What is Falling Number?
The determination of alpha amylase activity by the Falling Number test method is attributed to the gelatinization of starch.
The test consists of the thermally induced gelatinization of starch in a mixture of wheat flour and water, resulting in a viscous fluid. A plunger is allowed to fall through the fluid, and the time recorded for the plunger to reach a certain level is measured.
The value for the Falling Number test is expressed in minutes.
The higher the Falling Number, the lower is the alpha amylase activity. Conversely, lower Falling Number values indicate higher alpha amylase activities.
Factors such as an elevated level of sprouted grain, pre-harvest sprouting, among others, can increase the alpha amylase activity in wheat. Subsequently, flours from the wheat with increased alpha amylase activities can adversely affect the baking performance of the flour.
Other factors such as protein content of the wheat, ash content of the flour, test weight of the wheat, moisture content of the grain, and the quality of gluten can also affect the baking performance of the wheat.
Why Is Falling Number Important In Wheat?
In the processing of wheat, the starch component is reduced to smaller substances.
In the baking process, starch components of wheat flour are gelatinized. The breakdown of starch components in flour is not always undesirable. However, high levels of enzyme activities can adversely affect baking performance of a flour.
Some of the potential problems associated with very low alpha-amylase activity in wheat include:
- Sticky dough
- Inability to work dough
- Poor risings
- Gummy texture
- Poor volume
- Poor slicing
- Misshapen loaves
- Baking variances
- Difficulty in commercial baking
To minimize the risk of these conditions, flour mills and wheat purchasers establish minimum Falling Number levels.
It is understood that:
The objective is to meet, not exceed, the Falling Number Level required for a product.
Knowing the reason a Falling Number declines is important in establishing strategies for managing and controlling Falling Number levels.
The most important factor is pre-harvest sprouting.
Pre-harvest conditions cause the wheat to begin the germination process. Increased enzyme activity and, especially, alpha-amylase activity reduces the Falling Number.
Other factors which contribute to a low Falling Number include:
- Rain in the growing wheat
- Harvest delays
- Moist conditions during the growing season
- High humidity
- Repeated ner cycle
- Damaged or lodged wheat
- Poor or excess moisture after harvest
- Poor grain storage
- High grain moisture
- Poor temperature control
Mixing sound wheat with low Falling Number wheat
Not all sprouted wheat will show a low Falling Number. Some wheat may show significant levels of enzymatic activity without visible sprouting.
Laboratory tests will determine the Falling Number of wheat.
Maintaining an acceptable Falling Number prior to harvest is a result of strategies implemented well in advance of the harvest period.
Once significant levels of pre-harvest sprouting have occurred, there are very few, if any, effective strategies that can be employed post-harvest that will return the grain to its original condition and quality.
Therefore, of greatest importance is the development and implementation of strategies to prevent the occurrence of sprouting rather than attempting to remedy the situation post-harvest.
Choice of Winter Wheat Variety
The variability of individual varieties to pre-harvest sprouting is genetically determined and therefore varies between wheat varieties.
When choosing a winter wheat variety, a number of agronomic factors need to be considered, including, but not limited to:
- Sprouting protection
- Dormancy
- Adaptation to the local climate
- Maturity
- Expected harvest conditions
- Resistance to biotic and abiotic stresses
- Grain quality and other market requirements
A wheat variety that may be well adapted to dry harvesting conditions may not be as well adapted to a region where wheat is mature and harvested while still green due to the presence of effective rainfall.
Therefore, the situation of local conditions, the preferences of wheat purchasers and other market constraints should be considered when selecting a winter wheat variety.
Careful Assessment of Crop Maturity
Prior to the onset of unsafe harvest conditions, the Falling Number of the grain should be protected.
If the grain is allowed to remain in the field after it has fully matured, particularly if it is partially damaged, it is at increased risk of pre-harvest sprouting.
Prior to the onset of unsafe harvest conditions, the grain should be assessed for maturity, moisture content, and other quality factors.
Exposure to moisture causes wheat grain to begin germination and activate enzymes. This can occur at the later stages of grain development. If conditions remain favorable, the alpha-amylase enzyme becomes even more active.
Not all wheat exposed to rain will have a low Falling Number. Other factors will determine the risk, including:
- How long the grain is kept wet
- Air and grain temperatures
- How mature the grain is
- The wheat variety
- How dormant the wheat is
- Conditions of the grain prior to harvest
- How many times it rains
- How long grain is kept wet prior to being harvested
How long grain is kept moist, and the conditions of the grain prior to being harvested determines the level of risk for harvesting wheat at a less-than-optimal stage of development. The factors listed previously must be taken into account along with local conditions to determine the ideal time to harvest wheat.
