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The effect of thiolation using propanethiol on the functionalities of fibrillated whey protein isolate (WPI) solution at different pH values was studied. Fibrillated WPI solutions were thiolated at different molar ratios of propanethiol:carboxyl group (0.5:1, 1:1, 2:1, 3:1, 4:1) and the highest esterification extent ratio was obtained at 4:1 (pH 9). We also found that the thiolation process improved the foaming capacity and foam stability. TEM micrographs evidenced aggregation of thiol-modified fibrillated WPI. A network of shortened fibrils attached to each other was formed upon thiolation, suggesting good physical interaction. This was coherent with the increment of zeta potential values, indicating a greater repulsion force to retard fibrils aggregation. Thiolation enhanced emulsifying stability index of thiol-modified fibrillated WPI solution (pH 8) and diminished its susceptibility to pH changes. This has broadened the potential application of fibrils as food ingredients.

The present research investigated the effect of microfluidization treatment (103, 138, 172, and 207 MPa) on pH, refractive index (RI), color measurements, rheology, particle size, emulsifying properties, and thermal denaturation of egg yolk. Color parameters were significantly (p τ o ), consistency constant (K), and flow behaviour index (n) were affected by microfluidization. Microfluidization caused a reduction in particle size of yolk with an increase in pressure up to 172 MPa and particle size increased at 207 MPa. Emulsifying activity index (EAI) increased from 30.49 m2/g (control) to 32.41 m2/g (MEY2) but decreased as microfluidization pressure was increased. Emulsifying stability index (ESI) increased at 103 MPa but decreased as microfluidization pressure increased further. Thermal analysis revealed increase in denaturation temperature as microfluidization pressure increased.

A freshness index called the global stablity index (GSI) applicable to follow the variation of multi-quality indices of bighead carp (Aristichthys nobilis) heads during different temperatures storage was evaluated. Quality indices (sensory score, total aerobic counts, volatile base nitrogen, and K value) were estimated and calculated into the single parameter GSI at −3, 0, 3, 9 and 15 °C. GSI was then kinetically modeled to describe the dependency of GSI with temperature and storage time. The calculated data of GSI were satisfactorily described by a zero order kinetic model. The activation energy (EA) and the corresponding pre-exponential constant (k0) of GSI were 85.61 kJ/mol and 1.14 × 1015, respectively. Relative errors between predicted and observed GSI values were all below 10% before the 15th day. Thus, the established model based on GSI could effectively predict the freshness of bighead carp heads at the range of −3 and 15 °C during different temperatures storage.

Gums and proteins are valuable ingredients with a wide spectrum of applications. Surface properties (surface tension, interfacial tension, emulsion activity index “EAI”, and emulsion stability index “ESI”) of 4% whey protein concentrate (WPC) in a combination with ι-carrageenan (0.05%, 0.1%, and 0.5%) or gum arabic (0.5%, 1%, and 5%) were investigated. The results showed that the addition of ι-carrageenan to 4% WPC significantly decreased interfacial tension, and improved the EAI, and ESI, but addition of gum arabic to 4% WPC significantly increased the interfacial tension, EAI, and ESI. In addition, a fuzzy-based clustering model was used to predict the surface properties. The fuzzy model achieved accuracies of (94%, 97%, 98%, and 94%) for predicting (EAI, ESI, surface tension, and interfacial tension), respectively.

This study consists of introducing a new method that may be used to globally quantify the quality degradation of a food product during storage or commercialization. The new concept is based on defining and formulating a single index called the Global Stability Index (GSI), varying between zero and one and taking simultaneously into account the time variations of all pertinent quality indices proper to the food product under study. This index enables one to judge the degradation of the microbiological, the physicochemical and the sensory quality of the food product during storage in a global fashion. The new method, referred to as the GSI method, has been successfully tested in studying the stability of an orange based carbonated beverage by simultaneously considering the time variations of the brix and the CO2 partial pressure of the drink. It is particularly recommended that the proposed index is to be used in comparing the quality degradation rates of a given food product stored under different conditions or those of different products stored under a common set of conditions.

in this work, a methodology to evaluate foaming capacity and stability is proposed. With this method the foam volume decay is followed and the overrun [(foam volume -solution volume)isolution volume] plotted against time. The integral of overrun decay for a jixed period was tried out as a single parameter to describe foam properties, i.e. foaming capacity and foam stability. It was concluded that using this single parameter; the foaming stability index (ES.I.),, the application of statistical experimental design methodology to optimise foaming becomes straightforward. As an example of an application of this method, the denaturation extent of the protein was optimised to improve the foaming properties of Lupin protein isolate. 0 1998 Elsevier Science Limited. A 11 rights reserved