The juice label declared 30 mg of vitamin C per 100 ml. At month six of a nine month shelf life, a retailer’s routine test found 11. Nobody had cheated. The dosing sheet said 30 mg, the operator added 30 mg, and the vitamin spent six months in a clear bottle doing what vitamin C does. No one had calculated a vitamin overage, so the label claim did not last the shelf life.
In short
- A declared vitamin value must be true on the last day of shelf life, not on the day of filling.
- Vitamins degrade with heat, light, oxygen, pH and time. Each vitamin has its own main enemy.
- Overage is the extra you add at manufacture so that the declared amount is still there at the end. It is calculated from measured losses.
- Loss often follows a roughly first order curve, and accelerated storage trials at higher temperatures let you estimate it before a full shelf life has passed.
- Packaging that blocks light and oxygen reduces the overage you need. Unit errors (mg, µg, IU) ruin more declarations than chemistry does.
The juice is an invented example, but the pattern is common enough that module 3 of the Advanced Food and Beverage Labelling Course from ASC Food Safety Training has a case study called “The vitamin that vanished”. The course costs R2 950. A failed retailer test costs a reformulation at the very least.
Does a declared vitamin value have to hold until the end of shelf life?
A declared vitamin value has to be true for as long as the product is on sale, because a consumer may buy it on the last day before the date mark. The Foodstuffs, Cosmetics and Disinfectants Act 54 of 1972 prohibits false or misleading descriptions. Inspectors and retailers sample from the shelf, not from your filler.
If you make a claim such as “source of” or “high in” under R146 of 2010, the qualifying amount also has to survive. Check the current regulation text for the conditions and any tolerances before you set the declared value.
The label is a promise about the last day of shelf life. The dosing sheet is written on the first.
Why do vitamins disappear from a product during shelf life?
Vitamins are reactive organic molecules, and food is a reactive place. Heat during processing, light through the pack, oxygen in the headspace and dissolved in the product, pH, trace metals such as copper and iron, and plain time all break them down. Each vitamin has a main weakness, so each needs a different defence.
| Main enemy | Packaging or process answer |
|---|---|
| Vitamin C (ascorbic acid) | |
| Oxygen and heat, speeded up by copper and iron | Deaerate, minimise headspace, oxygen barrier pack, dose after the harshest heat step where you can |
| Riboflavin (B2) | |
| Light. It is fairly heat stable | Opaque or pigmented packaging, sleeves, cartons |
| Vitamin A | |
| Light and oxygen | Light and oxygen barrier, protected (encapsulated) forms, antioxidants where permitted |
| Thiamine (B1) | |
| Heat, especially at higher pH, and sulphite | Gentler heat treatment, keep away from sulphited ingredients |
| Folate (folic acid) | |
| Heat, oxygen and light. Added folic acid holds up better than natural folates | Control the heat step, limit oxygen, measure the process loss |
Nowhere does the table say “add more”. Adding more is the last step, after you have removed as much of the enemy as the product and the budget allow.
What is vitamin overage and how do you calculate it?
Vitamin overage is the amount of a vitamin added above the declared value so that, after processing losses and storage losses, the declared amount is still present at the end of shelf life. You calculate it by measuring the fraction that survives each stage, multiplying those fractions together, and dividing the declared value by the result.
Storage loss is often close to first order: the product loses a roughly constant fraction of what remains in each equal period, so the natural log of concentration plotted against time is close to a straight line. The slope is a rate constant, and a rate constant lets you predict.
Worked example
Vitamin C in a juice blend, nine month shelf life, declared 30 mg per 100 ml.
Measured: pasteurisation destroys 10 percent, so 0.90 survives. In storage at 25 °C the product loses 20 percent every three months, so 0.80 survives each quarter.
Surviving storage over nine months: 0.80 x 0.80 x 0.80 = 0.512. Surviving overall: 0.90 x 0.512 = 0.461.
Dose needed: 30 / 0.461 = 65 mg per 100 ml. That is an overage of about 117 percent, before any margin for batch variation and laboratory uncertainty.
Now change the pack and deaerate the juice so that only 10 percent is lost per quarter: 0.90 x 0.90 x 0.90 = 0.729, overall 0.656, dose 46 mg, overage about 52 percent. The better pack cuts the ascorbic acid dose by almost a third.
Two cautions. Real vitamin C loss in juice is often faster at the start, while dissolved oxygen is being used up, and slower afterwards, so fit the curve to your own data and do not trust one early point. And overage has a ceiling. Taste, colour, cost and, for vitamins such as A and D, safety all limit how much extra you can add.
That was one vitamin, and a fortified product carries a premix of them. Module 3 of ASC’s advanced labelling course with vitamin overage modelling includes a multi vitamin premix overage worksheet, so you work through the whole premix at once.
Start the Advanced Food and Beverage Labelling Course, R2 950
How do accelerated storage trials estimate vitamin loss before shelf life ends?