Delaying harvest to avoid drying costs can increase the risk of losing good grain quality. This is particularly true if the weather turns and rain comes.
There are many factors to take into account regarding quality and cost when determining the ideal time to harvest wheat.
Before each harvest, adjust the following:
- Cylinder/Rotor Settings
- Concave Clearance
- Fan Speeds
- Sieve Settings
- Harvest Speed
- Grain Handling Equipment
The goal is to harvest sound, fully-mature grain and minimize mechanical injury.
Evaluate Grain Quality after Harvest
Early testing of grain samples is a relatively recent development that has benefited grain-quality management.
Do not assess the quality of wheat you have stored for many months by testing it for the first time when it is removed from storage.
Prior to long-term storage, samples of wheat should be evaluated for:
- Moisture
- Test Weight
- Falling Number
- Protein
- Percent Foreign Matter
- Damaged Kernels
- Other Quality Characteristics
If Falling Number tests indicate that wheat is deficient in amylases, the wheat should be separated from other lots, as low levels of amylases can adversely impact the quality of other wheat lots during storage and transport.
Grain Drying
Wheat should be dried to prevent deterioration and to safely store the grain.
The purpose of grain drying is to remove moisture to a level that would preclude further deterioration of grain and allow safe storage of the grain.
Drying should be controlled to avoid adverse effects on the quality of wheat and to minimize consumption of energy.
Prior to using a drying system, understand the grain to be dried, the drying system, the local climate, storage practices, and the purpose for which the grain will be utilized.
The general objective of drying grain is to:
Uniformly reduce the moisture content of the grain to a safe level for storage.
Maintain Proper Grain Storage Conditions
After drying, proper storage conditions are vital.
Grain must be stored in a way that prevents
- Moisture build up
- Condensation
- Mold
- Rusted grain
- Insects
- Further deterioration
Storage conditions must be properly managed and frequently monitored.
Grain Temperature Matters
Temperature is important because it affects the rates of deterioration of grain and the activity of insects and microorganisms.
Prior to drying, uneven grain moisture can cause condensation and favoren microbial activity.
Monitoring grain temperatures can help identify problems.
Grain may not always be “safe.” If temperatures begin increasing, further investigation is warranted.
Aeration and Falling Number Management
Temperature and moisture of stored grain can be improved with aeration.
Aeration:
- Allows for more even temperatures in the grain
- Decreases the risk of condensation
- Allows for more even moisture content
- Allows for more even quality
- Aeration is appropriate for the condition of the grain as well as the conditions of the surrounding environment.
- Just turning the fans on is not adequate.
- Conditioning the grain is better than moving air through the grain unnecessarily.
There is a natural tendency for moister air to rise and for drier air to sink. This can promote the migration of moisture throughout stored grain. Grain masses that are not uniform in temperature are more at risk for molding, heating, and insect infestation. For these reasons it is a good practice to monitor the temperature of stored grain, especially if the surrounding environment is changing.
Falling Number is negatively affected by mixing different lots of grain. Wheat Lots should be kept separate to best assure that the customer specifications for Falling Number are met. Maintaining the identity of individual lots will allow for more options during the blending of grain to produce flour.
Blending flour from lots of different Falling Numbers can allow a mill to produce a flour suitable for various end uses.
It should be clear that achieving a particular Falling Number value is not the goal of blending.
Flour from those blends needs to be tested for:
- Protein level
- Gluten strength
- Dough behavior
- Baking performance
Achieving a specific Falling Number value does not ensure optimal flour for baking.
How Millers Can Maintain Better Falling Number
The consistency of the final flour depends on the mill management and control.
Well-managed mills have proper wheat conditioning before processing. This usually includes:
- Cleaning – Removal of foreign materials
- Moisture conditioning – Setting the wheat for optimum milling and Bran/Endosperm separation
- Blending of wheat lots of similar quality
- Flour quality should be monitored continuously.
- Testing finished flour should be part of the quality control process.
The importance of trend analysis should be emphasized. For example, falling flour quality over a series of production runs should be thoroughly researched. Possible reasons may include variations in the raw materials used, milling conditions, laboratory analysis, and/or customer specification.
What Is a “Good” Falling Number?
Factors affecting the appropriate Falling Number:
- Variety of wheat
- Country of origin
Wheat is often combined across fields in storage and uneven sprouting occurs. Later, when the wheat is processed, the negative impacts of sprouting cannot be reversed, and Falling Number cannot be improved. Drying and storing wheat can help avoid problems associated with high alpha-amylase activity.
- Wheat grade
- Wheat flour type
- Type of bread
- End product
- Customer requirements
Wheat is milled to produce different flours for various uses. Bread made using a particular flour may require a different Falling Number compared to other flours.
