Nutritional Chemistry Basics

Food Chemistry and Nutrition - Fall 2024

• This course covers food chemistry and nutrition.
• The course instructor is Dr. Nizam Diab.
• A syllabus for the fall 2024 semester is provided.

Chapter 1: Overview of Food Constituents and Their Role

• Food chemistry is defined as the study of the chemical processes and interactions of all biological and non-biological components of foods.
• It's similar to biochemistry, focusing on carbohydrates, lipids, proteins, vitamins, minerals, enzymes, additives, flavors, and colors.
• It also investigates changes in food during processing and methods to enhance or avoid these changes.
• A product's composition and structure influence how it behaves in food systems.
• Food nourishes the body and is essential for life, growth, and repair.
• Diet is composed of the foods and beverages one consumes.

Introduction to Food Chemistry and Nutrition

• Most organized nutrition studies focused on the 20th century.
• Hippocrates (400 BC) considered food as a universal nutrient.
• Antonie Lavoisier (18th century), a French Chemist, is known as the father of nutrition.
• The Qur'an and Hadith contain many verses associated with food and nutrition.
• Modern science has confirmed some of these facts and not others.

Definition and Importance of Food Chemistry

• Food consists of products derived from plants or animals and provides energy and nutrients.
• Food is crucial for maintaining life, growth, and tissue repair.
• The chemical substances in food are called nutrients; over 50 different types exist categorized into six groups.

What is a Nutrient?

• Nutrients help maintain the body by providing energy, structural materials, and regulating agents for growth, repair, and disease reduction.

Macronutrients & Micronutrients

• Macronutrients (needed in large amounts) include carbohydrates, proteins, and fats.
• Micronutrients (needed in smaller amounts) include vitamins and minerals.

Calories per Gram

• Protein: 1 gram = 4 calories
• Carbohydrates: 1 gram = 4 calories
• Fat: 1 gram = 9 calories

Water

• Water aids digestion, cell growth, and maintenance.
• Water facilitates chemical reactions and lubricates joints and cells.
• Water regulates body temperature

Fats

• Fats supply energy, carry fat-soluble vitamins, and protect organs.
• Different types of fats exist, including saturated (dairy, meat, etc.), unsaturated (fish, nuts, etc.), and cholesterol (found in cells).

Proteins

• Proteins build and repair muscles and cell tissues.
• Proteins help create important substances in the body and regulate body processes.
• Complete proteins include dairy, eggs, fish, meat, and poultry.
• Incomplete proteins include beans, grains, and nuts.

Vitamins

• Vitamins are divided into fat-soluble and water-soluble groups.
• Fat-soluble vitamins dissolve in fats and are stored in the body fatty tissues.
• Water-soluble vitamins dissolve in water and are not stored in the body.

Minerals

• Minerals are essential for the body's function at different levels.
• Include listed minerals and their atomic numbers and masses.
• Sources of listed minerals are given.

Water Activity in Food

• Water is crucial in food production, as a carrier for nutrients, and for cleaning.
• Water can transmit diseases, contaminate food, and impact food properties during processing.
• Water activity is the ratio of food water vapor to pure water vapor, impacting chemical reactions and microbial growth.
• Water activity can be controlled via different additives, packaging, and storage.

Importance of Water Activity in Foods

• Water activity indicators are important for predicting the growth of bacteria, yeasts, and molds.
• Water activity is vital for foods to safely store without refrigeration.

Food for Thought

• Be mindful of excess vitamins and minerals.
• Variety in food is important.
• Water intake is critical for good health.
• Daily exercise is important.
• Consult a doctor or nutritionist before using supplements.

Role of Water and Water Activity in Food

• Food production and processing require significant water amounts.
• Water can cause significant disease outbreaks in developed and developing countries.
• Water can contaminate foods during primary production, impacting food-borne illness transmission.

In Food Processing and Preservation

• Large volumes of water are required for food processing tasks.
• Water impacts chemical reactions and physical changes during food processing.

Role of Water and Water Hardness

• Water hardness affects pH balance, influencing food processing, particularly clear beverage production.
• Water activity in foods can be controlled via additives, packaging, and storage.

The Importance of Water Activity in Foods

• Water activity indicates the amount of available water to microbes.
• Each microorganism has a minimum water activity for growth.
• Controlling water activity can impact shelf life without refrigeration.

Chemical Stability

• Water activity is important for the chemical stability of most foods, including those with carbohydrates and proteins.
• The Maillard reaction (browning) affects foods with increasing water activity, peaking between 0.6–0.7.
• Water activity strongly affects the spontaneous breakage of fat molecules, causing rancidity.

