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SAM SAGUY, D.Sc.
Institute of Biochemistry, Food Science and Nutrition.
Current Research Projects
Surface chemistry - Wetting of substrates by liquids is a fundamental phenomenon, often characterized by means of contact angle measurement. On real surfaces, which are rough and heterogeneous to some extent, the only measurable value is the apparent contact angle, qap. Moreover, on such surfaces qap depends on the anisotropies of the surface in addition to contact angle hysteresis phenomena. Therefore, reported data at the literature are frequently contradictory. However, mechanical energy, imparted to the liquid by vibration, assists it to overcome the energy barriers, existing on rough surfaces, and hence reaching equilibrium state at the global minimum free energy. The yield value of qap has a thermodynamic meaning and could be, for example, incorporated into Wenzel equation for evaluating the true contact angle. Our objective was to present a method for measuring qap on rough surfaces. This method is based on vertically vibrating the surface in order to allow the drop to reach the global equilibrium state and ensuring its occurrence by measuring drop symmetry from a top view. In order to establish vibration conditions, the effect of drop volume, vibration time and frequency on contact angles values of water, ethylene glycol and phenetol on rough beeswax surfaces, were studied. The criterion for attaining equilibrium state was drop circularity.
Rehydration of food powders - Rehydration is a complex process aimed at the restoration of raw material properties when dried material is contacted with water or water vapor. During dehydration some important changes take place, such as structural and physicochemical modifications that affect the final product quality. Dehydration must preserve quality criteria such as color, nutritional composition, shape or texture, shrinkage of cells, loss of rehydration ability, wettability and case hardening, density and porosity. In products such as instant soups, the additional factors of rehydration capability and velocity must be considered. Consequently, the objective is to obtain products that upon reconstituted would demonstrate adequate textural characteristics, after a very short time. Inappropriate structure and/or composition of the dried material are often the cause for impaired reconstitution properties. The study aims to elucidate the mechanism of rehydration and to determine the pertinent factors affecting its kinetics and derived quality. The Fundamentals of transport phenomena, particularly diffusion, external resistance and relaxation mechanisms governing water uptake during rehydration are also studied. The Weibull distribution model applied in many biological systems is extended for modeling of the rehydration process.
Batter coating - The research focuses on studying the mechanism controlling wetting, and structure formation of coated food undergoing deep fat frying or drying. It combines physical properties of the batter with surface properties. Initial efforts are focused on wetting phenomena. The research targets the implementation of derived quantifiable physical properties data with the understanding of the complex phenomena in order to generate a method or a model which will predict the outcome of marrying the two different but important domains.
Mechanism of oil uptake in deep-fat frying of food systems - Deep fat frying of reconstructed potato products and food systems are investigated. Specific objectives are: To learn the fundamental mechanisms by which oil enters food during deep-fat frying; to develop surface treatments that will reduce this occurrence; and to provide the tools and means to modify the process and/or formulation to significantly reduce fat adsorption during deep-fat frying. The addition of natural food ingredients and their impact on crust formation and reducing fat absorption is also investigated.
Integrated Approach to Deep Fat Frying: Engineering, Nutrition, Health and Consumer Aspects - Deep fat frying is an important, ubiquitous and highly versatile process, which has been used since antiquity to cook a wide spectrum of products. Its unique contribution to sensory characteristics, together with the relatively low cost of large-scale frying, has made fried foods the staples of the ever-growing late 20th-century fast food industry. Despite its considerable fat content and intensified consumers' awareness of the relationships between food, nutrition and health, frying remains a principal cooking method. Oil consumption especially saturated fat is considered a major factor increasing health risks such as coronary heart disease (CHD), cancer, diabetes and hypertension, and even linked to increased causes of deaths. Fried foods contribute a significant proportion of the total fat consumed in the Western world. Yet, a side from their high caloric value, fried foods can be nutritious and favourably compared with other cooking methods such as baking and boiling. Fried foods are popular due to their taste, distinctive flavour, aroma and crunchy texture. Misconceptions about frying extend beyond nutrition to the fundamental aspects of the process, such as the role of water and oil quality during frying. The water released during frying enhances heat transfer, may cause oil deterioration, and also can prevent oxidation. Improving oil quality, the mechanism of oil, coating, engineering considerations of residence time and design, are typical examples of frying technology that are studied.
Porous food structure - Controlling porosity of a porous food product opens a spectrum of possibilities affecting chemical stability, mechanical and structural attributes of foods. Research main objectives are focusing on: engineering cellular solid food systems characterized by a wide range porosity, investigating the relationships between solid content of the wet gel and the derived porosity in the dried cellular solid, stability of typical food system containing fat, nutrients and pigments, and the effect of porosity on sensory, mechanical properties and oxidation of lipids entrapped within the matrix. The effect of porosity and water activity on stability are also investigated.
Paradigm shift for new product development - The Role of Consumer Integration - A paradigm shift is vital in order to successfully cope with the immense risk and the high failure rates of new product development, and the resulting necessary but ever-growing cost. Failure today involves a mind-boggling tag price that has not been reduced in spite of the enormous investments in R&D, consumer research and other product research dimensions. The shift mandates a multidisciplinary team and cross-functional integration of all the development facets including basic R&D, consumer involvement and research, marketing, and management. This paper presents practices currently implemented in new product development, and then furnishes possible explanations for the high failure rate. We present the necessary paradigm shift, and the process "ingredients" required to improve the odds for launching a successful new product. The paradigm shift involves "higher-order" involvement of consumers in the development process. Consumer data drives ongoing development as well as acts as the metric for final acceptance. The paradigm shift meets consumer expectations, and address real and perceived quality attributes. This paradigm shift, defined as "total consumer compliance," is founded on four main pillars: 1) concept development, 2) continual and actionable sensory/consumer inputs, 3) multidisciplinary team with cross-functional integration and 4) close management involvement.
Kinetic models of food quality losses - Kinetic models are developed under typical food process conditions such as high temperature and short time. Shelf-life simulation and prediction. Development of accelerated shelf-life studies and evaluation of a possible extension of the derived model to simulate storage conditions.
[Curriculum Vitae][Current Students][List of Publications]
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