Amchoor powder also referred to as mango powder, is a sour and tangy spice powder made from dried unripe green mangoes. It is used to add sourness to recipes, much like vinegar or lemon juice. It is produced in India. I have not known this being used in Yarlpanam at all. It is used to flavour foods and add the nutritional benefits of mangoes when the fresh fruit is out of season.
Making Amchoor powder:
Mangoes are harvested while still green and unripe. They are then peeled, thinly sliced, and sun-dried. The dried slices, which are light brown in colour are available for sale as such and when bought they are ground to a powder. Or else they are ground to a powder and is sold as readymade powder. Usually amchoor powder is readily available to buy.
Uses of Amchoor powder:
It is used in dishes where acidity is required. Used mainly in vegetable dishes, soups, curries, and to tenderize meat and poultry. When amchoor powder is not available lime juice or lemon juice or tamarind pulp can be substituted without much change.