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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 BaCl2 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.

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.

Objectives: To study the effect of deep fat frying on the mass transfer and color changes of ArepaCon Huevo. Methods: The product was prepared as a round plate (diameter: 10 cm and thickness: 2.5 cm). Palm oil was used in a 7 L fryer at 170, 180 °C and 190°C under a ratio of 250 g sample/L oil. Findings: Moisture content decreased as time and temperature increased (p

Olive leaves extract (OLE) was microencapsulated with inulin (OLE-IN) by spray-drying using a central composite design. Oleuropein encapsulation efficiency and recovery values were over 87% in the OLE-IN microparticles obtained under optimal conditions. OLE or OLE microparticles were added into starch–gluten fried matrices with the aim of studying the effect of microencapsulation and the frying method on the polyphenols content and antioxidant activity, fat content and crispness. Vacuum starch–gluten fried samples absorbed slightly, but significantly, less oil than the atmospheric fried ones (except for the dough with 350 mg GAE/kg), but crispness was higher in the atmospheric fried products. Although vacuum fried matrices showed significantly higher content of polyphenols than atmospheric fried matrices, both types of matrices showed similar antioxidant activity, suggesting the formation of antioxidant metabolites derived from the Maillard reaction during the atmospheric frying. The results highlighted the importance of the microencapsulation of OLE to preserve the beneficial effects of polyphenols in processed food.

Consumers like fried snacks, and taste, color, and texture are key aspects in their preference. However, during frying of foods some toxic compounds, such as furan and acrylamide, are produced. The objective of this work was to mitigate furan and acrylamide formation in potato chips, without affecting their main quality attributes, by using vacuum frying. To accomplish this purpose, potato slices were fried at atmospheric (P abs 29.92 inHg) and vacuum conditions (P abs 3.00 inHg), using equivalent thermal driving forces (T water boiling point − T oil = 50, 60, or 70 °C). Furan and acrylamide concentration, oil content, and texture of both atmospheric and vacuum-fried samples were determined. Vacuum-fried potato chips showed reductions of about 81, 58, and 28% of furan, acrylamide, and oil content, respectively, when compared to their atmospheric counterparts. Additionally, the texture was not affected (p > 0.05) by changes in the pressure during frying. Results clearly showed that vacuum frying is an effective technology for furan and acrylamide mitigation in potato chips, since it reduces the content of both contaminants and preserves the quality attributes of fried snacks.

Sucrose not only provides sweetness, but also modifies the thermal/viscoelastic behavior of dough during baking. Most research on biscuit manufacturing has been focused on sugar-snap and wire-cut biscuits, and there is a lack of accumulated knowledge with respect to rotary-moulded biscuits. The aim of this study was to analyze the effect of the sucrose:flour ratio and the particle size of sucrose on dough expansion and starch gelatinization during the baking of rotary-moulded biscuits, together with their link to sweetness perception. X-ray micro-CT and scanning electron microscopy were used to ascertain the link between sensory attributes and biscuit structural properties. Image analysis showed that biscuits with lower levels of sucrose resulted in a microstructure with smaller air pores and thinner walls, which may be related to a lower degree of grittiness and hardness at the first bite. Furthermore, the results revealed the partial gelatinization of starch in all formulations, along with a gelatinization degree that increased from 6 % to 40 % as the sucrose content decreased from 40 % to 10 % (d.b.). Interestingly, biscuits that were formulated with powdered sucrose at the highest concentration attained an expanded and non-collapsible structure, a behavior that could be linked to the low degree of starch gelatinization.

Polyphenols are very unstable and may be degraded when exposed to harsh conditions, such as those found in frying. The inclusion of vacuum seems to be a reasonable solution to avoid these adverse effects. Accordingly, the purpose of this study was to analyze the effect of olive-leaf polyphenol extract on quality parameters of vacuum and atmospheric fried gluten-starch matrices. Matrices were prepared using 12% (d.b.) gluten and 88% (d.b.) starch, using either native or a mixture of native (90%) and pre-gelatinized starch (10%). Polyphenols were added as a freeze-dried powder. Atmospheric and vacuum (91.4kPa, Twater boiling point=46°C) frying were compared using an equivalent thermal driving force, which is defined as the difference between oil temperature and water boiling point at the working pressure. Bioavailability of polyphenols was evaluated using simulated digestion and caco-2 cells absorption. The addition of pre-gelatinized starch significantly decreased oil absorption in vacuum fried matrices, however, no significant differences were noted when added into atmospheric fried ones. Polyphenols retention was higher than 70% in vacuum fried matrices. Their bioavailability was ~15%, much higher than in atmospheric fried ones (~8%), and that the one reported in other studies. Interestingly, polyphenol addition reduced the oil content of vacuum fried snacks by 20%. This could be attributed to the hydrating effect of polyphenols, which may facilitate starch gelatinization, improving structure formation during vacuum frying, which will be the focus of future research.

