Heribert Watzke

Influence of Surfactants on Lipase Fat Digestion in a Model Gastro-intestinal System

In the present study, we use a model gastro-intestinal system to study the influence of different food-grade surface-active molecules (Sn-2 monopalmitin, β-lactoglobulin, or lysophosphatodylcholine) on lipase activity. The interfacial activity of lipase and surfactants are assessed with the pendant drop technique, a commonly used tensiometry instrument. A mathematical model is adopted which enables quantitative determination of the composition of the water–oil interface as a function of bulk surfactant concentration in the water–oil mixtures. Our results show a decrease in gastric lipolysis when interfacially active molecules are incorporated into a food matrix. However, only the Sn-2 monopalmitin caused a systematic decrease in triglyceride hydrolysis throughout the gastro-intestinal tract. This effect is most likely due to exclusion of both lipase and triglyceride from the water–oil interface together with a probable saturation of the solubilization capacity of bile with monoglycerides. Addition of β-lactoglobulin or lysophopholipids increased the hydrolysis of fat after the gastric phase. These results can be attributed to an increasing interfacial area with lipase and substrate present at the interface. Otherwise, β-lactoglobulin, or lysophopholipids reduced fat hydrolysis in the stomach. From the mathematical modeling of the interface composition, we can conclude that Sn-2 monopalmitin can desorb lipase from the interface, which, together with exclusion of substrate from the interface, explains the gradually decreased triglyceride hydrolysis that occurs during the digestion. Our results provide a biophysics approach on lipolysis that can bring new insights into the problem of fat uptake.

Impact of processing on bioavailability examples of minerals in foods

Bioavailability is key to the effectiveness of functional foods. Among functional food components minerals have a key function in their essential role for a healthy life. Deficiencies in essential minerals are seen as a major nutritional problem in the world today. This review investigates the impact of food processing on the bioavailability of minerals. The findings of the last decade clearly show that there is no simple relation between food processing and bioavailability. Processing can have a positive impact through separation or partitioning of minerals (enrichment), or through the destruction of inhibitors or, the beneficial complex formation between food components and metal ions, thereby enhancing their availability. However, the impact can also be negative by deactivating enzymes that degrade inhibitors or by generating insoluble metal compounds (e.g. oxidation, precipitation). Potential for the modulation of bioavailability will arise when the speciation of metal ions and their fate in processing and in the body are better understood.

Competition between lipases and monoglycerides at interfaces

Tensiometry (the pendant drop technique), interfacial shear rheology, and ellipsometry have been used to study the effect of polar lipids that are generated during fat digestion on the behavior of lipases at the oil-water interface. Both Sn-1,3 regiospecific and nonregiospecific lipases have been used, and a noncatalytically active protein, beta-lacloglobulin, has been used as reference in the interfacial shear rheology experiments. The results from the pendant drop measurements and the interfacial rheology studies were in agreement with each other and demonstrated that the Sn-2 monoglyceride, which is one of the lipolysis products generated when a Sn-1,3 regiospecific lipase catalyzes triglyceride hydrolysis, is very interfacially active and efficiently expels the enzyme from the interface. Ellipsometry conducted at the liquid-liquid interface showed that the lipase forms a sublayer in the aqueous phase, just beneath the monoglyceride-covered interface. Sn-1/3 monoglycerides do not behave this way because they are rapidly degraded to fatty acid and glycerol and the fatty acid (or the fatty acid salt) does not have enough interfacial activity to expel the lipase from the interface. Since the lipases present in the gastrointestinal tract are highly Sn-1,3 regiospecific, we believe that the results obtained can be transferred to the in vivo situation. The formation of stable and amphiphilic Sn-2 monoglycerides can be seen as a self-regulatory process for fat digestion.

Adsorption of polar lipids at the water-oil interface.

Dietary fat has long been recognized as an essential component in nutrition. However, most of the lipids present in food need to be converted into more bioavailable compounds. Lipases have a crucial role in converting triglycerides into more polar lipids with increased water solubility and a tendency to form micelles. However, the surface active molecules generated by lipolysis may have a detrimental effect on the interfacial biocatalysis. In the present work we evaluate the interfacial properties of lipase-generated molecules during fat digestion. By using the pendant drop technique we assessed the amphiphilic character of fatty acid salts, monoglycerides, and diglycerides as individual surfactants and mixtures. The experimental results are fitted with a mathematical model, which assists in the determination of the interfacial properties of the surfactants. Our results show that monoglycerides have considerably higher interfacial activity than fatty acid salts and diglycerides. Therefore, the interface will soon be dominated by monoglycerides. The pH dependency of the interfacial activity of fatty acids is also explored in the current work. We believe that our results can contribute to a better understanding of the complex interfacial phenomena occurring during fat digestion.