In an accelerated storage trial you store the product at two or three raised temperatures as well as the normal one, measure the vitamin at intervals, and work out a rate constant at each temperature. Reactions run faster when warm in a predictable way, described by the Arrhenius equation, so the warm results let you estimate the rate at normal storage temperature within weeks.
In plain words: plot the log of each rate constant against one over the absolute temperature, draw the line, and read off the rate at 25 °C. The popular rule that reactions double in speed for every 10 °C is only a rough guide, which is why you measure.
Accelerated work has limits. Push the temperature too far and you trigger reactions that never happen on a shelf, and heat tells you nothing about light. Always confirm with a real time trial, in the real pack, tested by a competent laboratory. A recipe change puts the stability data out of date too. See what a recipe change should trigger for the label and shelf life.
How much does packaging matter for vitamin stability?
For light sensitive and oxygen sensitive vitamins, packaging often matters more than the recipe, because it decides how much light and oxygen reach the product over months. Riboflavin is the classic case. Milk in a clear bottle under display lighting loses riboflavin and picks up off flavours as it breaks down. The same milk in an opaque or pigmented pack does not.
For oxygen, glass and metal are effectively complete barriers. Plastics vary widely and let oxygen through slowly over the whole shelf life, and headspace volume, closure liners and nitrogen flushing all count.
Ask the packaging supplier for light and oxygen transmission data on the actual pack. If marketing wants a clear bottle, put a number on what it costs in overage and let them decide with the figure in front of them.
Which unit errors wreck a vitamin declaration?
The unit error that wrecks a vitamin declaration is mostly the thousandfold one. A milligram is 1 000 micrograms, and vitamins are declared in one or the other depending on the vitamin, so a premix specification in mg copied into a panel line in µg produces nonsense. International units add a second trap, because the conversion is different for every vitamin.
1 000
µg in one mg
40 IU
per µg of vitamin D
0.3 µg
retinol per IU of vitamin A
About 1/3
of ferrous fumarate is iron
Beta carotene converts to vitamin A at a different figure again. Minerals have their own version of the problem: the label declares the element, not the salt. Ferrous fumarate is only about one third iron by mass, so 30 mg of the compound is nowhere near 30 mg of iron. Every one of these errors also flows straight into the % NRV column, which is why unit checks belong on the food label sign off checklist, next to the arithmetic covered in how to calculate a nutrition information table.
What does the Advanced Food and Beverage Labelling Course cover, and what does it cost?
The Advanced Food and Beverage Labelling Course is an advanced online food labelling course from ASC Food Safety Training. It costs R2 950 and is self paced, with seven modules. Module 3 is the vitamin module: fortification in South Africa, stability kinetics, overage modelling, units and conversions, and Arrhenius estimation.
| Course | Advanced Food and Beverage Labelling Course |
|---|---|
| Provider | ASC Food Safety Training |
| What you take back to work | Overage modelling, Arrhenius shelf life estimation, a multi vitamin premix overage worksheet and a mineral interaction matrix |
| Level | Advanced. Third step in the ASC labelling ladder |
| Time | Seven modules, worked through at your own speed |
| Price | R2 950, paid once. Card or EFT through PayFast |
| Format | Online, self paced, lifetime access |
| Assessment | A knowledge test for each module and a course assessment |
| Certificate | Certificate of completion |
| Who it is for | People who formulate, check and sign off fortified and claim bearing products |
Enrol in the Advanced Food and Beverage Labelling Course, R2 950
Questions people ask before they enrol
How much does the Advanced Food and Beverage Labelling Course cost, and how long does it take?
R2 950, paid once by card or EFT through PayFast. That covers seven online modules, a knowledge test for each module, a course assessment, lifetime access to the material and a certificate of completion. There is no fixed timetable: the course is self paced, so you work through it around production.
Do I need a chemistry degree to follow the vitamin stability module?
No, but it is an advanced course. It is the third step after Essentials of Food Labelling Claims (R1 250) and Labelling Claims and Regulatory Framework (R1 750). Module 3 works through kinetics, Arrhenius estimation and minerals on an elemental basis, with a premix overage worksheet, a mineral interaction matrix and a case study.
How is the course assessed, and do I get a certificate?
Each of the seven modules has a knowledge test and there is a course assessment at the end. You receive a certificate of completion, and lifetime access means you can return to the worksheets later.
Can I enrol from outside South Africa?
Yes. Prices are in rand, the course page shows an indicative equivalent in US dollars, euros and pounds, and payment settles in rand. The regulatory content is South African, while the stability chemistry applies wherever you manufacture.
The juice in the opening went back to development. The team measured the pasteurisation loss, ran a storage trial, moved to a better barrier bottle and set an overage they could defend with data. All of it was paid for after the retailer found the problem. Price any one item and put it next to R2 950. Enrol in the Advanced Food and Beverage Labelling Course (R2 950) before your next fortified launch and set the overage with the worksheet open. The food labelling training hub lists the courses that lead up to it.
This article is training material, not legal advice. Check the current regulation text where a number matters. The course is an independent training product and is not approved or endorsed by any government department or regulator.