Dairy processing: Vitamin addition

On this page

• Introduction
• Definitions
• Raw materials
• Preparation of vitamin solutions
• Vitamin addition
  • Continuous flow method – fluid products
  • Batch method – fluid products
  • Continuous flow method - dry powdered premix added to finished powder
  • Batch method - dry powdered premix added to finished powder
• Finished product evaluation - quality control
• Calculations
  • Theoretical values
  • Calculated values
  • Converting International Units (IU) of Vitamin D to micrograms (µg)

Introduction

The following provides recommended practices that dairy processors can use to ensure the accurate addition of vitamins to fluid, evaporated and dry milk products.

Definitions

For the purpose of this document, the following definitions apply:

Vitamin premix

A vitamin preparation supplied to a commercial processor, to be used in the fortification of fluid milk, milk powder and evaporated milk products as supplied or as a part of a vitamin solution. Vitamin premixes are available as liquid concentrates, powders or beads.

Vitamin solution

A blend of a vitamin premix and a suitable diluent.

Raw materials

• Have written specifications for vitamin premixes (includes liquid concentrates, powders and bead) which specify the supplier, potency, form and stability
• Ensure that the vitamin premix meets the written specifications such as a certificate of analysis from the supplier and through testing
  • if the vitamin premixes to be added to a finished milk powder are a combination of vitamin A and D in a milk powder carrier, ensure that the carrier powder does not contaminate the finished product (for example, have a supplier guarantee or micro analysis for standard plate count (SPC)/aerobic colony count (AAC), coliforms, Salmonella)
• Store vitamin premixes according to the manufacturer's specifications. Once opened, use these premixes before the expiry date to prevent loss of potency.
  • Vitamin D is light sensitive and therefore loses potency if stored in clear containers exposed to light

Preparation of vitamin solutions

• Aim for finished product vitamin levels that meet the claim made on the Nutrition Facts Table (NFT) which also meet the regulatory requirements
  • allow for seasonal variations and processing variables, for example, rework which may contain previously added vitamins, or the shelf-life of the finished product
• Post written instructions for preparing vitamin solutions in the preparation area
• In order to assure measurement accuracy, use appropriate measuring devices (graduated cylinders or syringes) of sufficient sensitivity for the dilution being performed
  • for example, a 1000 mL graduated cylinder would not be appropriate to measure 10 mL of vitamin premix
• Prepare dry vitamin mixes according to the supplier's direction and maintain them in solution throughout the production
  • constant agitation, such as with a magnetic stir bar and plate, may be required to prevent settling
• Prepare vitamin solutions just prior to use and, when not in use, store them in such a manner  to minimize loss of vitamin potency, preferably in insulated vessels at 4°C
  • keep storage time to a minimum, no longer than 24 hours
  • discard left-over solution at the end of the day
• Identify containers of vitamin premix and vitamin solutions with their contents and use
  • clean and sanitize containers and equipment used for dilution daily, or more frequently as necessary

Vitamin addition

Vitamin addition can be accomplished at different points in the processing system through continuous flow or batch methods.