Despite its importance, little attention has been paid to the effect of freezing on starch gelatinization during subsequent heating. In an effort to address this problem, the effects of freezing and water accessibility in starch gelatinization during heating were analyzed in situ using hot-stage polarized-light video-microscopy. Native starch granules immersed in water, carrageenan gel or sucrose solution were heated at 15 °C/min or frozen for 48 h and heated at 15 °C/min. Energy changes were measured using differential scanning calorimetry. Surface morphology was examined using scanning electron microscopy and atomic force microscopy. The results showed that freezing delayed the gelatinization degree and that the addition of carrageenan delayed the gelatinization process. That process was further delayed when sucrose was added. The enthalpy of gelatinization decreased accordingly (ΔHstarch−water−sucrose > ΔHstarch−water−carrageenan > ΔHstarch−water). The temperature range over which the degree of gelatinization differed between frozen and unfrozen samples was diminished when accessibility to water was reduced.

During vacuum frying, starch gelatinization may be limited due to the water boiling point depression, which reduces starch digestibility. In addition, relevant structural changes are induced, which could affect the accessibility of amylolytic enzymes to the site of action. To differentiate the effect of structural changes in the food matrix over the effect of starch gelatinization on starch digestibility, we characterized the microstructure using x-ray micro-computed tomography (micro-CT), confocal laser scanning microscopy (CLSM) and environmental scanning electron microscopy (ESEM), and we also studied the starch in vitro digestibility in two different systems: vacuum (9.9 kPa, Twater-boiling-point = 45 °C) and traditional atmospherically-fried dough (170 °C) with a similar degree of starch gelatinization (60 %). Vacuum-fried matrices had a much higher oil content (∼51.3 % dry basis) than their atmospheric counterparts (∼20.3 % dry basis), as confirmed through micro-CT and CLSM. The quantitative analysis of micro-CT images showed that vacuum-fried samples had less air porosity (36.6 % air-filled pores) than atmospheric fried ones (49 % air-filled pores), whereas, no differences were found with respect to total porosity (p

High consumption of starch-based foods is associated with type 2 diabetes, which has developed into a worldwide epidemic. Further, type 2 diabetes is also closely linked with obesity, as obese individuals often develop exacerbated insulin resistance. As changing the dietary habits of consumers is difficult, efforts may be directed at increasing the content of resistant starch in foods. Precluding starch digestibility through food product formulation or processing may be a reasonable alternative to reduce starch digestibility, slowing-down associated glycemic response. In this chapter, we examine main steps of starch digestion in the body, using a mass transfer perspective, in order to get a better understanding about how food properties (food composition and structure) as well as food processing may influence starch digestion.

Pablo CortesDept. of Chemical and Bioprocess Engineering, Pontificia Universidad Catolica de Chile, Santiago 6904411, ChileGuillermo Badillo and Luis SeguraDept. of Food Engineering, Universidad del Bio-Bio, Avda. Andres Bello S/N, Chillan, ChilePedro BouchonDept. of Chemical and Bioprocess Engineering, Pontificia Universidad Catolica de Chile, Santiago 6904411, ChileASIS-UC Interdisciplinary Research Program on Tasty and Healthy Foods, Pontificia Universidad Catolica deChile, Santiago 6904411, ChileDOI 10.1002/aic.15088Published online in Wiley Online Library (wileyonlinelibrary.com)Microstructure plays a key role in oil absorption during frying. The aim of this work was to improve our understandingof the relationship between microstructure and oil absorption, through the use of glass micromodels to obtain evidenceof transport phenomena in three porous networks. Micromodels were saturated with water and partially immersed in oilat 1908C. Moisture and oil profiles were imaged to get water and oil saturation maps. Image and fractal analyses wereperformed to describe the morphology of the evaporation and oil fronts. Results showed that higher porosity facilitatedthe moisture removal and promoted greater oil absorption during cooling. The fractal dimension showed that micro-structures with a relatively high number of fine capillaries were less stable and propitiated fingering during the advanceof the evaporation front. In all matrices, the disruption of the surface oil film due to air penetration was a critical factorto stop oil imbibition.

Great efforts have been made to elucidate the mechanisms responsible for oil absorption during deep-fat frying. This understanding can be certainly improved through direct visual observation. Accordingly, the goal of this study was to analyze mass transfer phenomena that develop during oil immersion by using glass micromodels partially submerged in oil (190 °C), to visualize the mechanisms responsible for moisture loss and oil absorption within a matrix, as well as the effect of gravity, for the first time, using three different configurations (g = 0, g 0). Moisture and oil profiles were imaged during the frying process in order to obtain water and oil saturation maps. Drying and oil curves were constructed using image analysis, and fractal analysis was performed to describe the morphology of the evaporation and oil fronts. If g < 0 (open side of the micromodel at the bottom) drying times were shorter and gravity tended to destabilize the drying front, which had a mean fractal dimension of 1.818 ± 0.032 that was significantly higher (p < 0.05) than those obtained in other set-ups. Largely, evaporation fronts tended to take the form of temperature profiles as reflected by infrared thermal imaging. The morphology of the advancing oil fronts was similar in all configurations. However, g severely affected oil content. When g = 0, less oil was absorbed with a final oil saturation of 32%. In all configurations the air inlet was a key factor to stop oil suction. This occurred even though enough oil could still remain on the surface. Overall, these results may help scientists to describe the physical mechanisms that develop during oil immersion and help presenting an interesting approach that may be used in other fields.

