We've all been in this situation: you open the refrigerator to make a sandwich, but the ham is covered with a whitish liquid or is slimy. Here's the dilemma: to eat it or not? Some would say that with a little water the problem is over; but what does science say?

If you've ever wondered what the viscosity is that appears on sausages after several days in the refrigerator, it's lactic acid bacteria that have grown inside the package because of the carbohydrate content in the meat product and because there is high moisture content.

Juan Pedro Camou Arriola, a researcher at the Food and Development Research Centre (CIAD) and an expert in meat products, explained that these are benign bacteria such as lactobacilli, which, although in low concentrations are not harmful to our health, do produce an odor and taste with acidic overtones.

The growth of these bacteria inside the package acts as an inhibitor of pathogenic bacteria (which cause illness in the consumer) and inhibits bacteria that break down food such as Pseudomonas, which cause putrefying odors.

As to whether it is advisable to consume the ham once it has this viscosity, the first answer is no, as it is impossible to predict what effect it will have on the consumer because it is not known that other types of bacteria have grown.

However, if you insist on eating it, and when you wash it with water the bad smell and taste disappear, the most likely thing is that it will not cause you any harm. These types of lactic acid bacteria are the ones used commercially to ferment food products such as salami, yogurt, and ripened cheese, among others.

On the other hand, if you don't give up your intention to eat the processed meat, and after rinsing it with water the decomposed aroma doesn't disappear, you should not consume it, since the risks of contracting a gastrointestinal infection are higher.

Camou Arriola pointed out that, to be properly preserved, the sausages must maintain the "cold chain"; in other words, they must be kept at temperatures of 0 to 2 degrees centigrade, from the moment they are packaged, transferred to the supermarkets, stored in commercial display cases and until they reach the end consumer.

It is the rupture of this chain (exposure to temperatures above 4°C), which causes the sausage to release water and accelerate the process of decomposition.

The average shelf life of most sausages is between forty-five and sixty days (from the time they are produced); however, interruption of the cold chain and opening of the package shorten this period, especially in regions where temperatures are higher, and in homes where the refrigerator is not set at the right temperature (6 degrees).

Finally, the researcher recommended that, if people use sausages for the preparation of lunches, such as sandwiches, it is necessary to ensure that these are refrigerated or, at least, stored in thermal packaging that preserves the cold, until the time of consumption.