The aggregation behavior of starch granules during cooking was investigated. Granular aggregation was found to depend mainly on water content and degree of conversion (cooking) of starch. There were threshold values of water content and degree of conversion for powdery starch to undergo a phase transition from a nonaggregated to an aggregated state. A method for determining such threshold values of the transition was developed. A mathematical model was also developed to describe the aggregation behavior of cooked starch. Its potential application to food systems, especially to the simulation of starch extrusion process, was discussed.
Typical DSC thermograms of starch phase transition in the low moisture content range (15‐40%) showed two thermal transition peaks. This suggests the existence of two different cooking mechanisms. We call them gelatinization and melting. “Gelatinization” describes thermal transition of starch with water and “melting” without water. Kinetics of the formation of gelatinized starch (GEL) and melted starch (MELT) were studied. Conversions caused by gelatinization and melting were separately analyzed by using information from DSC (Differential Scanning Calorimetry) isothermal studies. The rate of formation of gelatinized fraction followed first order kinetics and that of melted fraction zeroth order. The overall reaction rate followed zeroth order because melting is the dominant mechanism of the two under limited water contents of extrusion cooking conditions.
Abstract:The aim of this study was to assess the efficacy of an oral supplement (CP) containing collagen peptide, soy peptide, and chrysanthemum extract in Chinese female adult volunteers with melasma. The approval of the Institutional Ethics Committee of the third affiliated hospital, Sun-Yat Sen University, was obtained before the study. A signed consent was obtained from each volunteer prior to study to enable the volunteer to appreciate the aim of the study and the consequences of her consent. Sixty-two female volunteers aged 30-60 years were included in the study, and were randomized into a treatment group or a placebo group. The skin tone of the pigmented spots was evaluated using Chromameter, and pigment density was evaluated using Mexameter before and after the treatment. Significant changes in skin tone parameters of L value and ITA • (individual typology angle) were detected in the lesion area after the treatment (P < 0.01). When compared with placebo group, the treatment group achieved significant improvement in the brightness of the pigmented spots at the 45 and 60-day time points. A significant decrease in the level of melanin was observed in the treatment group when compared with the placebo group (p < 0.01). All data demonstrated through non-invasive in vivo instrumental measurement that daily oral intake of CP had clinical efficacy of reducing melasma severity.
Objectives Translucent skin is an attribute widely appreciated by people in East Asian countries. There have been studies in the literature to describe the phenomenon by means of clinical grading, instrumental measurement and image analysis. However, due to its subjective and complex nature, skin translucency has not been comprehensively and rigorously characterized and modelled, particularly in the Chinese population. This study is to develop a mathematical model that quantitatively describes skin translucency from visual cues objectively measured from the skin. Materials and Methods The study was designed to characterize and model skin translucency by incorporating expert evaluation, panel perception and image analysis of multiple skin visual attributes in one analysis. Faces of 36 Chinese females aged 18–65 years old were evaluated by a dermatologist to obtain clinical translucency scores. Subject pairs were formed with a relatively high and low translucency score in each pair. Their faces were judged in person by 9 panellists in paired‐comparison (2‐AFC) fashion to pick a ‘more translucent skin’ from each subject pair. Front‐view facial images of the subjects were taken, and multiple colour and other visually perceivable skin attributes were measured using image analysis. Bradley‐Terry analysis and multiple regressions were performed to correlate the panel choices of ‘more translucent skin’ with the objectively measured skin parameters. Results Multiple skin colour properties affected the panel choices towards translucent skin. Among them skin tone lightness and skin glossiness had positive effects on skin translucency while the hue, colour unevenness, severity of red and dark spots affected it negatively. Subsurface light reflection and skin visual smoothness had some effect but were not statistically significant. A mathematical model was constructed to predict a person's skin translucency from objectively measured skin attributes. Conclusion The subjective property of skin translucency can be characterized and quantified via a comprehensive modelling process involving clinical grading, panel evaluation, image‐based measurement of skin attributes and statistical analysis. A novel skin parameter, Skin Translucency Index (STI) was established, which provides a way to measure skin translucency, making it possible to assess treatment efficacy before and after product application.
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