Continuous flow method - fluid products

• Avoid changing pump settings by preparing vitamin solutions in concentrations that will allow the use of a single feed rate for all products
  • if the pump is of a variable speed type, either lock the setting, or check and record regularly that no unauthorized adjustments have been made
  • a change in the pump speed (flow rate) alters the calculations for the amount of vitamin required and would result in an inaccurate amount of vitamin being added
• Use a positive displacement type pump otherwise negative pressures at the point of injection can create problems
  • a small vacuum can result in relatively large volumes of vitamin concentrates being drawn into a milk system in a very short time period
• Prepare a suitable excess of vitamin solution to prevent the possibility of running out of solution before the end of the production run
  • the amount of vitamin solution not used should be measured, recorded and taken into consideration in calculating the levels of enrichment
    • in most cases a 10% excess is suitable
• Add vitamin solutions that contain fat soluble vitamins after the separation step otherwise any fat soluble vitamins would be removed with the fat
• Add the vitamin solution before pasteurization
  • the vitamin solutions are not sterile, therefore need to be added prior to pasteurization
  • the best point of injection is ahead of the homogenizer, which in most cases is the point of low pressure which allows the homogenization process to distribute vitamin(s) throughout the milk
• Install the vitamin pump:
  • the injector site should be located at a point in the production line where minimal pressure fluctuation occurs
  • use a line (food-grade tubing), from the pump to the processing line, of minimal length and of transparent material, so that flow bubbles or anything which might prevent the flow of vitamins into the product can be observed
  • ensure the pump operates only when the pasteurizer is in forward flow and does not function when the system is in divert mode
    • inter-wire the pump and the diversion device so that when the pasteurizer switches to divert the solution pump shuts off, and when the pasteurizer switches back into forward flow the solution pump comes on again
• Keep the vitamin pump and pipelines clean and in good condition. Keep sanitation and maintenance records for the equipment.
• Check the vitamin delivery system at start up and after changeovers for leaks, air locks and correct feed rate setting. Keep records of these checks and any corrective actions taken.
• Check and record the level of vitamin solution in the vitamin solution reservoir at least hourly to ensure the amount of vitamin solution is being used at a consistent rate and will not run out before the end of production run
  • record any further addition of vitamin solution to the reservoir
  • note any problems such as leaks or air locks on the record with the time and the action taken to resolve it
• Have a written contingency plan which can be implemented in the event that the vitamin pump or other parts of the vitamin delivery system fail
  • do not continue production without effective vitamin fortification

Batch method – fluid products

• Add vitamins after separation, but before pasteurization, for the aforementioned reasons
• Accurately measure the volume of milk to be fortified and the vitamins to be added
• Agitate the milk sufficiently to ensure homogeneity after the addition of the vitamin solution

Continuous flow method - dry powdered premix added to finished powder

• Calibrate the volumetric feeder to consistently deliver the desired amount of vitamin premix prior to start up
  • lock the setting or check and record regularly that unauthorized adjustments have not been made
  • a change in the flow rate alters the calculations for the amount of vitamin required and would result in an inaccurate amount of vitamin being added
• Record the amount of vitamin premix added to the hopper at start up and during production. Product left in the hopper at the end of production should be weighed out.
  • the difference in these values can be used to determine the calculated value
• Check the level of vitamin premix in the hopper on a regular basis (hourly) to ensure the hopper does not run out of vitamin premix, or install a low level alarm
  • keep a record of these checks
  • note unusual occurrences on the record and the corrective actions taken
• Add vitamin premixes prior to final sifting
  • adding vitamins to milk powders before drying destroys the vitamins
  • a mix step ensures homogeneity
• Ensure that the volumetric feeder operates only when the system is in forward flow
• Have a written contingency plan which can be implemented in the event that the vitamin delivery system fails
  • do not continue production without effective vitamin fortification

Batch method - dry powdered premix added to finished powder

• Calculate and record the amount of vitamin premix added to the blender containing a premeasured amount of milk powder
• Accurately measure the amount of milk powder to be fortified and the vitamins to be added
• Agitate the milk powder sufficiently to ensure homogeneity after the addition of vitamin premix

Finished product evaluation - quality control

In order to verify the quantity of vitamin(s) in the finished product, maintain records and perform laboratory analysis as outlined below.