Bioinformatics and data knowledge: the new frontiers for nutrition and foods

The recent publication of the Human Genome poses the question: how will genome technologies influence food development? Food products will be very different within the decade with considerable new values added as a result of the biological and chemical data that bioinformatics is rapidly converting to usable knowledge. Bioinformatics will provide details of the molecular basis of human health. The immediate benefits of this information will be to extend our understanding of the role of food in the health and well-being of consumers. In the future, bioinformatics will impact foods at a more profound level, defining the physical, structural and biological properties of food commodities leading to new crops, processes and foods with greater quality in all aspects. Bioinformatics will improve the toxicological assessment of foods making them even safer. Eventually, bioinformatics will extend the already existing trend of personalized choice in the food marketplace to enable consumers to match their food product choices with their own personal health. To build this new knowledge and to take full advantage of these tools there is a need for a paradigm shift in assessing, collecting and sharing databases, in developing new integrative models of biological structure and function, in standardized experimental methods, in data integration and storage, and in analytical and visualization tools.

RELEASE OF VOLATILES FROM CUBIC PHASES: MONITORING BY GAS SENSORS

Abstract Structured fluids such as emulsions and liquid crystalline mesophases can be used to control aroma release This study shows that the use of a gas sensor array coupled with pattern recognition analysis can be particularly useful in studying volatile profiles A mixture of 8 carefully selected volatile, hydrophilic and hydrophobic compounds was entrapped in 4 different matrices: water, lipids (sunflower oil, unsaturated monoglycerides), emulsion (20% wt water) and cubic phases (20 and 3% wt water) A clear discrimination between the release pattern of the different matrices has been measured by the sensor array system. It has been shown that the cubic phase release patterns is not only controlled by its composition but also depended strongly on ihe lipid/water interfacial area The combined use of structured fluids (structure-release relationship) and sensor arrays allows to control and to distinguish the release patterns of volatile.

The Nutrient Balance Concept: A New Quality Metric for Composite Meals and Diets

Background Combinations of foods that provide suitable levels of nutrients and energy are required for optimum health. Currently, however, it is difficult to define numerically what are ‘suitable levels’. Objective To develop new metrics based on energy considerations—the Nutrient Balance Concept (NBC)—for assessing overall nutrition quality when combining foods and meals. Method The NBC was developed using the USDA Food Composition Database (Release 27) and illustrated with their MyPlate 7-day sample menus for a 2000 calorie food pattern. The NBC concept is centered on three specific metrics for a given food, meal or diet—a Qualifying Index (QI), a Disqualifying Index (DI) and a Nutrient Balance (NB). The QI and DI were determined, respectively, from the content of 27 essential nutrients and 6 nutrients associated with negative health outcomes. The third metric, the Nutrient Balance (NB), was derived from the Qualifying Index (QI) and provided key information on the relative content of qualifying nutrients in the food. Because the Qualifying and Disqualifying Indices (QI and DI) were standardized to energy content, both become constants for a given food/meal/diet and a particular consumer age group, making it possible to develop algorithms for predicting nutrition quality when combining different foods. Results Combining different foods into composite meals and daily diets led to improved nutrition quality as seen by QI values closer to unity (indicating nutrient density was better equilibrated with energy density), DI values below 1.0 (denoting an acceptable level of consumption of disqualifying nutrients) and increased NB values (signifying complementarity of foods and better provision of qualifying nutrients). Conclusion The Nutrient Balance Concept (NBC) represents a new approach to nutrient profiling and the first step in the progression from the nutrient evaluation of individual foods to that of multiple foods in the context of meals and total diets.

Lipase-catalyzed Reactions at Interfaces of Two-phase Systems and Microemulsions

This work describes the influence of two polar lipids, Sn-1/3 and Sn-2 monopalmitin, on the activity of lipase in biphasic systems and in microemulsions. In previous communications, we have shown that Sn-2 monoglycerides can replace Sn-1,3 regiospecific lipases at the oil–water interface, causing a drastically reduced rate of lipolysis. We here demonstrate that even if the lipase is expelled from the interface, it can catalyze esterification of the Sn-2 monoglyceride with fatty acids in both macroscopic oil–water systems and in microemulsions, leading to formation of di- and triglycerides.

Chapter 5:Self-Assembled Liquid Particles: How to Modulate their Internal Structure

In the modern type of food formulation, it is of increasing importance to have the essential components arranged in such a way that their functionality and bioavailability are optimized. This must be achieved and understood on the molecular level. Thus, self-assembly is a central mechanism for effic...

Chapter 2:Self-Assembly in Food – A New Way to Make Nutritious Products

For many years food manufacturers have been trying to meet the rising expectations of consumers for nutritionally balanced and healthy foods. The current way to address this challenge is to ‘enhance’ nutritional functionality within a product by adding to a common food base various bioactives such a...