Food products must fulfill new demands of very well-informed consumers, and preferentially, positively contribute to their health and wellness. Accordingly, the snack industry is facing new challenges. Common processing technologies, such as baking or frying, may induce significant changes in the foodstuff, like the degradation of nutrition beneficial compounds, the formation of toxic compounds and/or the intake of degraded oil. These changes are directly linked to the use of high temperatures as well as the presence of oxygen.

Different studies have emphasized the importance of cooling in oil absorption after frying, suggesting that the largest proportion of oil is sucked into the crust after the product is removed from the oil. Microscopy has been a powerful tool to support these determinations, but, direct observation of fluxes has not yet been possible. The aim of this research was to develop an experimental procedure based on the use of glass micromodels to get direct evidence of transport phenomena during oil immersion for the first time. To do so, micromodels were saturated with water and immersed in oil at 190 °C. Fluids displacements were monitored using video-microscopy as well as fluorescence microscopy. Results showed that only a small fraction of oil penetrated during the immersion period, due to the vigorous escape of bubbles. Once the release of steam stopped, after some initial cooling, oil-uptake began abruptly and oil movement into the pores could be clearly identified. Oil absorption ended as soon as the oil film lost continuity, due to air penetration. Overall, the developed technique illustrates how glass micromodels may be used to visualize and provide valuable information to understand key transport phenomena during processing.

Low-fat and high dietary-fiber diets are important elements in the prevention of chronic diseases. The objective of this work was to understand the effect of wheat bran inclusion in large amounts to a gluten–starch matrix, in structure formation and associated quality attributes, during deep-fat frying. Matrices were prepared mixing 12 g of gluten and 88 g of wheat starch per 100 g of dry solids, ensuring a moisture content of 40 g water/100 g dough. Starch was gradually replaced by wheat bran (up to 40 g/100 g dry solids), and lack of structure formation was overcome by partially replacing starch with pregelatinized corn starch. Samples were fried at 170 °C and oil absorption in high fiber products was reduced through post-frying centrifugation. Pregelatinized corn starch addition allowed obtaining an adequate structure in formulations with high wheat bran content, reducing oil absorption by 35% in formulations with up to 20 g wheat bran/100 g dry solids. It was possible to obtain a low-fat product (70% reduction) with high fiber content (40 g/100 g dry solids) after centrifugation, confirming the importance of oil absorption during post-frying cooling.

Summary The optimal physical, chemical and nutritional properties of natural lipids depend on the structure and composition of triacylglycerols. However, they are not always mutually compatible. Lipid modifi cation is a good way to give them specifi c functionalities, increase their oxidative stability, or improve their nutritional value. As such, chemical and enzymatic interesterifi cation may be used to modify them and produce structured lipids. In accordance, the aim of this study is to compare chemical and enzymatic interesterifi cation of binary blends of fully hydrogenated soybean oil and walnut oil, using sodium methoxide or Lipozyme TL IM, respectively, to produce a fat base with adequate nutritional and physical characteristics. Three diff erent mass ratios of fully hydrogenated soybean oil and walnut oil blends (20:80, 40:60 and 60:40) were interesterifi ed and evaluated. Total interesterifi cation was determined by the stabilization of the solid fat content. Chemical reaction of the 20:80 blend was completed in 10 min and of the 40:60 and 60:40 blends in 15 min. Enzymatically interesterifi ed blends were stabilized in 120 min at all of the mass ratios. Complete interesterifi cation signifi cantly reduced the solid fat content of the blends at any composition. Chemical and enzymatically interesterifi ed fully hydrogenated blend of soybean and walnut oil at mass ratio of 40:60 showed the plastic curve of an all-purpose-type shortening rich in polyunsaturated fatt y acids, with a high linolenic acid (C18:3n3) content and with zero trans-fatt y acids.