Enzymatic Stability

• Enzymatic reactions are slowed at low water activity; however, heat treatment in processed foods significantly reduces the importance of enzymatic spoilage.

Challenges and Role of Food Chemistry

• Food chemistry helps produce healthier foods that still taste good.
• Food chemistry allows for control over food processes, leading to better quality products with longer shelf lives.

Chapter 2: Major Food Constituents - Properties and Interactions

• This chapter will discuss the components affecting food properties and interactions.

Nutrients Divided into Two Categories

• Macronutrients: Carbohydrates, proteins, and fats; significantly provide energy to the body.
• Micronutrients: Vitamins and minerals; essential in smaller amounts for various bodily functions.

Carbohydrates

• Carbohydrates are the most widely distributed and abundant organic compound on Earth.

• Carbohydrates provide energy and serve as precursors for aromas, colors (especially during thermal processing), and non-digestible bulking materials.

• Numerous subcategories of carbohydrates are explained, with detailed chemical properties and functions.

Monosaccharides and their Chemical Properties

• Monosaccharides (simple sugars) are well-crystallized solids, soluble in water, and generally sweet.
• They are classified by the placement of the carbonyl group (aldose or ketose) and the number of carbon atoms (triose, tetrose, pentose, hexose, etc.).
• Detailed classification and examples of various sugars are included.

Classification of Monosaccharides

• Based on the carbon count and the placement of the carbonyl group, they are classified as aldotrioses, aldotetroses, aldopentoses, aldohexoses, ketotrioses, ketotetroses, ketopentoses, and ketohexoses, etc.

Examples of Hexoses and Pentoses

• Table of examples of hexoses and pentoses from carbohydrates in the discussion, including D-glucose, D-galactose, D-xylose, and D-ribulose.

Cyclic Monosaccharide Conformation

• Monosaccharides in crystalline forms exist as ring structures, called tautomers.

Chemical Properties of Monosaccharides

• Monosaccharides undergo redox reactions to form sugar alcohols and sugar acids.
• Hydrogenation of glucose, galactose, or mannose produces sorbitol, dulcitol, and mannitol, respectively.
• Oxidation generates aldonic, aldaric, and uronic acids, respectively. Chemical reactions are explained with structural formulas.

Oligosaccharides

• The oligosaccharides include disaccharides, trisaccharides, and tetrasaccharides, determined by the number of monosaccharide units in their structure.
• Includes sucrose, lactose, and maltose as the most significant examples.
• Sucrose is commonly found in plant juices—like sugarcane, sorghum, beet, and apples.
• Sucrose consists of glucose and fructose linked together.
• Hydrolysis of sucrose produces glucose and fructose, altering rotation effects, resulting in invert sugar formation.
• Honey often contains a substantial fraction of invert sugar.
• Lactose is a reducing sugar formed from the linkage between β-D-galactose and α-D-glucose.
• Hydrolysis of lactose produces glucose and galactose.
• Maltose consists of two glucose molecules linked together by an α linkage.
• It is a product of starch hydrolysis and is hydrolyzed into glucose by the enzyme maltose.
• Raffinose is a trisaccharide containing fructose, glucose, and galactose, prevalent in sugar beet and molasses.

Functional Properties of Sugars (including sugar alcohols)

• Simple and complex carbohydrates are widely used to meet diverse functional requirements.
• Chemical structures and interactions with other molecules in food are crucial to understanding how these ingredients will behave physiochemically in food systems.
• Properties like sweetness, mouth feel, solubility, etc. of sugars and sugar alcohols also affect food systems.
• Detailed discussion of how structures and interactions affect functional properties of specific sugars are observed.

Sugars and Sweeteners

• Sucrose, invert sugar, corn syrups, and honey are common sugar-containing food ingredients.
• Sucrose, composed of glucose and fructose, is known for its versatility in altering between amorphous and crystalline states.
• Invert sugar is less likely to crystallize and has higher hygroscopic characteristics.
• The use of sucrose and invert sugar varies in ice cream, baked goods, intermediate-moisture foods, and soft drinks.

Sugar Alcohols

• All sugars can be hydrogenated into their corresponding polyols, but food applications are limited.
• Polyols, with high humectancy and plasticizing properties, improve food texture and moisture content.
• Polyols show low reactivity to aldehyde/ketone groups and don't easily undergo Maillard reactions.
• Polyols’ negative heat of solution contributes to a cooling sensation in the mouth.
• Examples include sorbitol, mannitol, and xylitol, which can replace sucrose and glucose in diabetic diets without significantly altering blood glucose levels.
• Sorbitol is also found in meat products, sauces, mayonnaise, chewing gums, and confectioneries.
• Sorbitol helps preserve fish products and improve ice cream texture.

