Handbook of Food Science and Technology 1

Food Alteration and Food Quality

Romain Jeantet, Thomas Croguennec, Pierre Schuck, Gérard Brulé, Romain Jeantet, Thomas Croguennec, Pierre Schuck, Gérard Brulé

• Publisher: Wiley-ISTE
• Year: 2016
• Print ISBN: 9781848219328
• eBook ISBN: 9781119268673
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Food Science
• Index: Technology & Engineering

This book serves as a general introduction to food science and technology, based on the academic courses presented by the authors as well as their personal research experiences.

The authors' main focus is on the biological and physical-chemical stabilization of food, and the quality assessment control methods and normative aspects of the subsequent processes.

Presented across three parts, the authors offer a detailed account of the scientific basis and technological knowledge needed to understand agro-food transformation. From biological analyses and process engineering, through to the development of food products and biochemical and microbiological changes, the different parts cover all aspects of the control of food quality.

PART 1
Water and Other Food Constituents

1
Water

Water is the most abundant constituent of the majority of foods. It therefore plays a crucial role in the physicochemical characteristics and properties of the plant and animal foods we eat. These characteristics can be desired due to their contribution to food quality (the texture of fruit, vegetables and meat, which depends, among other things, on cell turgidity as well as on specific and complex interactions between water and other constituents). However, they can also contribute to food spoilage through biochemical and microbiological processes. As a result, several food preservation methods are based, at least partially, on lowering the water activity (a_w) or the water availability.

1.1. Structure and state of water

The water molecule, composed of two hydrogen atoms and one oxygen atom (H₂O), can exist, like many substances, in three different states: solid, liquid or gas.

In the liquid and vapor state, the water molecule is a polar monomer (see Figure 1.1).

In the solid state (i.e. ice), water molecules are linked by hydrogen bonds and form a crystalline polymer in which each monomer molecule is connected to four other molecules by hydrogen bonds. The distance between two oxygen atoms is 0.276 nm. At temperatures below −173°C, all hydrogen atoms are involved in hydrogen bonds, whereas at 0°C only around 50% are involved, and at 100°C only a small percentage are involved.

Figure 1.1. Water molecule

Certain water properties can be attributed to these intermolecular bonds, in particular the boiling point, melting point, latent heat of fusion, latent heat of vaporization, specific heat, surface tension and the dielectric constant. However, water in a liquid state behaves like a monomer in terms of viscosity and the diffusion coefficient (Tables 1.1 and 1.2).

Table 1.1 Properties of water

Properties	Unit	Value
Molar mass	g mol^–1	18.01528
Melting point (at 101,325 Pa)	°C	0.00
Boiling point (at 101,325 Pa)	°C	100.00
Maximum density	kg m^–3	999.95
Temperature of maximum density	°C	4.00
Triple-point temperature	°C	0.01
Triple-point density (liquid)	kg m^–3	999.78
Triple-point density (gas)	10^−3 kg m^–3	4.88
Latent heat of sublimation at the triple point	10^3 J kg^–1	2800
Critical temperature	°C	373.99
Critical pressure	MPa	22.064
Critical density	kg m^–3	322
Specific volume at the critical point	10^−3 m^3 kg^–1	3.11
Latent heat of freezing at 0°C	10^3 J kg^–1	335

Different theoretical models have been proposed to explain the liquid and solid state behavior of water. Monomers as well as higher-energy molecules exist in a static equilibrium: each molecule is involved in one to four hydrogen bonds; the latter can form short-lived labile clusters.

Table 1.2. Properties of water

Properties	Units	Frozen water		Liquid water						Water vapor
Temperature	(°C)	–20	0	0	20	40	60	80	100	100	200
Density	kg m^–3	919.3	916.8	999.8	998.2	992.2	983.2	971.8	958.4	0.589	0.452
Viscosity	10^–6 Pa s	–	–	1,793	1,002	653	466	354	281	12.5	16.4
Surface tension	10^–3 N m^–1	–	–	75.64	72.75	69.60	66.24	62.67	58.91	–	–
Vapor pressure	(Pa)	103.4	611.3	611.3	2,338.8	7,381.4	19,932	47...

Table of contents

• Cover
• Table of Contents
• Title
• Copyright
• Introduction
• PART 1: Water and Other Food Constituents
• PART 2: Food Modifying Agents and Mechanisms
• PART 3: Quality Control and Assessment
• Bibliography
• List of Authors
• Index
• End User License Agreement