No. 1: Can preservatives slow bacterial growth in stored goat colostrum?

Anastasio Argüello — Mon, 02 Nov 2026 00:00:00 GMT

The paper: Liang F, Capdevila Ospina K, Cameron AWN, DiGiacomo K, Zamuner F (2026). Evaluating the temperature-dependent effects of 3 preservative treatments on bacterial growth in raw goat colostrum. Journal of Dairy Science. https://doi.org/10.3168/jds.2026-28527

What did they ask?

Goat kids are born without antibodies: the goat placenta does not let them through, so all early immunity depends on colostrum. But raw colostrum can become contaminated with bacteria during storage. Those bacteria can make kids sick and may also interfere with immunoglobulin absorption in the gut.

Refrigeration, freezing or pasteurisation help, but they are not always practical on farm. Chemical preservatives for colostrum have been tested in cattle, but hardly at all in goats. The authors wanted to know whether three food-grade preservatives slow bacterial growth in goat colostrum, both refrigerated and at room temperature.

What did they do?

They collected fresh colostrum from about 27 does on two commercial farms in Victoria, Australia, keeping only good-quality colostrum (Brix of at least 20%), and pooled it into a single batch. They split it into four groups:

no preservative (control),
potassium sorbate at 0.5%,
sodium benzoate at 0.5%,
sodium lactate at 0.3%.

Samples were stored at 4 °C for one week (up to 168 hours) and at 25 °C for two days (up to 48 hours), mimicking the fridge and colostrum left out during collection or transport. At set times they counted coliforms, Escherichia coli and total bacteria, and measured pH.

What did they find?

Bacterial counts are on a log scale: a difference of 1 log means 10 times more bacteria, and 3 log means about 1,000 times more.

In the fridge (4 °C). All samples stayed stable for the first two days. By the end of the week, untreated colostrum had reached almost 7 log coliforms. With sorbate or benzoate, coliforms stayed close to the starting level (about 4 log), roughly 1,000 times fewer than the control. Total bacteria were also more than 1.3 log lower with these two preservatives. E. coli stayed low in every group, with or without preservative.

At room temperature (25 °C). Without preservative, bacteria took off: coliforms reached 6.7 log at 12 hours and total bacteria exceeded 9 log at 24 hours. Sorbate and benzoate made a difference as early as 6 hours, and at 12 hours coliforms were 2.4 to 2.9 log below the control. With them, E. coli stayed near or below the detection limit.

Sodium lactate did not work. At 0.3%, it followed almost the same course as the control at both temperatures.

Why does it matter?

The study supports a two-barrier approach. The first and main barrier is cold: temperature had the biggest influence on bacterial growth. The second would be sorbate or benzoate, most useful in two common farm situations: the first hours when colostrum sits at room temperature before it reaches the fridge, and when it is kept refrigerated for longer than planned.

The authors are clear: these preservatives reduce risk, but they do not replace good hygiene or the cold chain.

Limitations

A single batch of colostrum. Everything was done with one pooled sample from two farms, which in practice equals one biological replicate. The authors themselves regard the results as preliminary.
Immunoglobulins were not measured. We do not know whether the preservatives affect IgG in goat colostrum, or whether they improve immunity in the kids that drink it.
Little E. coli to begin with. With such low counts, it cannot be claimed that these preservatives work specifically against E. coli.
Laboratory conditions. They do not capture real differences in hygiene, equipment and contamination between farms.

Licence: CC BY 4.0.

Goat Science (English)