1. Rapid Visco Analyser for Grain, Flour, Food & Feed

2. Outline What is an RVA? Hardware & advantages Software & advantages
What it measures
Sample presentation
Running a test
Applications
Conclusions

3. Variable mixing speed (shear)
What is an RVA?
Rotational viscometer that is able to continuously record the viscosity of a sample under conditions of controlled temperature and shear rate
Especially configured for testing the pasting properties of starch and starchy products
Programmable, multi-step test profiles
Variable temperature
Variable mixing speed (shear)

4. Hardware - RVA Sample can & paddle Drive motor & coupling Copper block
Hydraulics
Heating
Cooling
PCB

5. Hardware Advantages 1 Can and paddle Paddle blade “propeller” shape
Keeps starch granule suspension homogenous prior to gelatinization
Resists cavitation
Average shear rate known (20.1/rev, 53/s at 160 rpm)
Canister
Crushes in block giving good thermal transfer
Disposable or re-usable (x10)

6. Hardware Advantages 2 Searle vs Couette rotational viscometers
RVA is a Searle system, ie. inner paddle rotates
Fixed outer cup can be clamped to heating system
Allows rapid heating & cooling so fast tests
Allows precise temperature control so repeatable results
Searle
Couette

7. Hardware Advantages 3 Temperature control and measurement
PT-100 temperature sensors with
4 wire sensing
Accurate to 0.1°C, fast response
(+/- 14°C/min), reliable
Placed close to major shear point
where sample viscosity is measured,
ie. between outer paddle blade and cup
Profile temperature control
Precisely ramped temperature changes in test
Measuring block temperature vs sample temperature
Sample temperature ‘lags’ block temperature
Temperature gradient in sample when heating or cooling
Sensors in the sample only measure temperature at one point
Sensors in the sample disturb the flow (ie viscosity)

8. Hardware Advantages 4 Viscosity measurement: Speed control
Rapid proportional loop
Crystal locked, never needs calibrating
High precision gearless Maxon motors
Precious metal (RVA-TecMaster)
Linear torque to current
Low friction
Brushless (RVA 4500)
Very low friction
Low electrical noise
High precision 16 bit digitization

9. Software - TCW Real time graphing with overlay and QC limits option
Tabbed interface
Interactive display
Customizable, multistep methods and analyses with advanced options
Automation “short cuts”
Single page report with traceability data, results and graph
ER/ES compliant

10. Software - Advantages
Real time graphing, overlay and QC options for instant results during a test plus clarity.
Tabbed interface is familiar, easy to learn, intuitive to use.
Interactive display for clarity and ease of use.
Customizability and advanced options give flexibility for research and unique products and applications.
Automation “short cuts” are easy for routine operators, less experienced and infrequent users and students.
Single page report is convenient, complete, secure and includes traceability data.
ER/ES compliance ensures data security for food and drug safety audits. Log-on protects data and method profiles from accidental corruption or deletion. Auto generated backup file for safe storage.

11. What it measures Pastes of plant polymers and associated enzymes
Starch and starchy products eg. grains, flour
Food (thickener, binder, stabilizer)
Industrial (paper, adhesives, textiles)
Alpha-amylase (sprouting, malting, fungal)
Protein
Dairy, soy, gluten, gelatine
Protease, TG
Gum
Carrageenans, Xanthan, Pectin, Arabinoxylan
Xylanase

12. Starch Cooking in Excess Water
Gelatinization
Loss of crystalline order in starch lamellae
Pasting
Swelling, leaching of AM, polymer alignment
Retrogradation
Network formation
Amylose, amylopectin

13. Sample Presentation Sample & water in can 2 - 4 g sample 25 mL water
Paddle inserted into paddle coupling
Tower lowers assembly into split copper block
Copper block closes & paddle rotates
Sample viscosity measured & recorded continuously

14. Running a Test Prepare sample Insert can & paddle Press down tower
Copper block closes
Motor rotates paddle
Speed controlled
Temperature controlled
Sample viscosity measured
Data sent to PC
Test ends
Tower raises
Discard sample

15. Applications Food research groups, public and private Plant breeders
Starch manufacturers
Flour millers
Food ingredient manufacturers
Processed food manufacturers
Pet food and fish feed manufacturers
Grain traders 15

