I saw many times on tv factories that process food that is natural, so varies in size - strawberries, oranges, peaches, shrimp, you name it. There is an automated scale that drops the correct amount of product on the bags… but how come it can be consistent? If one strawberry weights 17 grams and the other one weights 14, for instance, there will be a variation in weight, as the the machine can’t put half strawberries to add weight, for instance. Is there a tolerance for weight variation? do they fill the “weight gaps” with water?
They have a clever setup where the food going into the processor will be divided into a dozen or so separate chutes, each of which will have its own scale. A computer system will look at the weight of each scale and then choose the combination of chutes whose contents will come out closest to the target weight. So if you need say 50 grams of strawberries, it may pick one that weighs 17, one that weights 14, and one that weighs 19 out of the dozen or so weighed to reach the target weight.
The product that goes through automated lines is as consistently sized as possible. Before it even reaches final packaging, there are sorters that branch the items off to make different types of products so you won’t typically see a large variation in individual pieces like shrimp or strawberries on the packaging stations. There is a ‘good enough’ tolerance level for weight at the final stage of packaging. Smart manufacturers prefer to go slightly over rather than under than the weight stated on the package because there are liabilities for misstating weight on both a regulatory and PR level. That is already built into the manufacturing and financial costs. It all averages out in the end so that any good manufacturer isn’t concerned with any individual package that has a bonus piece.
Even though there may be a difference in individual piece sizes of natural products, it is fairly easy to hit a range of aggregated weight among a bunch of them that are sold to consumers. All you really have to do is keep weighing until the last one goes to or above the target weight. It will be very close in percentage terms to the target.