This document discusses several chemical reactions that occur in foods during processing and cooking. It describes the Maillard reaction which creates brown pigments in meats, as well as enzymatic and non-enzymatic browning reactions in fruits and vegetables. It also explains hydrolysis reactions that break down proteins and polysaccharides, altering textures and properties in foods. Various oxidation reactions are outlined as well, which can produce undesirable odors, flavors or discoloration. References are provided at the end for additional information.

1. BASIC FOODS
FOOD SELECTION AND
PREPARATION
Davina Gracia L. Fortunato

2. FOOD
OPhysiological: Any substance which
when taken into the body provides
energy, build and repairs tissues and
regulates body processes.
OBiological: Any substance which
when eaten sustains life and nourishes
the body.

3. OFoods are derived from plants
and animals, both terrestrial
and aquatic.
OFood materials follow a
development process as
illustrated by the changes that
a fruit undergoes before it can
be used as food.

7. CHEMICAL
REACTIONS IN
FOOD

8. MAILLARD REACTION

9. MAILLARD REACTION
OThe Maillard reaction creates brown
pigments in cooked meat in a very
specific way: by rearranging amino
acids and certain simple sugars,
which then arrange themselves in
rings and collections of rings that
reflect light in such a way as to give
the meat a brown color.

10. ENZYMATIC BROWNING

11. OThe purpose of an enzyme in a
cell is to allow the cell to carry
out chemical reactions very
quickly. These reactions allow
the cell to build things or take
things apart as needed. This is
how a cell grows and
reproduces.
ENZYMATIC BROWNING

12. ENZYMATIC BROWNING
OEnzymatic browning
reaction needs oxygen
either from the air or from
intercellular spaces
within the tissue.

13. Obananas turn brown because a
hormone within them triggers the
release of ethylene gas (C2H4).
This accelerates the ripening
processes until the banana
becomes over-ripe.
OEthylene has an accomplice called
polyphenol oxidase (or PPO for
short). It’s found in apples and
potatoes, so leaving your banana
next to an apple will hasten the
ripening process.

14. OXIDATION REACTIONS

15. OIs a reaction that
takes place when
oxygen has access to
products containing
fat or pigments.

16. OIf fats oxidize, they
produce “off” odors and
flavors
OIf pigments oxidize, they
can change color
completely

17. HYDROLYSIS OF PROTEINS
AND POLYSACCHARIDES

18. OProtease is a general term for
enzymes that breakdown
proteins. When a protease
breaks down a protein, the
texture of the food is altered
because the protein will lose its
ability to bind water.

19. OProteases refers to a group
of enzymes whose catalytic
function is to hydrolyze
(breakdown) proteins

20. O Proteins are made up of lots of amino acids joined
together by peptide bonds.
O Hydrolysis of the protein is what happens when the
peptide bonds are broken.
O lysis = splitting; hydro = water
O The result of hydrolysis is smaller amino acid chains
(peptides), and free amino acids.
O The solution containing the protein pieced (small peptide
chains and free amino acids) is called a hydrolysate
solution.

22. OPolysaccharides such as
starch, cellulose, and pectins
are also prone to hydrolysis
with resulting loss in texturing
ability. Starch will lose its
gelling properties when
hydrolyzed.

23. O http://www.scienceweek.ie/chemistry-of-
cooking.html
O http://www.britannica.com
O DE LEON, S.Y. et al. 1999. Basic Foods
for Filipinos 3rd Edition. Merriam and
Webster Inc., Metro Manila, Philippines.