Gilles Trystram

Deep-fat frying of food: heat and mass transfer, transformations and reactions inside the frying material

Deep-fat frying is a popular process that has been studied essentially to clarify the complex mechanisms of fat decomposition at high temperatures and to assess their effects on human health. The aim of this paper is to show how the application of process engineering methods has recently improved our understanding of the basic principles and mechanisms involved at different scales and different times during the process: pretreatment, frying, and cooling. New results concerning the understanding of the frying process have been obtained as a result of major breakthroughs in on-line instrumentation (heat, steam flux, and local pressure sensors), in the methodology of microstructural and imaging analysis (NMR, MRI, SEM) and in software tools for the simulation of coupled transfer and transport phenomena. Such advances have opened up the way for the creation of a major database of the behavior of various materials and to the development of new tools to control frying operations via final product quality in real conditions. Lastly, this paper promotes an integrated approach to the frying process including various competencies such as those of chemists, engineers, toxicologists, nutritionists, and materials scientists as well as of the catering and industrial sectors.

Fuzzy concepts applied to food product quality control: A review

Fuzzy logic is now a wide field of study and different tools have been developed over the last 10 years. Its implementation in food quality control for the food industry has been highlighted by several authors that have focused on different applications designed specifically for this task. This is especially true in the case of taking into account the reasoning process, expressed in linguistic terms, of operators and experts. Nevertheless, applications are still limited and few reviews on this topic are available. Consequently, the aim of this paper is to provide an overview of the application of fuzzy concepts to the control of the product quality in the food industry over the past 10 years. Future interesting developments and trends in this area are also emphasized.

Characterization of heat and mass transfer during deep-fat frying and its effect on cassava chip quality

Abstract Heat and mass transfer in thin slices of fresh cassava ( Manihot esculenta Crantz) were studied. The frying process was described as two stages involving inner vaporization of mainly high available water, which can be transported inside the material, at temperature around the boiling point and inner vaporization of “bound” water at higher temperature depending on water desorption equilibrium. During the first stage, drying rate was controlled by the serial association of both diffusive and convective thermal resistances. During the second stage, temperature gradients decreased and the core temperature followed the corresponding boiling curve (water desorption curve against boiling temperature). Oil uptake depended on the thermal history of the product, characterized by its final water content. Apparent elasticity modulus and color changes were similar for a same final water content. Boiling curves and core temperature measurement are therefore proposed as a means of predicting the development of chip quality during frying.

Dry sausage ripening control integration of sensory-related properties

A feed-forward control algorithm is proposed to ensure the constancy of the sensory quality of the dry sausage during its fermentation. Fermentation is carried out with industrial equipment. The algorithm is based on human skill: the input variables of the controller are sensory evaluations made close to the line by the operators and the human diagnosis has been modeled using fuzzy logic. An experimental validation is introduced: the results show that the algorithm is likely to be able to control the process so as to obtain the desired sensory characteristics at the end of the fermentation stage. A user interface has been implemented in order to help the operator to cope with process control.

Kinetics of moisture loss and fat absorption during frying for different varieties of plantain

This study compares the behaviour of four varieties of green plantain at their initial stage of maturity during the frying process. A variety traditionally used for the manufacture of thin plantain chips (Dominico Harton commun) and three other varieties found in Latin America (Bouroukou, Bluggoe and FHIA 21) were used. The varieties were characterised by measuring initial moisture content, total sugar content, reducing sugar content, starch content and apparent density. Moisture loss and fat uptake kinetics during frying were assessed at different temperatures (145, 165 and 185°C). With all four varieties, the time required to produce a final moisture content of 40 g kg−1 (wb) was about 90 s at 165°C and 185°C. Use of a lower temperature (145°C) extended the processing time to 150 s. On the other hand, temperature had very little effect on fat content, which proved to be essentially determined by the variety of plantain. Fat content for final water content levels of 40 g kg−1 (wb) ranged from 300 g kg−1 (wb) for Bouroukou to 450 g kg−1 (wb) for Bluggoe regardless of the processing temperature. © 1999 Society of Chemical Industry

Food Engineering at Multiple Scales: Case Studies, Challenges and the Future—A European Perspective

