Regarding the sensory evaluation of discoloration, all the samples showed color fading throughout storage, which was delayed to a varying extent by treatment with the different antioxidants.
The most effective treatment was the combination of rosemary and ascorbic acid, which had significantly lower (p < 0.05) discoloration scores than any other treatment even at d 20 of storage.
It was followed by those of either oregano, borage, or rosemary alone, which were given scores < 3 until d 12 of storage. Both control and ascorbic acid-treated samples were given scores > 3 at this same time.
These results showed a good agreement with those of CIE a* values and surface metmyoglobin percentage; a score of 3 ( > 10% discoloration) appeared to correspond approximately to a CIE a* value of 10 and a metmyoglobin percentage of 40%.
Therefore, according to Greene and others (1971), who reported that a consumer panel rejected samples of fresh beef having a percentage of metmyoglobin greater than 40%, control and ascorbic acid-treated patties would be acceptable for only 8 d, while patties treated with rosemary
and ascorbic acid would be acceptable for 16 d, and all other patties for 12 d.