Food Biochemistry and Food Processing (2 edition)

BLBS102-c02 BLBS102-Simpson March 21, 2012 11:54 Trim: 276mm X 219mm Printer Name: Yet to Come

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Analytical Techniques in Food Biochemistry

Massimo Marcone

Protein Analysis

Lipid Analysis

Carbohydrate Analysis

Mineral Analysis

Vitamin Analysis

Pigment Analysis

Antioxidants

Gas Chromatography—Mass Spectroscopy

References

Abstract:Food is a very complex heterogeneous “material” com-

posed of thousands of different nutritive and nonnutritive com-

pounds embedded in a variety of different plant and animal matrices.

Nondesirable biochemical compounds such as environmental con-

taminants, microbial and plant toxins, and veterinary drugs are also

present with their presence posing a danger to human health. In

analytical food chemistry, the isolation, identification, and quan-

tification of both desirable and undesirable compounds continue to

pose immense challenges to food analysts. Methods and tests used

to isolate, identify, and quantify must be precise, accurate, be in-

creasing sensitive to satisfy the rigors of investigative and applicable

science, have minimal interfering factors, use minimal hazardous

chemicals, and produce minimal/no hazardous wastes.

This chapter is mainly concerned with the analytical methods

used to determine the presence, identity, and quantity of all com-

pounds of interest in a food. Although it is impossible to address the

quantitative analysis of all food components, the major techniques

used in food analysis will be addressed in detail. The food analyst

has a variety of available tests but the test choice is primarily depen-

dent on the goal of the analysis and the use of the final data. Many of

the traditional analytical biochemical tests such as Kjeldahl diges-

tion for protein determination are still regarded as the gold standard

and is still used in many laboratories.

While useful, traditional analytical methods are continually being

challenged by technological and instrumental developments. Tech-

nology is moving chemical analysis toward the use of more sophis-

ticated instruments (either individually or in tandem) as both instru-

mental specificity and sensitivity are continually being “pushed”

to new limits. Gas chromatography (GC), high performance liq-

uid chromatography (HPLC), spectroscopy including near infrared

(NIR), and mass spectroscopy (MS) are now considered to be basic

laboratory equipment used in food analysis. Tandem hybrid analyti-

cal equipment such as GC-MS is also gradually becoming common

although it is more sophisticated than the single analytical tests.

PROTEIN ANALYSIS

Proteins are a large diverse group of nitrogenous organic com-

pounds that are indispensable constituents in the structure and

function of all living cells. They contribute to a wide variety of

functions within each cell, ranging from structural materials such

as chitin in exoskeletons, hair, and nails to mechanical functions

such as actin and myosin in muscular tissue. Chemically, they

influence pH as well as catalyze thousands of critical reactions,

producing a variety of essential substances that are involved in

functions such as cell-to-cell signaling, immune responses, cell

adhesion, cell reproduction, etc.

Proteins are essentially polymers of 20l-∞-amino acids

bonded together by covalent peptide bonds between adjacent

carboxyl and amino functional groups. The sequence of these

amino acids, and thus the function and structure of the protein,

is determined by the base pairs in the gene that encodes it. These

20 different amino acids interact with each other within their

own chain and/or with other molecules in their external envi-

ronment, which also greatly influences their final structure and

function. Proteins are by definition relatively “heavy” organic

molecules ranging in weight from approximately 5000 to more

than a million Daltons and, over the years, many of these food

proteins have been purified, identified, and characterized. Chem-

ically speaking, nitrogen is the most distinguishing element in

proteins, varying in amounts from 13% to 19% due to the varia-

tions in the specific amino acid composition of proteins (Chang

1998).

Food Biochemistry and Food Processing, Second Edition. Edited by Benjamin K. Simpson, Leo M.L. Nollet, Fidel Toldr ́a, Soottawat Benjakul, Gopinadhan Paliyath and Y.H. Hui.

©C2012 John Wiley & Sons, Inc. Published 2012 by John Wiley & Sons, Inc.

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