Abstract A selection of Food Engineering research including food structure engineering, novel emulsification processes, liquid and dry fractionation, Food Engineering challenges and research with comments on European Food Engineering education is covered. Food structure engineering is discussed by using structure formation in freezing and dehydration processes as examples for mixing of water as powder and encapsulation and protection of sensitive active components. Furthermore, a strength parameter is defined for the quantification of material properties in dehydration and storage. Methods to produce uniform emulsion droplets in membrane emulsification are presented as well as the use of whey protein fibrils in layer-by-layer interface engineering for encapsulates. Emulsion particles may also be produced to act as multiple reactors for food applications. Future Food Engineering must provide solutions for sustainable food systems and provide technologies allowing energy and water efficiency as well as waste recycling. Dry fractionation provides a novel solution for an energy and water saving separation process applicable to protein purification. Magnetic separation of particles advances protein recovery from wastewater streams. Food Engineering research is moving toward manufacturing of tailor-made foods, sustainable use of resources and research at disciplinary interfaces. Modern food engineers contribute to innovations in food processing methods and utilization of structure–property relationships and reverse engineering principles for systematic use of information of consumer needs to process innovation. Food structure engineering, emulsion engineering, micro- and nanotechnologies, and sustainability of food processing are examples of significant areas of Food Engineering research and innovation. These areas will contribute to future Food Engineering and novel food processes to be adapted by the food industry, including process and product development to achieve improvements in public health and quality of life. Food Engineering skills and real industry problem solving as part of academic programs must show increasing visibility besides emphasized training in communication and other soft skills.

The fuzzy set theory: a helpful tool for the estimation of sensory properties of crusting sausage appearance by a single expert

Automation of visual assessment of foods is a desirable target in quality assurance. We propose an approach based on the theory of fuzzy sets to reproduce, with the help of a camera, the evaluation of sensory properties of a crusting sausage, made close to the manufacturing line (at-line), by a single expert evaluation: the operator. Our study is applied to the assessment of a sausage defect: the crusting. By means of a camera and an adapted image processing, the human evaluation of crusting is reproduced. Good results have been obtained from a database of 76 images.

Deep-fat frying of cassava : influence of raw material properties on chip quality

Thirteen cultivars of cassava (Manihot esculenta Crantz) were used to obtain chips by deep frying slices of fresh cassava flesh in palm oil. The cultivars were representative of three different levels of four major characteristics (water, cyanide, starch and amylose content) in parenchyma. The effects of raw material composition and crop age (10 and 12 months) on mass transfer (dehydration and oil uptake), texture and colour were assessed for 1.5 mm thick chips with a final water content of 0.04 kg kg−1 wet basis, corresponding to a water activity of about 0.3. Frying time varied from 70 to 90 s and oil bath temperature from 140 to 160 °C. All cultivars gave a high frying yield (>0.5 kg chips kg−1 fresh cassava) and a chip fat content of between 0.23 and 0.37 kg kg−1 wet basis, with the highest frying yields and lowest fat contents being obtained from roots with the lowest water content and cyanide content. The intensity of darkening reactions increased in accordance with the level of reducing sugars, while the rigidity modulus of the chips was negatively correlated with the fibre content. The other characteristics (starch, amylose and total sugar content) were either not or poorly correlated with any of the chip quality parameters studied. Cyanoglucosides were only partially eliminated during frying (over 40% retention), so cultivars with a high cyanide content gave bitter chips. For a similar composition, drying rates and cooking rates were much lower when crop age increased. This could be attributed to a structural effect characterising crop age. © 2000 Society of Chemical Industry

Experimental analysis of sensory measurement imperfection impact for a cheese ripening fuzzy model

In the food processes, build tools taking human measurements into account is relevant for the control of the sensory quality of food products. Despite the methodology used to formalize these measurements, these ones are subjected to more imperfections (imprecision, reliability,...). Our aim is to develop tools taking these measurements into account and smoothing the imperfections of these measurements. In this paper, an experimental analysis is led on a fuzzy symbolic model applied to cheese ripening process. This analysis allows to determine the sensory measurements which have the highest impact on the model and to observe the impact of sensory measurements imperfection on the output of the developed fuzzy model.

Application of NADH fluorosensor for on-line biomass measurements in yeast fermentation on whey substrates

Abstract The fluorescence measurement in broth in lactic yeast fermentation on deproteinized whey substrates has been achieved using the new Ingold fluorosensor. Despite the great number of parameters acting upon the fluorescence signal, and particularly dissolved oxygen, this on-line biosensor may provide essential information for batch, fed batch and continuous fermentation control. In batch fermentation, on a pilot plant fermenter, it has been demonstrated that the fluorosensor can be used to precisely estimate the end of the process. This phenomenon can also be used in a fed-batch process. The signal can be related to biomass concentration through a linear correlation. In continuous fermentation, the fluorosensor has been used both in pilot plant and industrial fermenter. It has been shown that it can be reliable to estimate biomass concentration. It is only when substrate flow rate greatly decreases, increasing dissolved oxygen, that the signal diverges. These results open new possibilities of control and optimization of the fermentation process.