and technologies for flavor encapsulation. A distinction made is between ( 1 ) systems aimed at protecting the encapsulated flavor against evaporation and the adverse effects of environmental oxygen in low‐moisture states, and ( 2 ) those whose principal aim is to modify the release of the encapsulated flavor during food processing, storage, or consumption. The former class of systems, designated as glass‐encapsulation systems because they are invariably based on amorphous carbohydrates in the glassy state, is generally prepared by well‐established technologies like spray drying and melt extrusion and has found widespread commercial application. Accounts are given of the most‐used technologies and of the underlying materials science. The latter class of systems, principally aimed at controlling the release rate of the encapsulated flavor, is far more diverse in composition, working principle, and manufacturing technology. Several principal technologies are highlighted, and examples are given of successful applications in food matrices.

Encapsulation

10.1002/0471238961.0612012221020209.a01.pub2

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Citations (8)

Theophylline increases pyridoxal kinase activity independently from vitamin B6 nutritional status.

PubMed (1993)

Rhena Delport Job Ubbink W.J.H. Vermaak Piet Becker

Asthmatics treated with theophylline, a potent inhibitor of pyridoxal kinase and therefore a vitamin B6 antagonist, demonstrated a significant correlation (r = 0.71; p < 0.001) between drug plasma levels and erythrocyte pyridoxal kinase activities. A cross-over, placebo controlled study was completed on 15 healthy volunteers to investigate the mechanism by which theophylline induces pyridoxal kinase activity. The subjects were supplemented with vitamin B6 or placebo for two weeks before theophylline therapy was started. Vitamin B6 supplementation resulted in a four-fold increase in circulating pyridoxal 5'-phosphate levels, while placebo had no effect. When theophylline therapy was commenced, erythrocyte pyridoxal kinase activities increased significantly (p < 0.001) irrespective of whether vitamin B6 or placebo was supplemented. It is concluded that a depressed vitamin B6 status is not responsible for higher erythrocyte pyridoxal kinase activities encountered during theophylline therapy, but that the drug is directly responsible for elevated enzyme levels.

Pyridoxal phosphate

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Citations (9)

Delta-6-desaturase enzyme co-factors and atherosclerosis.

PubMed (1985)

W J Serfontein L S de Villiers Job Ubbink C.H. Rapley

Source

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Citations (2)

Materials Science Approaches towards Food Design

Job Ubbink

This chapter contains sections titled: Introduction Consumer-driven food design Food design based on the supplemented state diagram Design of foods and encapsulation systems in the glassy state Retro-design for the delivery of bioactive ingredients in foods Concluding remarks References

Food Products

10.1002/9781118373903.ch7

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Citations (3)

Effect of water content and aging on the elastic properties of extruded pea protein isolate

Physics of Fluids (2023)

Job Ubbink Belal J. Muhialdin

The effects of water on the elastic properties of extruded pea protein isolate (PPI) are investigated transversally to the fiber direction in the water content range between 40% w/w to 60% w/w. Young's modulus of elasticity in the transversal direction was found to decrease linearly with the water content from 2.6 MPa at a water content of 40% w/w to 0.6 MPa at the water content of 60% w/w at T = 21 ± 1 °C. Matrices extruded at different water contents of which the water content was adjusted to 60 ± 1% w/w showed decreasing values of Young's modulus. This variation in the transversal Young's modulus correlates linearly with the specific mechanical energy, confirming the impact of processing on the development of the protein network. The kinetics of aging of the extruded PPI matrices at T = 4 °C were fitted using an exponential equation and were observed to be dependent on the water content. Characteristic aging rates varied from an aging rate of ∼0.1 h−1 for the matrices extruded at a water content of 40% w/w to ∼0.015 h−1 for the matrices extruded at a water content of 60% w/w. The degree of aging was found to be 43.2 ± 7.5%, independent of the protein content of the matrices. The current study is the first systematic investigation of the elastic properties of extruded plant protein matrices in the concentration range that is relevant for meat analogs and may serve in process optimization and product development as well as for fundamental studies into the properties of concentrated protein networks.

Content (measure theory)

Water activity

10.1063/5.0161352

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Citations (4)

Solubility and Diffusion of Nitrogen in Maltodextrin/Protein Tablets

Biotechnology Progress (2002)

Annemarie Schoonman Job Ubbink Chris Bisperink Martine Le Meste Marcus Karel

The gas transport properties of compacted tablets consisting of an amorphous mixture of maltodextrin and sodium caseinate were studied by dissolving nitrogen gas in the tablets and then determining the gas release over time as a function of temperature and water activity. Gas was dissolved in the tablet matrix by heating the tablets under pressure, generally to temperatures above the glass transition temperature of the matrix, holding them at these conditions for a specified time and then rapidly cooling them while maintaining the external pressure. The solubility of nitrogen was found to be largely determined by the free volume of the matrix, which in turn can be influenced to some degree by thermal and pressure treatments during gas loading. At the levels of free volume studied, the dissolved nitrogen is densely packed in the free volume, the packing density being virtually independent of the externally applied pressure. Release of gas from the tablets at temperatures below the glass transition temperature is generally well described by Fickian diffusion. The effective diffusion coefficient of gas release is strongly dependent on the microstructure and porosity of the tablet matrix, and an approximate model describing the relationship between tablet structure and rate of gas release is formulated. The model is in semiquantitative agreement with the rates of gas diffusion obtained for tablets and dense granules. Owing to the structural heterogeneity and variability of the tablets and the history-dependent properties of the tablet matrix, the effective diffusion coefficients of gas release from the tablets showed a relatively large spread. The temperature dependence of diffusional release follows an Arrhenius relation below the glass transition temperature. This allows the prediction of the nitrogen retention in the tablets as function of time, temperature and pressure.

Maltodextrin

Matrix (chemical analysis)

Gaseous diffusion

10.1021/bp010126f

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Citations (34)