16. Applications – Whole Grain
Wheat
Durum
Rice
Corn
Barley
Oats 16

17. Wheat – Whole Grain 1 Stirring Number (SN) test
Viscosity after 3 minutes, 95oC test
Starch is rapidly cooked then digested by alpha-amylase enzyme produced during sprouting, if any
Small time window between gelatinization and denaturation
Wheat, barley, rye
High levels of damage give low viscosity, similar to FN method
ICC 161, AACC 22-08, Other
Stirring Number profile for testing sprout damage in cereals
0’0”
960 0’0”
160 0’10”
3’0”
3’0”
4.00g wholemeal, 25.0 mL water
Measure “Stirring Number” in RVU

18. Wheat – Whole Grain 2
Late maturity amylase, or “green amylase” associated with grain maturation
Does not require sprouting
Found in specific cultivars
SN & FN tests can fail to detect it
20 minute RVA pasting test detects it

19. Wheat – Durum Wheat, semolina, flour and pasta Pasta quality
Mainly depends on protein
Drying effects → RVA
High temperature drying
“Parboils” the pasta
Reduces cracking & cooking loss
Improves quality
RVA method
“Critical Paste”
Higher, earlier peak
Profiles for testing pasta quality (Whalen 2001)
0’0”
960 0’0”
160 0’10”
5’0”
15’0”
4.0g wheat & semolina, 5.75g pasta

20. Rice 1
Eating quality
“Setback” (Final – Peak) correlates to cooked rice texture
Detect effects of variety, aging, particle size, lipid binding
Breeders
Small samples, rapid tests
3.5g, 12.5 minute RVA pasting profile
AACC 61-02
Many ideotypes
Japonica, Indica, arboreo, fragrant, waxy
Short, medium, long; variable AM:AP24

21. Rice 2 Japanese method Prefer soft, cohesive rice Discerning market
Larger sample (3.5 g)
19 minute method for greater discrimination
Japanese rice pasting method 0’0”
960 0’0”
160 0’10”
1’0”
5’0”
12’0”
16’0”
19’0”

22. Rice 3 Pre-cooked rice Parboiled, “instant” Shorter cook time
Reduced cracking, higher proportion of whole grains
Rice grading
Visual assessment cannot detect low levels of pre-cooking
Cheating on head yield
RVA method readily detects pre- cooking by lowered peak & final viscosities
AACC method 61-02

23. Rice 4 Pasting temperature method
Rapid heating in RVA gives higher pasting temperature results than Amylograph or DSC
Method
Higher sample size (6 g)
Slower temperature ramp
AACC method (first approval)   
Pasting temperature method
0’0”
960 0’0”
160 0’10”
5’0”
20’0”
20’0”
6.00g ground white rice, 24.0g water
Measure PT

24. Corn Hard & Soft types Hydration rate & processing quality
RVA test more sensitive than density / flotation tests
High solids, slow temperature ramp
Masa, tortilla, corn chips
Profiles for corn hardness
a) Hard corn
0’0”
960 0’0”
160 0’10”
1’00”
20’0”
25’0”
28.0g aqueous slurry with 18% wholemeal dwb
b) Soft corn
2’0”
6’30”
11’00”
15’0”
17’30”

25. Barley 1 Storage of malting barley For making beer & spirits
>95% viability to malt
Storage life depends on sprout damage and storage conditions
Sprout damage measured by RVA SN method
Storage temp & grain moisture content
Model to estimate safe storage life used to manage grain storages

26. Barley 2 Malting Predict malting quality from barley
Profile for assessing barley and malt
0’0”
960 0’0”
160 0’10”
1’0”
4’12”
9’12”
14’12”
15’0”
Barley: 4.00g, Malt: 7.00g autolytic, 4.00g inhibited
Modify profile to max. temperature 69 oC for autolytic tests on malt.
Amylase activity can be inhibited using 0.1 mMol AgNO3/g malt or barley.
Malting
Predict malting quality from barley
Monitor green malt conversion
AgNO3 inhibition to track starch degradation during germination

27. Barley 3 Brewing Measure adjunct pasting temperature
Ensure it gelatinizes before heat deactivates amylase in the mash
Effect of added enzymes
Filtration issues due to residual starch, beta-glucan and protein
Process emulation
Process behavior
of a malt
Standard method
Mebak II 2.7 (STD1)

