Comparison of acidified and conventional low acid thermal processing of white mushroom in glass jars as influenced by reciprocating agitation

Abstract

The objective of this study was to evaluate the quality advantage that can be gained by combining acidified low-acid food thermal processing (ALTP) (pH < 4.6) and reciprocating agitation thermal processing (RATP) of mushroom. Mushroom was selected as a low acid food which is conventionally subjected to low-acid food conventional thermal processing (LACP) (pH > 4.6). Glass jars were used as containers. LACP was established to target a commercial sterilization process (F_o value of 5.0 min at 121.1 °C), while ALTP was established to get an equivalent pasteurization process (F_o value of 10.0 min at 90 °C). Heat penetration data was obtained to establish the above targeted processes and to assess the influence of processing conditions on the heating rate index and heating lag factor. Once processed, the associated quality parameters were evaluated and compared. Process variables included three processing temperatures (115, 120, 125 °C for LACP and 90, 95 and 100 °C for ALTP) and three RATP conditions (0, 1.0 and 2.0 Hz agitation). The results revealed higher rates of heat penetration and lower processing times for both LACP and ALTP processes as the reciprocation frequency increased. Quality retention advantages were realized as the process temperature was increased in each case. The best advantage was delivered with ALTP. Although the rate of heat transfer was the highest at 2.0 Hz, the best quality was observed at a moderate agitation frequency (1.0 Hz) as product texture breakdown was avoided. This is the first study that combined ALTP and RATP and compared them with LACP.