Polyssacharides.

• Carbohydrates consisting of ten or more monosaccharide units, linked through glycosidic links—examples include starch and cellulose and hemicelluloses.
• Can be categorized as homo-polysaccharides, if they have a single type of monosaccharide constituent, and hetero-polysaccharides if they have more than one type of constituent.
• Starches, cellulose, alginates, carrageenans, agar, furcellaran, plant gums, seed gums, microbial gums, and pectins are examples in foods.
• Food functions, influences structure, texture, water binding, and overall sensory properties in diverse ways.
• Specific examples of polysaccharides and their properties are discussed, detailing their functions in foods.

Functional Properties of Polysaccharides

• Function properties are observed in terms of thickening, emulsification, stabilization of emulsions and foams, flow and texture properties, softness retention, browning, fermentation, control of microbial and enzyme modification and stabilization of taste and flavor in food.
• Modifications affect the components' properties, such as molecular weight, configuration, carbonyl and hydroxyl groups, and sulfated ester groups.

Modified Starches and Their Applications

• Native starches may lack specific functional properties for food applications.
• Modifying these starches through physical or chemical methods produces starches with tailored properties, used in various applications.
• Pregelatinized starches, acid-hydrolyzed starches, oxidized starches, and cross-linked starches are modified forms, each with unique advantages in food processing.
• Pregelatinized starches are beneficial for convenience foods, like instant puddings and sauces.
• Acid-hydrolyzed starches facilitate better gel-forming properties, suitable for different applications (like gum jellies and orange slices).
• Oxidized starches enhance clarity and intermediate viscosity gels, improving the applications of starch batters to fish and meat.
• Crosslinked starches enhance starch granule cohesion in high temperature environments.

Resistant Starch

• This is a fraction of starch and hydrolysis products, resisting digestion and absorption by healthy individuals.
• Three Types: Physically trapped, resistant granules, and retrograded.
• Formation depends on starch structure, processing environment, and storage conditions.
• Properties and their effect on human health are elaborated.

Physiological Significance

• The starch not absorbed in the small intestine undergoes fermentation by the microflora in the large intestine.
• Fermentation of resistant starch produces short-chain fatty acids, like acetate, propionate, and butyrate.
• These fatty acids are believed to be protective in large bowel cancer due to their effects on the pH and enzyme activity.
• Resistant starches can affect fecal bulking, thus contributing to the dilution of fecal carcinogens.
• Detailed physiological effects and benefits of resistant starch are highlighted.

Factors Affecting Resistant Starch Formation

• The formation of resistant starch is impacted by starch structure, processing, and storage conditions.
• Conditions limiting moisture or heat may allow retention of the native crystal structure of starch granules.

Functional Properties of Resistant Starch

• Resistant starch's functional properties provide diverse benefits to food applications, including improved fiber content, functionalities, and overall product quality improvement, all discussed in detail.

Selection of an Optimum Starch for Snack Development

• Development of functional starches for snack foods depends on considerations of texture, shape, color, and desired functionality.
• Different types of modified starches are used (and their properties) to provide specific characteristics in various snack applications.

Baked Snacks

• Baking involves development of structural properties of the product.
• Pregelatinized starches, cold-water swelling starches, are beneficial for slow heating, improving texture, and reducing cracking.
• Modifying starches that mimic fat reduces cracking issues in baked goods.
• Details about preferred starch types for specific characteristics in baked goods are added.

Fried Snacks

• Frying dehydrates food products, creates a unique texture, and impacts product color and time.
• Modifications to starches can improve texture, prevent disruption of granules and improve mouthfeel, reduce oil absorption during frying, and overall product quality.
• Detailed information about the application of different types of starch (including waxy corn and high amylose) is added.

Extruded Snacks

• Combined moist starchy ingredients are heated and sheared under pressure to produce extruded snacks.
• Manipulation of starch types and ratios impacts the final texture.
• Cross-linked starches will have higher viscosity, a smoother texture, and less expansion.
• The use of high amylose starches provides firmness and crunchiness, while high amylopectin starches result in a softer and expanded product.
• Specific starch types (and their properties) are elaborated.

Film Forming, Sheen Protection, and Bonding

• Specialty starch-based powders create films on foods, enhancing sensory characteristics for various applications.
• Films can be used to bind flavors, add sheen, and prevent breakage in transport or during handling of snacks.
• Elaborated descriptions and applications of specialty starches in enhancing film formation and resulting properties are explained.