28. Oats Food applications Rolled oats & groats Health claims
Differs from other cereals
Starch is shear sensitive
High lipids, high beta-glucans
RVA method
20 min reduced shear test
Also AACC 76-22
Applications
Breeding
Process control (steaming, kilning, rolling)
Profile for assessing oats 0’0”
960 0’0”
115 0’10”
1’00”
4’0”
10’30”
15’0”
20’0”
3.63g ground oats (dwb)

29. Applications – Wheat Flour
Baking flour
Noodle flour
Malt amylase
Fungal amylase
Solvent Retention Capacity of soft wheat flour for cakes, cookies, biscuits, pastries 29

30. Wheat – Flour 1 Baking flours → pan breads Standard 1 test
More sensitive measure of amylase: peak & final viscosity
Detects heat treatment - peak
8x faster than Visco/Amylo/Graph
ICC 162, AACC etc.
Noodle flours
Silver nitrate to deactivate amylase
White salted
Higher peak associated with lower AM (null 4A) → good quality
Yellow alkaline
Profile for testing pan bread flour quality – STD1 profile
0’0”
960 0’0”
160 0’10”
1’0”
4’42”
7’12”
11’0”
13’0”
3.50g flour, 25.0 mL water

31. Wheat – Flour 2 Correlates with Visco/Amylo/Graph Pin and paddle types
Care
Amylograph or Viscograph
Torque cartridge (ie. need to define “BU” as cmg)
Correlations are product-dependent (different for eg. rice, corn etc.)

32. Wheat – Flour 3 Malt amylase
Small amount of amylase improves bread quality
3 minute SN test to optimise dosage
Fungal amylase
Anti-staling additive
Doesn’t persist through baking
20 min 50°C RVA test using a pregelled substrate
Dosage control

33. Wheat – Flour 4 Solvent retention capacity (SRC) for soft wheat flours
Four solvents:
Water
50% sucrose: pentosans, gliadin
5% sodium carbonate: damaged starch (high pH to solubilize it)
5% lactic acid: partially solubilises the gluten proteins
Biscuits, cakes, cookies, pastries
10 minute, 25 to 50°C test
Correlates to Extensograph

34. Applications – Food Native starch ingredients
Modified starch ingredients
Hydrocolloid ingredients
Soup
Salad dressings
Corn flakes
Yoghurt
Processed cheese 34

35. Native Starches STD1 most commonly used Cereal
Higher pasting temp re lipids
Strong setback due to amylose
Root & tuber
Higher peaks, lower PT
Inhibited setback – phosphorylation in potatoes
Waxy
Lower PT, no lipid binding
Low setback, no amylose network
High Amylose
Require temp > 100°C to paste

36. Modified Starch Example: crosslinking & substitution
RVA-S4 PRESENTATION
Modified Starch
Example: crosslinking & substitution
Uses: thickeners, stabilizers and clarifiers in soups, puddings, pie filings and retorted foods
Extended time at high heat and moderate shear
Reveal stability related to batch cooking processes

37. Dextrins and Instant Starches
Highly depolymerized
Low viscosity, soluble, DE
sweetness, yellow – white
Adhesive pastes, sweeteners,
binders, batters
Instant Starches
Low temp or cold-swelling
Pregelatinized or highly substituted
Sauces, soups, microwaved products, bakery, beverages
RVA method shows cold solubility, residual hot-swelling starch, and cooking stability

38. Carrageenan 1 Structure Alt. -1,3 & -1,4 galactopyranose
Three types: kappa, iota, lambda (see below)
Properties
Ionic – gelling promoted by cations eg. in milk
-carrageenan forms strong, thermoreversible, brittle gels; syneresis prone. -carrageenan forms weaker gels. -carrageenen does not form a gel. Also hybrid  & .
Applications
Thickened and gelled dairy products

39. Carrageenan 2 Rheology Fundamental rheometers often used
RVA: simpler, faster method
RVA method
“diagnostic” for determining type of gum(s) in product
Cooling ramp (80 – 20°C) to reveal gelling behaviour
Gum at 0.2%, starch 1.5%, milk; gum pre-hydrated

