Yes, the audio is wrong in fact. It should be (aklun), not (aklu) here.
The -un vowel is called Tanwin or Nunation. You can consider it as a marker for indefinite nouns (and adjectives), somehow similar to the a/an in English. Since the sentence above is indefinite (the word for food أكل is not defined with AL) then it should be (aklun) أكْلٌ