Records

• For each lot of product produced, keep records of:
  • name of product, production code and/or product best before date
  • the total amount of vitamin solution prepared
  • the amount of vitamin solution used
  • the amount of product produced
  • the calculated amount of vitamin in the product based on the vitamin solution consumption (see Calculations for examples)
  • the amount of rework and fresh milk used
    • rework has added vitamins whereas the fresh will require fortification

Analysis

• Routinely sample and analyze all enriched products
  • verification of vitamin analysis should be conducted at a frequency that ensures regulatory requirements are consistently met
  • do this more frequently if deviations are encountered
  • taking 3 samples is recommended
    • 1 from the beginning, middle and end of the production run
  • inexpensive vitamin should be done monthly
  • expensive vitamin should be done every 6 months
  • use an accredited laboratory for the vitamin analysis

Review

• Compare calculated values and theoretical values on a daily basis to ensure correlation (see examples in Calculations)
  • investigate significant differences and document any corrective action
• Compare the calculated values with the lab analysis
  • a considerable range can be expected between these 2 values due to several factors (for example, sample storage temperature, method differences and errors)
  • look for trends between the 2 values rather than equivalent values

Calculations

The Food and Drug Regulations (FDR) outlines the vitamin fortification of dairy products based on the recommended daily intake (RDI) as per Schedule K.  Table 1 illustrates an example of the vitamin fortification levels based on 100 millilitres (mL) of fluid milk, reconstituted dry milk, or  reconstituted evaporated milk.

Determining the volume of a vitamin premix prepared by weighing

Liquid premixes can be measured by weight instead of volume. Use the specific gravity (density) of the liquid premix to convert this weight to a volume.

Use the formula V = M / SG

where

V = amount of liquid vitamin premix used (mL)
M = weight of liquid premix used (g)
SG = specific gravity (density) of liquid premix (g/mL)

Example calculation

The specific gravity of a liquid vitamin premix is 1.045 g/mL. A weight of 3.5 g was used.

What is the volume of the liquid vitamin premix used?

V = M / SG
V = 3.5 g / 1.045 g/mL
V = 3.35 mL of liquid vitamin premix used

Determining the concentration of a diluted vitamin solution

If a liquid vitamin premix is further diluted prior to use, determine the concentration of the diluted vitamin solution prior to calculating either the theoretical value or the calculated value.

Use the formula  C_d = (C_p × V_p) / V_d

where

C_p = concentration of the vitamin premix (IU/mL)
V_p =  volume of the vitamin premix used  (mL)
V_d =  volume of the diluted vitamin solution to be prepared (mL)
C_d =  concentration of diluted vitamin solution (IU/mL)

Example calculation

The concentration of a vitamin D premix is 205,000 IU/mL. 24 mL of this premix is used in the preparation of 500 mL of diluted vitamin solution.

What is the concentration of the diluted vitamin solution?

C_d = (C_p × V_p) / V_d
C_d = (205,000 IU/mL × 24 mL) / 500 mL
C_d = 9840 IU/mL

This value (C_d) will be used for "C" when calculating the theoretical value or the calculated value in the next 2 sections.

Theoretical values

Theoretical value is used to determine how much vitamin premix should be added to achieve the desired vitamin concentration in the final product. The pasteurization method used (batch or continuous flow) will affect how this value is calculated, as will the use of a diluted vitamin premix.
Note: for the purpose of the calculations, the quantity of milk to be fortified must be converted to mL before entering it into the formula.

Batch method

V = TQ / C

where

V = volume of vitamin premix used (mL)
T = theoretical concentration of vitamin in the final product (IU/mL)
Q = quantity of milk to be fortified (mL)
C = concentration of vitamin premix (IU/mL)

Example calculation

If the desired theoretical concentration (T) in the final product is 38.15 IU/100 mL of Vitamin D (refer to Table 1), calculate the volume of vitamin premix (V) required in order to achieve this desired fortification level.

First, convert the theoretical concentration of vitamin to IU/mL:

38.15 IU/100 mL / 100 mL = 0.3815 IU/mL

V = volume of vitamin premix used (mL)
T = 0.3815 IU/mL of Vitamin D
Q = 1800 L (1800 L × 1000 ml/L = 1,800,000 mL)
C = 205,000 IU/mL of Vitamin D

V = TQ / C
V = [0.3815 IU/mL x 1,800,000 mL] / 205,000 IU/mL
V = 686,700 IU / 205,000 IU/mL
V = 3.349 mL

Therefore, the volume of vitamin premix needed to achieve a level of 38.15 IU/100 mL of Vitamin D in the final product is 3.35 mL. 