Vacuum frying has gained a significant strategic importance for future fried food manufacturing since, due to the low-temperature processing, significant benefits such as the improvement of fried product safety and quality can be obtained. So far, all studies have focused on agricultural products, such as potatoes, which are already structured by nature, but none of them has included fabricated products. This imposes a challenge since minimum conditions must be ensured to form structure during processing. The objective of this work was to understand the role of water boiling point (T bp) and processing temperature (T oil) in structure formation, oil absorption, and most important quality attributes of starch-based products during vacuum frying. Fabricated products were made of a reconstituted blend of gluten (12 % d.b.) and wheat starch (88 % d.b.) in order to accurately control ingredients proportion. Samples were fried varying the T bp from 38 to 71 °C while keeping a thermal driving force of 70 °C (i.e., T oil − T bp = 70 °C). Another set of samples was fried varying the thermal driving force from 37 to 70 °C while maintaining a T bp of 71 °C. Results showed that a higher T bp favored the capacity of the matrix to form structure due to starch gelatinization in the presence of water and temperature, reducing the oil content of the fried products. This was confirmed by scanning electron microphotographs. Results were consistent with textural measurements that showed a higher breaking force as the processing pressure increased (i.e., T bp), which was inversely related to oil absorption (R 2 = 0.92). In accordance, this study allows understanding the effect of vacuum level in structure development and oil absorption in vacuum-fried products when different food building blocks (gluten and wheat starch) are combined.

Excess consumption of fat, a main component in fried food, is a key dietary contributor to coronary heart disease and perhaps some types of cancer. Although consumers are interested in healthier snacks, they are not willing to sacrifice organoleptic properties. Vacuum frying might be an alternative for the production of nutritious, healthy, palatable, and novel snacks. The objective of this review is to discuss the effect of atmospheric deep-fat frying on the main microstructural components and quality parameters of fried food, to understand how quality can be improved by lowering the operating pressure and, therefore, the processing temperature.

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.

Recent consumer trends towards healthier and low fat products have had a significant impact on the snack industry. The objective of this study was to examine the most important quality parameters of vacuum and atmospheric fried carrot slices in order to identify the specific advantages of vacuum technology. Said parameters include oil uptake, colour changes, and trans a and b-carotene degradation. Equivalent thermal driving forces were used (DT =6 0C and 80 C) to compare the processes, maintaining a constant difference in temperature between the oil and the boiling point of water at the working pressure. The results showed that vacuum frying can reduce oil content by nearly 50% (d.b.) and preserve approximately 90% of trans a-carotene and 86% of trans b-carotene. This process also allowed for the raw carrot colour to be preserved, which was reflected by good correlations between a* and trans b-carotene content, b* and trans a-carotene content, and hue and total carotenoid content.

An important quality parameter of fried food is the amount of oil uptake, which is incompatible with recent consumer trends towards healthier food. The oil penetration mechanism is not fully understood but study of formulated products is a good way to elucidate the role of the food matrix in oil absorption. In this context, the oil absorption capacity of a restructured matrix, made with native wheat starch and vital wheat gluten, was examined. Four different product formulations were analysed, using 2 levels of gluten content (8% and 12% d.b.) and 2 levels of water content (38% and 44% w.b.). Dough was sheeted into 2 thicknesses (1 and 2 mm) and cut into discs that were either directly fried or fried after predrying with dry air (2 min at 150 °C). Results showed that gluten had a predominant role in the structure, making the dough more elastic and less permeable to oil absorption. High gluten content resulted in lower oil uptake in products with low moisture content. Overall, predried discs absorbed, on average, half of the oil of undried samples. Interestingly, even though predried products with high gluten content had a higher moisture content before frying, they absorbed a low amount of oil, suggesting that oil uptake is not clearly related to the amount of moisture lost but rather to product microstructure.

Vacuum deep-fat frying is a new technology that can be used to improve quality attributes of fried food because of the low temperatures employed and minimal exposure to oxygen. In this paper atmospheric and vacuum frying of apple slices were compared, in terms of oil uptake, moisture loss and color development. In addition, some apple slices were pre-dried (up to 64% w.b.) before vacuum frying to determine the overall effect. To carry out appropriate comparisons between both technologies equivalent thermal driving forces were used in both processes (Δ T = 40, 50, 60 °C), keeping a constant difference between the oil temperature and the boiling point of water at the working pressure. Vacuum frying was shown to be a promising technique that can be used to reduce oil content in fried apple slices while preserving the color of the product. Particularly, drying prior to vacuum frying was shown to give the best results. For instance, when using a driving force of Δ T = 60 °C, pre-dried vacuum fried slices absorbed less than 50% of the oil absorbed by atmospheric fried ones. Interestingly, a strong relationship between water loss and oil content was observed in both technologies, allowing the extension of observations that have been made for atmospheric frying.

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 5 μm) 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.

Changes in the projected area (PA) of particles of an instant coffee powder were followed in real time by videomicroscopy and image analysis. Particles were placed inside a transparent acrylic chamber (7 × 7 × 3 cm) where the relative humidity RH (43%, 52%, 67% and 74%) and temperature T (20, 25 and 30 °C) were controlled and measured in the head space. A “caking index”, ϕ , was defined as the change in PA at any time t with respect to the initial PA. At any temperature, there was an increasing effect in ϕ as RH increased and the shape of ϕ versus time curves closely followed that of caking, measured by sieving techniques. The exponential kinetic model adequately fitted the data. The PA method could be used as a first approximation to predict the tendency to caking of amorphous particles.

