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X-ray micro-computed tomography (micro-CT) is a non-destructive method to study internal structures based on the differences in the strength of x-ray attenuation within a scanned material. In the field of food science, distinguishing certain components represents a challenge as food ingredients have low x-ray attenuation. The objective of this study was to explore the potential application of different agents to enhance x-ray attenuation in fried starch-gluten products, quantify oil content and air porosity, and analyze its microstructure using micro-CT. Control dough, dough stained with a Lugol solution (0.1% (w/w)) or with a BaCl 2 solution (0.5% (w/w)), and samples fried in oil stained with Nile Red (0.05 g/L) or stained with Lugol solution and fried in Nile Red were examined. All agents studied improved x-ray attenuation in fried dough. Quantitative analysis of micro-CT images showed that samples attenuated with Nile Red exhibited the smaller standard deviation in oil content and air porosity. These results did not show significant differences with those determined by means of traditional analytical methods. [ABSTRACT FROM AUTHOR]

Highlights: [•] Microstructure of fried gluten or potato-flakes based products was characterized. [•] A non-invasive double staining procedure allowed confocal microscopy observation. [•] Oil and pore structure were characterized qualitatively and quantitatively. [•] A direct relationship of porosity and oil uptake was found in gluten-based products. [•] Gluten-based products were less porous but retained, in general, more oil. [Copyright &y& Elsevier]

In vitro studies have shown that vacuum frying may be an effective process to reduce starch digestibility as it may limit gelatinization; this is significant as overconsumption of starchy foods contributes to obesity and type 2 diabetes. Although in vitro studies are an instrumental tool, in vivo studies allow observation of the overall effect on a living organism. The aim of this research was to assess how in vivo starch digestibility can be reduced when frying under vacuum (9.9 kPa), after feeding Sprague-Dawley rats, while also understanding its relationship to in vitro starch digestibility. Results showed that vacuum-fried dough has a lower degree of gelatinization (∼53.8%) and a maximal blood glucose level at 60 min (slower glycemic response) than atmospheric counterparts (∼98.3% degree of gelatinization and maximal blood glucose level at 30 min). Similarly, in vitro procedures exhibited less rapidly available glucose and higher unavailable glucose fractions in vacuum-fried dough. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this work is to examine the relationship between surface roughness and oil uptake in fried fabricated products. Two product categories were studied, using formulations based either on potato flakes or wheat gluten. Products were deep-fat fried at 170°C and two oil fractions, penetrated oil and surface oil, were determined at the beginning and at the end of cooling period. The surface of fried products was measured using a scanning laser microscope and characterized by an area-scale fractal analysis. Within each product category, products with higher surface roughness retained more oil. However, this relationship could not be extended when comparing products of different categories. Potato-flake-based products were rougher than gluten-based products, but retained less oil. Further, gluten-based products absorbed most of the oil during frying, whereas potato-flake-based mostly absorbed oil during cooling. Certainly, surface roughness is a key factor in oil absorption, but other food-related properties, such as the micro-structure of the crust, may explain differences among product categories and should be examined in future studies. [ABSTRACT FROM AUTHOR]

Abstract: Bloom development and associated fat migration were analyzed from a microstructural viewpoint. To do so, chocolate model bars were prepared by tempering a mixture made of sand particles (mean sizes of 120, 55 and 5μm) and cocoa butter (68% and 32% by mass, respectively). Model bars initial microstructure was characterized by means of confocal and electron microscopy, along with image analysis. Bloom was induced by storing model bars at 30°C and was assessed by measuring the amount of migrated fat to the surface and the change in surface colour (whiteness index). Both measurements showed an initial rapid increase followed by a gradually decreasing gradient until reaching an asymptotic value. Importantly, it was determined that density change is a key factor in bloom development. Also, a higher fat migration rate was determined in small particle size bars. [Copyright &y& Elsevier]

Starch digestibility in a food matrix depends on processing conditions that may affect its physical state and microstructure. Starch gelatinization is one critical change that takes place during frying which could be affected during low-pressure processing. This study assessed the effect of vacuum frying on starch gelatinization and its in vitro digestibility. Laminated dough was made of a reconstituted blend of wheat starch (88% d.b.) and gluten (12% d.b.). Samples were fried under vacuum (6.5 kPa, T water-boiling-point = 38 °C) or atmospheric conditions up to bubble-end point, maintaining a thermal driving force of 70 °C ( T oil − T water-boiling-point = 70 °C). Vacuum fried samples showed less starch gelatinization (28%), less rapidly available glucose (27%), and more unavailable glucose (70%) than their atmospheric counterparts (which presented 99% starch gelatinization, 40% rapidly available glucose , and 46% unavailable glucose ), and the values were close to those of raw dough. These results show how vacuum processing may be used to control the degree of starch gelatinization and related digestibility. [ABSTRACT FROM AUTHOR]

Highlights: [•] It was possible to mimic the frying process using glass micromodels. [•] We got evidence of the sequence of transport phenomena during oil immersion. [•] A small fraction of oil was able to penetrate during the immersion period. [•] Once the release of steam stopped, after some cooling, oil-uptake began abruptly. [•] Oil absorption stopped as soon as the oil film lost its continuity. [Copyright &y& Elsevier]