NS Recipe's translations meet Joomla coding standards. They are all stored in UTF-8 encoded .ini files.
You could modify the .ini files directly. The main drawback is that next time you update your NS Recipes version, all your modifications will be lost.
Fortunately, an elegant way to modify translation exists.
your_locale
/your_locale
com_nsrecipes.iniyour_locale
/your_locale
com_nsrecipes.iniJoomla gives you the opportunity to redefine labels. What you need to do is to go to Extensions > Language Manager > Overrides