40. Xanthan, locust bean and guar 1
Structure
Xanthan: -1,4 glucopyranose,
C3 trisaccharide residues
LBG, guar: -1,4 mannose spine,
-1,4 galactose residues
Properties
Xanthan: High pH stability, heat/salt/acid induce ordering, shear-thinning, thixotropic, syneresis-resistant
LBG: Hot soluble (>85°C), very weak gels G:M 1:4
Guar: Cold soluble, pH stable, does not gel, G:M 1:2
Applications
General food thickeners, texturizers and gelling agents
Synergistic gelling between Xanthan & LBG and guar

41. Xanthan, locust bean and guar 2
RVA method 1
Cooling ramp (80 – 20°C) to reveal gelling behavior
Gum at 1%
Weak gel forming of individual gums on cooling
Synergistic gelling of xanthan and LBG

42. Xanthan, locust bean and guar 3
RVA method 2
High and low shear during temperature ramp
Designed to detect point of gum solubilization
Can be performed at different ionic and pH conditions
Guar
Xanthan

43. Pectin 1
Structure
-1,4 D-galacturonic acid (“smooth” regions) with acid & methyl ester groups (high or low sub), and 1,2-  - rhamnopyranose units with galactose & arabinose side chains (“hairy” regions). Can be modified with amides.
Properties
HE sub: Gelling requires low pH and >55% sugar
LE sub: Ionic, gels with Ca2+
Applications
Confectionary, jams

44. Pectin 2
RVA method
Cooling ramp (80 – 20°C) to reveal gelling behavior
Curves similar but high ester >10x higher viscosity
High ester
Low ester

45. Konjac Structure Copolymer -1,4 D-mannose with D-glucose residues
Properties
Viscous, shear thinning solutions, strong gelling at high pH
Forms thermoreversible gels with xanthan
Applications
Beverages
RVA method
Cooling ramp (80 – 20°C) to reveal gelling behavior
Sudden gelling on cooling
Breakdown on shear

46. Hydration of Hydrocolloids
RVA-S4 PRESENTATION
Hydration of Hydrocolloids
Sandra Hill and Nuno Sereno, Division of Food Sciences, University of Nottingham, UK

47. Powdered Soup Mix Cream of Chicken, Chicken Noodle, Hearty Beef,
RVA-S4 PRESENTATION
Powdered Soup Mix
Cream of Chicken, Chicken Noodle, Hearty Beef,
French Onion, Tomato,
Vegetable

48. RVA-S4 PRESENTATION
Salad Dressings

49. Cornflakes Reverse engineering Original cornflakes
Batch cook and flake process, slow and costly
Low cold viscosity – good bowl life
“Copy” product
High shear process, ie. extrusion
Cold swelling – poor bowl life
Could be fixed eg. add surfactant!

50. Yoghurt Description Semi-gelled milk fermentation product
Integrate incubation and test in RVA – “mini pilot plant”
RVA
Multiple temperature and shear profile to sterilize etc.
Effects of season, processing, aging, formulation
SMP heat treatment
low
medium
high

51. Processed Cheese Description
Emulsifying salts used to hydrate protein complex, sequestering calcium that previously stabilized the casein
Rate of hydration important for processing
Mini pilot plant
RVA
7 minute, 80°C
High shear to
emulsify
Modified paddle

52. Applications – Feed
Dog food
Cat food
Aquatic feed 52

53. Application Example 2 Dry dog food Starch binds pellets,
Controls texture
Omnivores
Some starch in diet
Brand and batch effects
Similar general curve shape, one obviously low viscosity sample

54. Application Example 3 Dry cat food Obligate carnivores
Raw or retrograded starch can make cats sick
Starch must be fully cooked
Aged food
Loss of cold viscosity
Retrogradation of starch

55. Application Example 4 Fish food Salmon, high fat Starch <10%
Controls binding, durability
Controls density – float/sink rate
RVA test
12 g sample
Ethanol dispersal
Feeds
Large range in viscosities!
Green curve undercooked
Poor cohesion
Dead fish

56. Conclusions Innovative and state-of-the-art hardware and software
Providing many advantages
Easy to use
Fast tests
Small sample size
Precise and repeatable results
Flexible test routines
Traceable
Robust
Applications in software, RVA Handbook and library of publications