Whole Grains Exercise

Question 1

Consider a slice of wholemeal bread and grain bread, Which of these do you think would be considered ‘whole grain’?

Answer 1

DEPENDS ON THE FORMULATION but Both. This is because IF the flour used has the germ and the bran is added to the formulation, then wholemeal bread is considered whole grain

Question 2

The resistant starch from whole grains is RS 1, which means it is protected from
digestion. What do you think protects the starch from digestion?

Answer 2

The starch is protected from digestion by being encapsulated by cell walls in the
endosperm (i.e. the starch is physically protected by the cell walls), or in whole
grains, it is the bran (pericarp of grain) which encapsulates the starch, and prevents
the enzymes from digesting it.

Question 3

What is the definition of whole grain? Think of two examples of different whole
grain foods.

Answer 3

A whole grain is a grain containing 3 parts: bran, endosperm and germ. The
bran is still surrounding the starchy endosperm and the germ has not been
stripped.
eg of different whole grains
- popcorn
- oats

Question 4

In terms of resistant starch or dietary fibre, what is the nutritional problem with
the definition of whole grain?

Answer 4

The definition of resistant starch or dietary fibre is that the starch or fibre
which escapes digestion in the small intestine, enters the large intestine and
is then available for fermentation in the large intestine by the resident
microorganisms. The present definition of whole grains of bran + endosperm
+ germ is not relevant! It’s beyond this – fermentation is the key – i.e.
providing “food”/nutrients for your gut microorganisms!

Question 5

What is the benefit of fermenting starch in our large intestine?

Answer 5

Starch fermentation, in addition to the production of the short chain fatty acids
acetate and propionate, also results in the production of higher than usual
levels of butyrate. Butyrate is a key bioactive which overall promotes colon
health (See figure 9 for specific actions of butyrate).

Question 6

How many types of resistant starch are there?

Answer 6

There are four common types of RS:
RS1 = encapsulated starch 
RS2 = uncooked starch granules
RS3 = retrograded starch
RS4 = chemically modified starch
(RS5 = amylose-lipid complexes - just recently identified)

Question 7

What other carbohydrates do we eat that we need to ferment? Why do we
need to ferment them?

Answer 7

Other carbohydrates include cellulose, arabinoxylans (AX), beta glucans or
mixed-linkage glucans (MLG), and callose.
Our mammalian enzymes cannot digest these carbohydrates, and hence we
rely on our resident gut microbiota enzymes to ferment them when these
dietary fibres enter our large intestine.

Question 8

What is the major problem with storing whole grain foods?

Answer 8

Whole grain foods will contain the bran and germ, in addition to the
endosperm. The bran and germ contain lots of lipids and lipoxygenase
enzymes that easily oxidise lipids into fatty acids, which are volatile and lead
to the “rancid smell” of the grains.

Question 9

What type of compounds lead to rancid aromas? What is the chemical source
of those compounds?

Answer 9

The unsaturated fatty acids (for example, linolenic acid) present in the bran and
germ of whole grains getting oxidised to volatile compounds. These
compounds are aldehydes and ketones.