Several studies have highlighted the importance of the cooling period in oil absorption in deep-fat fried products. Specifically, it has been established that the largest proportion of oil which ends up into the food, is sucked into the porous crust region after the fried product is removed from the oil bath, stressing the importance of this time interval. The main objective of this paper was to develop a predictive mechanistic model that can be used to understand the principles behind post-frying cooling oil absorption kinetics, which can also help identifying the key parameters that affect the final oil intake by the fried product. The model was developed for two different geometries, an infinite slab and an infinite cylinder, and was divided into two main sub-models, one describing the immersion frying period itself and the other describing the post-frying cooling period. The immersion frying period was described by a transient moving-front model that considered the movement of the crust/core interface, whereas post-frying cooling oil absorption was considered to be a pressure driven flow mediated by capillary forces. A key element in the model was the hypothesis that oil suction would only begin once a positive pressure driving force had developed. The mechanistic model was based on measurable physical and thermal properties, and process parameters with no need of empirical data fitting, and can be used to study oil absorption in any deep-fat fried product that satisfies the assumptions made.

Laser scanning microscopy and fractal analysis were used to determine roughness in the surface of chocolate samples stored under cycling temperature conditions (16 to 26°C) for 24 d. The four samples varied in the source of fat: 100% cocoa butter (CB), lauric and nonlauric fat replacers, and CB with 2% of nonlauric fat replacer. The response variable was the area-scale fractal complexity (Asfc), equivalent to a fractal dimension. Asfc increased with time to an asymptotic value (AV) in much the same way as whiteness index, both being accepted proxies of surface bloom. Images produced from topographical data revealed clearly the increase in roughness. Chocolate samples prepared with CB replacers exhibited an induction period and a slower rate of change in surface roughness than chocolate containing only CB. A linear relationship between a normalized roughness and the square root of time was followed by CB chocolate samples for the period before reaching AV. This result suggests that either diffusion or capillary flow may be the mechanism involved in fat migration to the surface.

Polarised light microscopy was employed non-invasively to monitor lactose crystallisation from non-seeded supersaturated solutions in real time. Images were continuously recorded, processed and characterised by image analysis, and the results were compared with those obtained by refractometry. Three crystallisation temperatures (10, 20 and 30 degrees C) and three different levels of initial relative supersaturation (C/C(s)=1.95; 2.34; 3.15) were investigated. Induction times using the imaging technique proved to be substantially lower than those determined using refractive index. Lactose crystals were isolated digitally to determine geometrical parameters of interest, such as perimeter, diameter, area, roundness and Feret mean, and to derive crystal growth rates. Mean growth rates obtained for single crystals were fitted to a combined mass transfer model (R(2)=0.9766). The model allowed the effects of temperature and supersaturation on crystallisation rate to be clearly identified. It also suggested that, in this set of experiments, surface integration seemed to be the rate controlling step. It is believed that a similar experimental set-up could be implemented in a real food system to characterise a particular process where crystallisation control is of interest and where traditional techniques are difficult to implement.

The optimal physical, chemical and nutritional properties of natural lipids depend on the structure and composition of triacylglycerols. However, they are not always mutually compatible. Lipid modification is a good way to give them specific functionalities, increase their oxidative stability, or improve their nutritional value. As such, chemical and enzymatic interesterification may be used to modify them and produce structured lipids. In accordance, the aim of this study is to compare chemical and enzymatic interesterifi cation of binary blends of fully hydrogenated soybean oil and walnut oil, using sodium methoxide or Lipozyme TL IM, respectively, to produce a fat base with adequate nutritional and physical characteristics. Three different mass ratios of fully hydrogenated soybean oil and walnut oil blends (20:80, 40:60 and 60:40) were interesterified and evaluated. Total interesterification was determined by the stabilization of the solid fat content. Chemical reaction of the 20:80 blend was completed in 10 min and of the 40:60 and 60:40 blends in 15 min. Enzymatically interesterified blends were stabilized in 120 min at all of the mass ratios. Complete interesterification significantly reduced the solid fat content of the blends at any composition. Chemical and enzymatically interesterified fully hydrogenated blend of soybean and walnut oil at mass ratio of 40:60 showed the plastic curve of an all-purpose-type shortening rich in polyunsaturated fatty acids, with a high linolenic acid (C18:3n3) content and with zero trans-fatty acids., Optimalna fizikalna, kemijska i hranjiva svojstva prirodnih lipida ovise o strukturi i sastavu triacilglicerola. Međutim, ona nisu uvijek kompatibilna. Modifikacijom se lipidima daju željena svojstva, te im se povećava oksidacijska stabilnost i hranjiva vrijednost. Za modifikaciju i proizvodnju strukturiranih lipida primjenjuju se kemijska i enzimska esterifikacija. Stoga je svrha ovoga rada bila usporediti kemijsku esterifikaciju mješavine potpuno hidrogeniranog sojinog ulja i orahovog ulja pomoću natrijevog metoksida s enzimskom esterifikacijom pomoću imobilizirane lipaze Lipozyme TL IM, za dobivanje masti optimalnih hranjivih i fizikalnih svojstava. Ispitane su tri različite mješavine hidrogeniranog sojinog ulja i orahovog ulja u omjerima od 20:80, 40:60 i 60:40. Stabilizacija udjela masti označila je završetak esterifikacijskog procesa. Kemijska reakcija mješavine ulja u omjeru 20:80 završena je za 10 min, a ona mješavina u omjerima 40:60 i 60:40 za 15 min. Enzimska je esterifikacija svih triju mješavina ulja završila za 120 min. Potpunom je esterifikacijom bitno smanjen udjel masti u sve tri mješavine ulja. Kemijski i enzimski esterificirane mješavine potpuno hidrogeniranog sojinog ulja i orahovog ulja u omjeru 40:60 imale su krivulju plastičnosti sličnu onoj višenamjenske biljne masti bogate polinezasićenim masnim kiselinama, s velikim udjelom linolenske kiseline (C18:3n3), te bez trans-masnih kiselina.

