twigfiddle.com - Fiddle dec59b v1 - Created on April 7, 2021 17:09

File

{% set product = "name: smoothie, ingredients: milk, orange" %}

{% set items = [] %}

{% for item in product|split(',', 2) %}
    {% set tmp = item|split(':') %}
        
    {% set option = tmp[0] %}
    {% set values = [] %}
        
    {% for value in tmp[1]|split(',') %}
       {% set values = values|merge([ value, ]) %}
    {% endfor %}    
    
    {% set items = items|merge([ {'option': option, 'values': values,}, ]) %}
{% endfor %}

{% for item in items %}
    - Option: {{ item.option }}
    - Values:
    {% for value in item.values %}
        - {{value }}
    {% endfor %}
{% endfor %}

=======================================================
Full example with multiple products:

{% set products = [] %}

{% for string in products_raw %}
    {% set product = [] %}
       
    {% for item in string|split(',', 2) %}
        {% set tmp = item|split(':') %}
        
        {% set option = tmp[0] %}
        {% set values = [] %}
        
        {% for value in tmp[1]|split(',') %}
            {% set values = values|merge([ value, ]) %}
        {% endfor %}    
    
        {% set product = product|merge([ {'option': option, 'values': values,}, ]) %}
    {% endfor %}
    
    {% set products = products|merge([ product, ]) %}
{% endfor %}

{% for product in products %}
    {% for item in product %}
    - Option: {{ item.option }}
    - Values:
    {% for value in item.values %}
        - {{value }}
    {% endfor %}
{% endfor %}    
----------------------------------
{% endfor %}

Format

products_raw:
    - 'name: smoothie 1, ingredients: milk, orange'
    - 'name: smoothie 2, ingredients: milk, banana'
    - 'name: smoothie 3, ingredients: milk, orange, pineapple'