Average weight is a complex topic that can be difficult to understand, so for that reason, we have devised this blog to explain what it is and if it applies to your business.
If you produce and sell packed food products based on weight, it is a legislative requirement to adhere to the Weights and Measures Act enforced by Trading Standards. The act dictates requirements on units of measurement, specified quantities, packed goods, equipment and records and labelling of packaged goods. Find out more about average weight legislation here.
In this blog, we will focus on packed goods, weighing equipment, and records because this is where our expertise lies.
When selling packaged food products such as rice, meat or soup (based on weight or volume), the product must be packed using the minimum system or the average system.
What is the Minimum System?
Using the minimum system, you can pack the products in accordance with the declared weight on the label, however, the weight of the product can be MORE, but NOT less, than the declared weight using this system. The minimum system is likely to be used in an environment where a low volume of product is produced because each packed product is weighed and checked individually, ensuring it meets the declared weight, however, using this system can result in more giveaway.
What is the Average System?
Using the average system, products must be packed to an average measurement which can be calculated using sampling.
Sampling = a sample of products weighed from a batch. Trading Standards will stipulate the method and frequency of sampling for your business.
When using the Average System, you must also adhere to the Three Packers Rules (explained below).
Manual sampling can be labour intensive, and records must be kept to evidence due diligence. In some instances, an average weight system is used to speed up the process and to eradicate any potential issues caused by human error. In larger manufacturing environments an in-line checkweigher is used to adhere to average weight legislation, which weighs all products within a batch.
The Three Packers Rules
Rule 1 – The average weight of a batch must meet or exceed the target (nominal) weight of the batch.
The average weight of products within a batch needs to be the same, or greater, than the declared weight on the packaging (known as the nominal weight).
For this, you need to add up all the weights of the sample products and then divide the total weight by the number of samples, this gives you the average weight of the batch.
Example: 500 grams, 498 grams, 501 grams = 1499 grams divide by 3 = 499 grams (average weight)
Before we explain Rule 2 and 3, you need to understand TNE (Tolerable Negative Error).
What is tolerable negative error?
When weighing packaged food products, they must not be less, on average, than the weight declared on the label.
As per the table below, a small number of packaged products CAN fall below a certain margin of error, the tolerable negative error (TNE), and no package can be underweight by more than twice the TNE.
T1 = 1x the TNE
T2 = 2x the TNE
Rule 2 – There must be no more than 2.5% of significantly underweight samples/weights (T1 samples).
The second three packers’ rule stipulates that a batch must not have more than 2.5% (or 1 in 40) T1’s in a batch.
The table above allows you to calculate the TNE based on the nominal (declared) weight of your packed product.
Example. Product A = 800 grams, Tolerable Negative Error (TNE) = 15 grams
Rule 3 – There must be no extremely underweight samples at all (T2 samples).
The third rule stipulates that there must be no underweight (T2) samples in your batch. To calculate your T2, it’s simply your TNE x2. So, in this example = 30 grams.
Putting this into context, here is an example:
In this example, the dots represent individual products from a batch that have been weighed. The nominal weight (declared weight) is 800 grams, therefore the T1 is 785 grams and the T2 is 770 grams.
All the dots in green and yellow are acceptable weights in this batch because they are either over or under the nominal weight, but within the T1 boundary (Rule 1 and 2).
The dot in red is an example of a failed batch because the product is extremely underweight (falling into the T2 category).
In order to satisfy average weight legislation, you must provide evidence that your batches pass the three packers’ rules. This can be done manually by paper or electronically using an average weight system.
What is the e mark?
The e mark printed on product packaging determines that the product is packed to average weight legislation.
Average Weight Records
You must keep records of your sample batches for a minimum of one year based on the date the packet is shipped or the ‘use by’ date, whichever is shorter. These records must show that the Three Packers Rules have been met.
Additionally, you must ensure the equipment you use is suitable to meet Trading Standards’ requirements, for example, a domestic scale would not be suitable, the scale you use must be Trade Approved and stamped accordingly. Trading Standards will check the weights and measures of your goods on your production line.