Recent studies have shown that it should be possible to control lipid bioavailability through food structural approaches. Nevertheless, the gastrointestinal-tract physiological conditions must also be considered. To get a better understanding of this phenomenon, we evaluated the effect of emulsification, as well as the use of sodium caseinate or chitosan, on the postprandial bioavailability of interesterified-lipids in O/W emulsions after oral gastric feeding Sprague–Dawley rats. We verified that emulsification may increase lipid absorption, as determined after feeding sodium-caseinate emulsions. However, this result could not be generalised. Interesterified-lipids that were emulsified with chitosan were equally absorbed as those contained in non-emulsified interesterified-lipids/distilled-water blends.

During the last decade much attention has been given to investigating oil absorption during frying. Several studies have suggested the key role of the dehydrated crust, which is thought to control the main mechanisms in oil absorption, that is drainage and capillary suction during post-frying cooling. To contribute to a better understanding of these mechanisms, we have used infrared microspectroscopy at the Synchrotron Radiation Source at Daresbury (UK) to monitor the oil distribution in fried potato cylinders. We report what we believe to be the first quantitative data on oil distribution within a fried product. Results show that the oil distribution within the crust reflects the anisotropic nature of the porous region in accordance with the proposed mechanism of oil absorption. Pendant ces dernieres decenies, une grande attention a ete donnee a l'etude de l'absorption d'huile pendant la friture. Pour une meilleure comprehension des mecanismes d'absorption de l'huile, cet article rapporte une etude sur l'utilisation de la microspectrometrie infrarouge a haute resolution spatiale pour suivre la penetration de l'huile dans des cylindres de pommes de terre pendant la friture. L'hypothese proposee est que le croute deshydratee joue un role tres important dans l'absorption de l'huile, de drainage et de succion capillaire pendant le refroidissement apres friture.

Summary Frying induces major structural changes in the surface of foods influencing oil uptake. Thiswork discusses the use of several di•erent methods of microscopy as well as techniques ofimage analysis to study frying at the microstructural level. Hot-stage video microscopy wasinstrumental in assessing geometrical changes in cells of potato tissue and in starch in realtime. The swelling of starches inside cells appeared to be retarded compared with that instarch suspensions. Confocal laser scanning microscopy (CLSM) permitted ‘optical’sectioning of the crust, revealing that oil was located in the interior in pockets orsurrounding intact cells. The manipulation of microscopy data by image processing is alsopresented.Keywords Confocal laser scanning microscopy, hot-stage microscopy, image analysis, oil-uptake. IntroductionFrying is an operation used world-wide to createunique flavours and textures in foods. Deep-fat orimmersion frying is a complex process thatinvolves simultaneous heat and mass transfer,resulting in counterflow of water vapour (bubbles)and oil at the surface of the food, physico-chemical alterations of major food componentsand significant microstructural changes (Singh,1995). In fact, desirable characteristics of mostfried foods are derived from the formation of acomposite structure: a dry, crisp and oily outerlayer or crust, and a moist cooked interior or core.The structure of the crust of fried potatoproducts is the result of several alterations, mostof which occur at the cellular and subcellular level.They take place in the outer cell layers of theproduct and the major changes include: physicaldamage owing to cutting (slicing), release ofcontents of broken cells, gelatinization of starchgranules, softening of cell walls, fast dehydrationof tissues and formation and release of vapourbubbles. Microstructural changes in the core aremuch milder and similar to those occurring duringthe cooking of potatoes, the major ones beinghydration and swelling of starch granules andsoftening of the middle lamellae.The importance of microstructural changesduring deep-fat frying has been recognized inmodelling heat and mass transport and unravel-ling their mechanisms. Three of five papers byleading scientists in the field published in anoverview on the frying of foods (Moreira et al.,1995; Rao & Delaney, 1995; Singh, 1995) includedscanning electron microscopy (SEM) photomicro-graphs of fried products, suggesting the import-ance of microstructure. Similarly, Baumann& Escher (1995) recommended that ‘…explana-tions of some factors in the oil uptake still need tobe validated by structure analysis of the potatocrisp in relation to the location of oil depositionand to the mechanism of oil adhesion to thesurface’.Since the first histological studies of deep-fatfried potatoes by Reeve & Neel (1960) evidencehas accumulated that, except for the outermostlayers damaged by cutting, the majority of theinner cells retain their individuality after fryingand contain in their interior dehydrated butgelatinized starch granules. The microstructuralaspect of the core tissue is similar to that of

