Consumer preferences, internal color and reduction of shigatoxigenic Escherichia coli in cooked hamburgers

- Burgers in 75% O2 and vacuum was compared for cooked color and STEC reduction.
- Many consumers judge doneness in hamburgers by the internal color.
- Ground beef in 75% O2, but not in vacuum packages, prematurely browned when cooked.
- 75% O2 MAP burgers poses a food safety risk unless its core temperature is measured.
- Measuring temperature is difficult, but only way to assure safe 75% O2 MAP burgers.

The aim of this study was to relate consumer preferences and preparation of hamburgers to color change, internal temperature and reduction of shigatoxigenic Escherichia coli (STEC) serogroups O157 and the “Big Six” (O26, O45, O103, O111, O121, O145) under two ground beef packaging scenarios: 75% O2 MAP and vacuum. 75% O2 MAP hamburgers cooked to 60 °C core temperature appeared done and showed less internal red color (lower a*) than corresponding vacuum hamburgers. Similar STEC reduction (< 4 log10) was found for both hamburgers at core temperatures ≤ 66 °C. In a representative survey (N = 1046) most consumers reported to judge hamburger doneness by the color and many preferred undercooked hamburgers. Premature browning of 75% O2 MAP hamburgers represents a risk of foodborne illness, when considering consumers' food handling practices. The risk is even greater if such ground beef is prepared by consumers who prefer undercooked hamburgers and judge doneness by color.