Corn and oat processingtechnologiesProf. Dr. Nathan Levien Vanier

Grain Processing TechnologiesClass 12 – October 19th, 2017

Corn production

Source: FAO (2017)

Corn utilization

Corn processing

Freshly harvested corn

Cleaning, drying and storage processes

Dry milling Wet milling Nixtamalization

Flaking gritsBrewing gritsOther gritsFlourGermBran

StarchGermBranSoaking water

Nixtamalized flourTortillaChips

Product classification according to particlediameter

Source: Eckhoff, Dry Milling, In: Encyclopedia of Grain Sci., 2004.

Milling quality depends on maize/cornstructural characteristics

Corn endosperm

Source: Delcour and Hoseney, Principles of Cereal Science, Chapter 1, 2010, 260p.

Corn endosperm characteristics

Dry milling

Corn

Cleaning and selection

Milling

Whole maize flour

Selection and sieving

Dry milling

Dry milling

Corn grains

Cleaning and selection

Degermination

Milling

Flour from degerminated maize/corn

GermPericarp

Oil extraction

Selection and sievingStarch/GlucoseAlcohol

Conditioning (21% moisture)

Selection

Milling

Conditioning step details

Conditioning step details

Addition of 6% to 8% of water in relation to grain mass Tempering for 10 to 40 min.

Corn degerminator

Milling yield of 9 hybrids using a Beall-typedegerminator

Source: Eckhoff, Dry Milling, In: Encyclopedia of Grain Sci., 2004.

Fonte: Deepa & Hebbar et al., Journal of Cereal Science, v. 60, p. 569-575, 2014.

(a) control; (b) infrared at 159 °C/173 s/40%; and (c) infrared at 166 °C/164 s/40%.

Micronization treatment of corn flour withinfrared at different time-temperature conditions

Fonte: Deepa & Hebbar et al., Journal of Cereal Science, v. 60, p. 569-575, 2014.

Micronization treatment of corn flour withinfrared at different time-temperature conditions

Increased conservability

Wet milling

1) Soaking

Bins with water recirculation set at 52ºC.

Time varies from 20 to 48 h.

Wet milling

1) Soaking

2) Germ removal

Mechanical shearing and cutting.

Wet milling

1) Soaking

2) Germ removal

Mechanical shearing and cutting.

Wet milling

1) Soaking

2) Germ removal

Mechanical shearing and cutting.

Separation using hydrocyclone.

Wet milling

1) Soaking

2) Germ removal

3) Fiber separation

Wet milling

1) Soaking

2) Germ removal

3) Fiber separation

Wet milling

1) Soaking

2) Germ removal

3) Fiber separation

4) Protein separation

Wet milling

1) Soaking

2) Germ removal

3) Fiber separation

4) Protein separation Separation by density profile using a disc centrifuge.

Wet milling

1) Soaking

2) Germ removal

3) Fiber separation

4) Protein separation

5) Starch

Wet milling

1) Soaking

2) Germ removal

3) Fiber separation

4) Protein separation

5) Starch

Separation using hydrocyclone.

Nixtamalization

Maize + Ca(OH)2Cooking for 25-30 min + hydrationfor X time

Drainage of solution

Germ removal

Milling

Nixtamalized massa

Drying

Sieving

Nixtamalized maizeflour

Cooking

Table Tortillas

Frying

Chips

Mexico - 1836

Nixtamalized maize after water drainage

Nixtamalization

Fonte: Cornejo-Villegas et al., LWT, v. 53, p. 81-87, 2013.

Calcium content in maize fractions and nixtamalized flour.

Nixtamalization – research results

149 μm

420 μm

Nixtamalization – research results

Fonte: Palacios-Fonseca et al., Journal of Food Engineering, v. 93, p. 45-51, 2009.

Nixtamalization – research results

Fonte: Palacios-Fonseca et al., Journal of Food Engineering, v. 93, p. 45-51, 2009.

Corn flakes

Oat processing

Oat grains

Cleaning and selection

Dehusking

Stabilization (toasting)

Flakes production Cutting

Flakes production

Partial milling

Fonte: Ganbmann e Vorwerck, In: The oat crop, Ed. Chapman & Hall, 1995.

Cleaning and selection

Oat processing

Oat grains

Cleaning and selection

Dehusking

Stabilization (toasting)

Flakes production Cutting

Flakes production

Partial milling

Dehusking – Rotary impact mill

Fonte: Ganbmann e Vorwerck, In: The oat crop, Ed. Chapman & Hall, 1995.

Greater hulling degrees are obtained atlow moisture levels

Fonte: Ganbmann e Vorwerck, In: The oat crop, Ed. Chapman & Hall, 1995.

Hulling degree as a function of peripheralspeed of a Rotary impact mill

Oat processing

Oat grains

Cleaning and selection

Dehusking

Stabilization (toasting)

Flakes production Cutting

Flakes production

Partial milling

83-100 ºC for ±30 min

Stabilization

Moisture level may be increased for successfull stabilization of oats

Fonte: Ganbmann e Vorwerck, In: The oat crop, Ed. Chapman & Hall, 1995.

Oat processing

Oat grains

Cleaning and selection

Dehusking

Stabilization (toasting)

Flakes production Cutting

Flakes production

Partial milling

Cutting is performed in a drum with knivesattaches

Fonte: Ganbmann e Vorwerck, In: The oat crop, Ed. Chapman & Hall, 1995.

Oat processing

Oat grains

Cleaning and selection

Dehusking

Stabilization (toasting)

Flakes production Cutting

Flakes production

Partial milling

Flakes production

94-100 ºC for ±30 min

Fonte: Gates et al., Journal of Cereal Science, v. 48, p. 288-293, 2008.

Effects of tempering time and temperatureon flake thickness