Vacuum frying was compared with atmospheric frying in the development of wheat starch and gluten based snacks in terms of oil uptake, texture, expansion, and color development. The comparison was based on the concept of equivalent thermal driving force (ETDF) (i.e., keeping a constant difference between the oil temperature and boiling point of water at the working pressure). Vacuum fried snacks were observed to absorb lower oil content at all ETDFs and as low as 27% less of atmospherically fried samples and lighter in color. A very strong relationship existed between texture and oil content on one hand; and expansion and oil content on the other hand for fried matrices from both technologies. SEM was used in validating the result. Vacuum frying can be used for the development of acceptable fabricated fried snacks from wheat starch and gluten with lower oil content and acceptable textural and color properties.

The objective of this research was to study the quality attributes of vacuum and atmospheric dried carrot snacks, as well as their sensory map compared to atmospheric and vacuum fried samples, to understand their potential as a healthy snack. Carrot slices were dehydrated until they reached a water activity of 0.44. Atmospheric drying was done in two-steps (100 °C, 10 min followed by 80 °C, 110 min), whereas vacuum drying (6.5 kPa) was carried out at 60 °C, to provide a product with the required water activity in 2 h, as in atmospheric drying. Vacuum (6.5 kPa) and atmospheric frying were carried out at 98 and 160 °C, respectively. Dried products were compared in terms of color, carotenoids content, Maillard reaction occurrence and texture. A flash-profile test was performed to evaluate sensory attributes of dried and fried snacks. Carotenoids retention and color were similar for atmospheric and vacuum dried products, but, texture was negatively affected in vacuum dried ones. Regarding sensory perception, vacuum inclusion had a better effect in frying compared to drying. As a final point, some instrumental analyzes were successfully related to sensory evaluation, and therefore, could be used as a good proxy in future studies.

Fatty acid (FA) profile is a critical factor in the nutritional properties of fats, but, stereochemistry may also play a fundamental role in the rate and extent to which FAs are absorbed and become available. To better understand this phenomenon, we evaluated the bioavailability of FAs in linseed-oil and palm-stearin blends compared to their interesterified mix, using a sn-1,3 stereospecific lipase, to determine if there was any difference in terms of FA availability when using this technology. Test meals were fed through an intragastric feeding tube on Sprague-Dawley male rats after 18 h fasting. Postprandial blood samples were collected after meal or physiological serum (control) administration and the FA profile of plasma lipids was determined. Results showed that modification of the melting profile through interesterification, without altering the bioavailability determined by sn-2 stereochemistry, could delay lipid absorption at the beginning, but had no effect on total lipid absorption.

Crust microstructure plays a critical role in oil uptake of atmospheric fried food and seems to play an important role in vacuum fried products. The objective of this study was to understand the relationship between key microstructural parameters and oil absorption, after atmospheric and vacuum frying of different vegetable tissues. The effect of drainage and centrifugation in oil-uptake reduction was also analyzed. Key microstructural parameters were determined using gas adsorption at cryogenic temperatures, while oil location and surface roughness were studied using confocal laser scanning microscopy and area-scale fractal analysis, respectively. Overall, we found a linear relationship between porosity and final oil content in vacuum and atmospheric fried chips. However, this relationship could not be extended when analyzing the whole set of data, since oil absorption was significantly higher in atmospheric fried chips. Centrifugation allowed reducing oil-uptake up to 73% in atmospheric fried chips and up to 64% in vacuum fried ones.

