Course:Grain Quality

1
Course Grain Quality Module 6 Determining
the Chemical Characteristics of Milled
Rice Lesson 1 What are the three chemical
characteristics of milled rice that determine
quality?
Gel consistency measures the tendency of the
cooked rice to harden on cooling.
Gelatinization temperature determines the time
required for cooking the rice
High amyclose content? Rice grains cook dry, are
less tender, and become hard upon
cooling. Low-amylose content? Rice grains cook
moist and are sticky
2
Course Grain Quality Module 6 Determining
the Chemical Characteristics of Milled
Rice Lesson 1 What are the three chemical
characteristics of milled rice that determine
quality?
FREQUENTLY ASKED QUESTIONS (FAQs)

1. What are the specific physicochemical tests used
   to determine the cooking and eating qualities of
   rice?

• Alkali test
• Amylose test
• Gel consistency test
• Kernel elongation test
• Aroma test

3
Course Grain Quality Module 6 Determining
the Chemical Characteristics of Milled
Rice Lesson 1 What are the three chemical
characteristics of milled rice that determine
quality?
FREQUENTLY ASKED QUESTIONS (FAQs)

1. Why is endosperm appearance a major breeding
   consideration?

The appearance of milled rice is important to the
consumer, which makes it also important to the
producer and the miller. The consumer prefers
rice with a clear endosperm and pays a premium
rice for it, even though capacity disappears
during cooking and does not affect eating
quality. Grain with opaque areas in the
endosperm, caused by the loose packing of the
starch and protein particles, breaks more readily
during milling than clear grain, greatly reducing
its market value.
4
Course Grain Quality Module 6 Determining
the Chemical Characteristics of Milled
Rice Lesson 1 What are the three chemical
characteristics of milled rice that determine
quality?
FREQUENTLY ASKED QUESTIONS (FAQs)

1. Of what importance are grain length, shape and
   endosperm appearance to the breeder?

Most breeders attempt to estimate the milling
behavior of pedigree selections n the basis of
grain length and shape and on endosperm
appearance. Grain traits that contribute to
increased breakage, singly and in combination
with other traits, include grain length,
excessively slender or bold shape, partial
flatness, and appreciable white belly.
5
Course Grain Quality Module 6 Determining
the Chemical Characteristics of Milled
Rice Lesson 1 What are the three chemical
characteristics of milled rice that determine
quality?
FREQUENTLY ASKED QUESTIONS (FAQs)

1. How does the limited association of gelanization
   temperature and amyclose content help the
   breeders?

It allows the breeders, in certain cases, to use
the simple gelatinization temperature test to
estimate the amylose content, which is
considerably more difficult to measure directly.
6
Course Grain Quality Module 6 Determining
the Chemical Characteristics of Milled
Rice Lesson 1 What are the three chemical
characteristics of milled rice that determine
quality?
FREQUENTLY ASKED QUESTIONS (FAQs)

1. How is gelatinization temparature related to the
   physical cooking properties of rice?

Gelatinization temperature directly affects the
physical properties of the starch granule, which
in turn influences the quality ratings of cooked
rice. Rice with a high gelatinization temperature
becomes excessively soft and tends to
disintegrate when overcooked. Under standard
cooking procedures, this type of rice tends to
remain undercooked. It requires more water and
time to cook than those with low or intermediate
gelatinization temperature. Thus, gelatinization
temperature correlates positively with the time
required to cook rice. Soaked milled rice of high
gelatinization temperature elongates less during
cooking than rices with low or intermediate
gelatinization temperature.
7
Course Grain Quality Module 6 Determining
the Chemical Characteristics of Milled
Rice Lesson 1 What are the three chemical
characteristics of milled rice that determine
quality?
FREQUENTLY ASKED QUESTIONS (FAQs)

1. Why test for gel consistency?

• Varietal differences in gel consistency exist
  among varieties of similar high amylose content
  (more than 25). The gel consistency test
  separates the high-amylose rices into three
  categories
• very flaky rices with hard gel consistency
  (length of gel 40 mm or less)
• flaky rices with medium gel consistency (length
  of gel 41 to 60 mm)
• soft rices with medium gel consistency (length of
  gel gt 61 mm).

8
Course Grain Quality Module 6 Determining
the Chemical Characteristics of Milled
Rice Lesson 1 What are the three chemical
characteristics of milled rice that determine
quality?
FREQUENTLY ASKED QUESTIONS (FAQs)

1. Why should paddy rice be stored for at least 4
   months after harvest before tasting panels
   evaluate promising lines?

Aging increases water absorption and volume
expansion during cooking, resulting in a more
flaky cooked rice than freshly harvested grains.
9
Course Grain Quality Module 6 Determining
the Chemical Characteristics of Milled Rice
Lesson 2 Why is amyclose content important
and how is it measured?
If then
Amylose content is high, the rice grains will show high volume expansion (not necessarily elongation) and a high degree of flakiness. The rice grains cook dry, are less tender, and become hard upon cooling.
Amylose content is low, the rice grains will cook moist and sticky.
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Course Grain Quality Module 6 Determining
the Chemical Characteristics of Milled
Rice Lesson 2 Why is amyclose content
important and how is it measured?
CLASSIFICATION RANGES
11
Course Grain Quality Module 6 Determining
the Chemical Characteristics of Milled Rice
Lesson 3 Why is gelatinization temperature
important and how is it measured?
Gelatinization temperature determines the amount
of time it takes for a particular variety of rice
to cook.

12
Course Grain Quality Module 6 Determining
the Chemical Characteristics of Milled
Rice Lesson 3 Why is gelatinization temperature
important and how is it measured?
13
Course Grain Quality Module 6 Determining
the Chemical Characteristics of Milled
Rice Lesson 4 Why is gel consistency important
and how it is measured?
Hard and soft gel consistencies
Gel consistency
If then
Gel consistency is hard, the cooked rice tends to be less sticky. Harder gel consistency is associated with harder cooked rices and this feature is particularly evident in high-amylose rice.
Gel consistency is soft, the cooked rice has a higher degree of tenderness. This is a preferred characteristic
Classification Length of gel (mm)
Hard 27-35
Medium Hard 36-40
Medium 41-60
Soft 61-100