Avocado Ice Cream turned brown

Looking for explanation of a problem I just had. Made Avocado Ice Cream for the first time. (Intended to go with Gazpacho and a Serrano crisp).

Everything was good except that after churning it got put in the chill fridge (3C) instead of the freezer. (I was distracted).

When I realised, I churned it a second time and put it in the freezer overnight. To this point, all still seemed fairly good. Flavour maybe slightly less fresh but quite good, and colour ok. A bit less vibrant than prior to the first churn, but decidedly green.

Next morning however things not so good. Ice cream was decidedly BROWN. Flavour was basically flat.

I don’t plan to repeat this process again, but I would still like to understand what happened. Is it simply the extra air incorporated in the second churning?

Properly made, I’d assume the it can be kept in the fridge at least a few days without adverse impact on colour or flavour. Is that correct?

Method was simply avocados, milk sugar and a little lemon juice puréed then whipping cream folded in and then churned (electric machine about 35 mins)

no idea why that happened but I’d add some salt and more acid and try again.

Buy some powdered citric or ascorbic acid.

In addition to the lemon juice? (1 tbsp per 3-4 avocados and 2.5 cups cream & milk)?

I would use a tsp of citric acid per cup of base and leave out the lemon juice.