Consumers look for products that contribute to their wellness and health, however, even health-conscious consumers are not willing to sacrifice organoleptic properties, and intense full-flavor snacks remain an important trend. The objective of this study was to examine most important quality parameters of vacuum (1.92 inHg) and atmospheric-fried carrot, potato, and apple slices to determine specific advantages of vacuum technology. Slices were fried using equivalent thermal driving forces, maintaining a constant difference between oil temperature and the boiling point of water at the working pressure (ΔT = 60 and 80 °C). This resulted in frying temperatures of 160 and 180 °C, and 98 and 118 °C, for atmospheric and vacuum frying, respectively. Vacuum-fried carrot and potato chips absorbed about 50% less oil than atmospheric-fried chips, whereas vacuum-fried apple chips reduced oil absorption by 25%. Total carotenoids and ascorbic acid (AA) were greatly preserved during vacuum frying. Carrot chips vacuum fried at 98 °C retained about 90% of total carotenoids, whereas potato and apple slices vacuum fried at 98 °C, preserved around 95% of their initial AA content. Interestingly, results showed that the antioxidant capacity of chips may be related to both the presence of natural antioxidants and brown pigments developed at elevated temperatures. Practical Application: A way to reduce detrimental effects of deep-fat frying is through operating-pressure reduction, the essence behind vacuum deep-fat frying. In this way, it is possible to remove product moisture at a low temperature in a low-oxygen environment. The objective of this research was to study the effect of oil temperature reduction when vacuum frying traditional (potatoes) and nontraditional products (carrots and apples) on most important quality attributes (vitamins, color, and oil uptake). Results are promising and show that vacuum frying can be an alternative to produce nutritious and novel snacks with desired quality attributes, since vitamins and color were greatly preserved and oil absorption could be substantially reduced.

The objective of this work is to identify surface topography characterization parameters that are capable of discriminating the surfaces of different fried foods. Three fried food model systems with clearly different surfaces were formulated from vital wheat gluten, native wheat starch, and potato flakes. The surfaces were measured with a scanning laser microscope (SLM), and the ability of several parameters to discriminate between them was tested. Two conventional parameters, the root mean square roughness (Sq) and the surface Kurtosis (Sku), were calculated, along with parameters derived from area-scale fractal analysis: smooth–rough crossover (SRC), fractal dimension, and relative area as a function of scale. The coefficient of variation (COV) of Sq, Sku, and SRC and fractal dimension of different sizes of measurement regions were calculated for the surface of the roughest product in order to specify a measurement region that would be sufficiently large to be representative. The size of the representative region was found to be 25 mm2. Among the parameters evaluated in this study, the most reliable parameter for discriminating the surfaces of fried foods is the relative area calculated from area-scale fractal analysis. SCANNING 32: 212–218, 2010. © 2010 Wiley Periodicals, Inc.

One of the most important quality parameters of fried food is the amount of fat absorbed during the process, which undermines recent consumer trends toward healthier food and low-fat products. In order to obtain a product with a low fat content, it is essential to understand the mechanisms involved during the frying process, so that oil migration into the structure can be minimized. To get such an understanding, this chapter briefly describes the frying process from technological and scientific perspectives. First, it gives a general overview of the frying process and describes the most important quality attributes of fried food. Thereafter, it centers on key nutritional aspects, particularly on the effect of excessive oil consumption on human health, oil degradation, and toxic compounds generation in fried food. Finally, this chapter discusses the most important factors affecting oil absorption, oil absorption kinetics, and different strategies that may be adopted to decrease oil content.

One of the most important quality parameters of fried food is the amount of fat absorbed during the process, which undermines recent consumer trends toward healthier food and low-fat products. In order to obtain a product with a low fat content, it is essential to understand the mechanisms involved during the frying process, so that oil migration into the structure can be minimized. To get such an understanding, this chapter briefly describes the frying process from technological and scientific perspectives. First, it gives a general overview of the frying process and describes the most important quality attributes of fried food. Thereafter, it centers on key nutritional aspects, particularly on the effect of excessive oil consumption on human health, oil degradation, and toxic compounds generation in fried food. Finally, this chapter discusses the most important factors affecting oil absorption, oil absorption kinetics, and different strategies that may be adopted to decrease oil content.

The objective of this article is to assess the effect of different dehydration pretreatments on oil absorption and illustrate how the different ways results can be reported may even drive to opposite conclusions. To do so, potato cylinders were blanched in hot water and dried until a moisture content of 62% (w.b.) by either freeze-drying, air drying, and osmotic drying with a sucrose solution or osmotic drying with a NaCl solution. Control (blanched) and dried potatoes were deep-fat fried at 170 degrees C for time periods between 1 and 5 min. Water removal and total oil uptake were determined and 2 oil fractions were distinguished: superficial oil and penetrated oil. Compared to the control, freeze dried samples increased oil uptake in 15.4% (d.b.) whereas air-dried samples reduced it in 11.2% (d.b.). Similarly, osmotic dehydrated samples showed a high reduction in oil uptake compared to the control (up to 27%[d.b.] when using a sucrose solution). However, this high decrease in oil absorption was attributed to the increase in solids content occurring during the osmotic dehydration process rather than a reduction in the amount of oil taken up. In fact, when the amount of oil absorbed per cylinder was determined, it was verified that oil uptake of osmotically dehydrated samples was even higher than the control, as opposed to what has been previously reported in the literature. These results highlight the importance of selecting an adequate basis to carry out comparisons properly.