Questions & Answers
from "On Ice Cream" featured in Dairy Foods magazine
and sourced from "On Ice Cream" technical short courses.

Visual Defects - Pink Discolouration in Vanilla Ice Cream:

Question: What causes pink discoloration in vanilla ice cream?

Answer: Discoloration in vanilla ice cream made using exempt, or so-called natural colors, can occur with changes in mix oxidation/reduction potential. Non-exempt artificial colors do not typically change color with minor changes in pH or acidity and that's one of the benefits of artificial colors.

Annatto (an exempt color), which typically produces a desirable light to golden yellow color in vanilla ice cream, can range in hue from reddish/orange to yellow. If the oxidation/reduction potential of the mix changes due to composition and/or microbiological and chemical contamination, pink discoloration can result. A frequent compositional cause of such discoloration is from use of certain whey ingredients.

Whey can be sourced from different cheeses and processed differently, which impacts coloration with annatto. Interestingly, titratable acidity and pH do not seem to play major roles in ice cream discoloration due to whey. However, whey that is heat processed to improve water immobilization effects in the finished ice cream can cause pink discoloration. It is postulated that whey albumins, which coagulate with heat, indirectly change mix chemistry and are the cause. When low-temperature processed whey is used, pink discoloration does not occur.
Typically, modern whey processing does not apply this excess type of heating.
However, as more concentrated whey protein products are used and higher process temperatures applied, issues related to ice cream color could arise.

It is also important to be aware that whey from cheeses to which color has been added can also discolor ice cream in a different way. Oxidizing agent(s), which are used to bleach out color in the resulting whey, can be carried into the finished whey ingredient. Over use or misuse of the oxidant can also directly or indirectly discolor the finished ice cream due to oxidation of a variety of mix components. This can result in faded, washed out, or in other ways, atypical coloration. It can also cause the development of oxidized flavor in ice cream.

Remember, whey ingredients are limited to 25% of total milk solids nonfat. If that restriction were to be removed, the quality, including the process history, of each individual whey ingredient becomes even more important to consider.