Continuous flow method

P = TF / C

where

P = vitamin pump speed (mL/minute)
T = theoretical concentration of vitamin in the final product (IU/mL)
F = flow rate of milk (mL/minute)
C = concentration of vitamin premix (or concentration of diluted vitamin solution) (IU/mL)

Example calculation

If the desired theoretical concentration (T) in the final product is 39.975 IU/100 mL of Vitamin D (refer to Table 1), calculate the vitamin pump speed (P) required in order to achieve this desired fortification level.

First, convert the theoretical concentration of vitamin to IU/mL:

39.975 IU/100 mL / 100 mL = 0.39975 IU/mL

P = vitamin pump speed (mL/minute)
T = 0.39975 IU/mL (39.975 IU/100 mL) of Vitamin D
F = 64 L/minute (64 L/minute × 1000 mL/L = 64,000 mL/minute)
C = 9840 IU/mL

P = TF / C
P = [0.39975 IU/mL x 64,000 mL/minute] / 9840 IU/mL
P = 25,584 IU/minute / 9840 IU/mL
P = 2.6 mL/minute

Therefore, the vitamin pump speed needed to achieve a level of 39.975 IU/100 mL of Vitamin D in the final product is 2.6 mL/minute.

For either the batch or continuous flow methods, multiple calculations can be completed to determine the theoretical concentration of the vitamin in the final product (T) based on different operating conditions. 

The theoretical value (T) used in setting up the operating conditions is compared to the calculated value (CV) to determine the correlation between the 2 values on a daily basis.

Calculated values

Calculated Value is used to estimate the actual vitamin concentration in the milk. The use of diluted vitamin premix will affect the calculation of this value, refer to the section Determining the concentration of a diluted vitamin solution . The calculated value should fall within the ranges indicated in Table 1.

CV = CU / Q

where,

CV = calculated level of vitamins in final product (IU/mL)
C = vitamin premix concentration (or concentration of diluted vitamin solution) (IU/mL)
U = total volume of vitamin premix used (or volume of diluted vitamin solution) (mL)
Q = total quantity of fortified finished product (mL)

Example calculation

CV = calculated level of vitamins in final product
C = 50,000 IU/mL of Vitamin A
U = 64.8 mL
Q = 1810 L (1810 L × 1000 mL/L = 1,810,000 mL)
CV = CU / Q
CV = [50,000 IU/mL × 64.8 mL] / 1,810,000 mL
CV = 3,240,000 IU / 1,810,000 mL
CV = 1.79 IU/mL of Vitamin A

This needs to be converted to IU/100 mL

Therefore: 1.79 IU/mL × 100 mL = 179 IU/100 mL

CV = 179 IU/100 mL of Vitamin A

Converting International Units (IU) of Vitamin D to micrograms (µg)

The Vitamin D level can be expressed in either IU or µg. Since 40 IU of Vitamin D is equal to 1 microgram (µg) of Vitamin D, convert from one to the other using either multiplication or division.

Example calculations

To convert IU to µg, divide the number of IU by 40.

For example, 300 IU of Vitamin D is equivalent to 7.5 µg:

300 IU / 40 IU/µg = 7.5 µg

To convert µg to IU, multiply the number of µg by 40.

For example, 2 µg of Vitamin D is equivalent to 80 IU:

2 µg x 40 IU/µg = 80 IU

To convert IU/100 mL to µg/100 mL, divide the number of IU/100 mL by 40.

For example, 30 IU/100 mL is equivalent to 0.75 µg/100 mL:

30 IU/100 mL / 40 IU/µg = 0.75 µg/100 mL