Why the Ideal Falling Number is Often Misunderstood?
Falling Number measures the activity of alpha-amylase. High Falling Number does not always imply high quality of wheat.
Some wheats with high or acceptable Falling Number may have issues related to:
- Protein and gluten
- Damage to kernels
- Dough
- Milling
Several factors can negatively affect the quality of wheat. Falling Number is one of the many metrics used to assess the quality of wheat.
Falling Number Problems During Wet Harvest
With wet weather expected during harvest, there are more opportunities for problems to arise.
To lessen the chance of problems occurring, a grower should:
-Before harvest
- Check the weather
- Check maturity of the crop
- Determine the capacity of the harvest equipment
- Be prepared to use drying equipment
- Prepare grain storage
- Make arrangements for a lab test
- Decide on the best storage location
-During harvest
- Harvest only the most mature wheat
- Minimize damage to the grain
- Keep the grain lots as separate as possible
- Measure the moisture of the grain
- Sample the grain
-After harvest
- Have the falling number test done on the sample
- Dry the grain to a safe storage moisture
- Cool the grain
-While the grain is stored
- Keep the storage temperature as low as possible
- Keep storage moisture as low as possible
- Inspect the grain for storage pests
- Maintain an aeration fan
- Keep a record of the grain
This will help minimize the risk of falling number problems.
Representative Sampling
Because of the nature of laboratory testing, sampling plays a critical role in determining the end result.
An inadequate sample can result in an incorrect test result.
Because of differences in growing conditions, wheat from different fields can vary and samples from the same field can vary because of differences in maturity.
- Sampling should achieve:
- Representation of the complete lot
- Homogenization of the sample
- Reduction of sample size
- Proper identification
- Protection from loss or gain of moisture
- Testing using a standard or accepted method
Lab personnel should use the instruments in a manner described in the standard.
Falling Number Management
Common Shortcomings
There are several shortcomings in the management of Falling Number during the processing of wheat. These shortcomings are as follows:
Shortcoming 1: Excessive Delay in Harvest
Grain can begin sprouting due to high moisture from rains.
Shortcoming 2: Reliance on Grain Drying
Grain drying will not reverse the effect of amylase on the starch.
Shortcoming 3: Inadequate Quality Control
Tests should be conducted on each wheat lot prior to their being mixed.
Shortcoming 4: Testing Occurs Only at the End
Tests should be conducted at intervals during storage.
Shortcoming 5: Failure to Regulate Storage Temperature
Uneven temperatures during storage can lead to spoilage.
Shortcoming 6: Single Test Focus
Falling Number test offers very little information about the end-use quality of the wheat.
Shortcoming 7: Expecting Unrealistic Targets
The target should be a specified quality, not the absolute maximum.
Action Plan
During harvest
- Keep equipment functional and readily available.
- Store grain in a dry condition.
- At harvest
- Don’t harvest too early or too late.
- Harvest to minimize kernel damage.
- Measure moisture of each lot harvested.
- Keep lots identified.
- Sample to represent the entire lot.
After harvest
- Test Falling Number if needed.
- Remove moisture if grain is too wet.
- Lower the temperature of grain to be stored.
- Separate grain lots if storage space allows.
- Document quality.
- While in storage
- Watch for pests.
- Check for condensation.
- Maintain desired temperature.
- Adjust for desired moisture.
If a certain temperature is maintained over a long period of time, locate the cause quickly.
- Prior to milling
- Review Falling Number.
- Review protein content.
- Review other quality characteristics.
If needed, create a wheat blending plan to manage quality.
Can the Falling Number be increased post-harvest?
There is no reliable way to repair the changes post-harvest. Sprout control and protection of the grain from further moisture would prevent further decline. Controlled wheat blending may satisfy a customer requirement for a given specification.
Is lowering the moisture content of the grain likely to lower the alpha-amylase activity?
Drying grain reduces the moisture content of the grain and protects the grain from further deterioration. It does not change the alpha-amylase activity of the grain.
Will sprouting change the Falling Number?
Yes, in most cases, sprouting increases the level of alpha-amylase and decreases Falling Number.
Is it better for Falling Number to be high?
Falling Number needs to be within product specifications to meet customer expectations based on the end use of the product.
Can wheat with low Falling Number be used?
It depends on the level and the purpose for which the wheat will be used.
How should it be handled?
Wheat should be quickly dried to decrease the moisture content to an acceptable level, and stored at a low temperature. Wheat should be kept separate from other wheat of higher quality.
Can it be adjusted to meet specifications?
Blending can adjust the level of a flour to meet specifications, but flour should be tested to ensure that it meets specifications and other qualities are within acceptable limits.