Viability of Molds and Bacteria in Tempeh Processed with Supercritical Carbon Dioxides during Storage

Application of supercritical carbon dioxide for processing of food products has an impact on microbial inactivation and food quality. Tis technique is used to preserve tempeh due to no heat involved. Te quality of tempeh is highly infuenced by mold growth because of its role in forming a compact texture, white color, and functional properties as well as consumer acceptance. Tis study aims to observe viability of molds and bacteria in tempeh afer processed with supercritical CO2 and to determine the best processing conditions which can maintain mold growth and reduce the number of bacteria in tempeh. For that purpose, tempeh was treated using high pressure CO2 at 7.6 MPa (supercritical CO2) and at 6.3 MPa (sub/near supercritical CO2) with incubation period of 5, 10, 15, and 20 min. Te best treatment obtained was used to process tempeh for storage study. Te results showed that there was a signifcant interaction between pressure and incubation period for bacterial and mold viability at � >0.05. Reduction of bacteria and molds increased with longer incubation period. Molds were undetectable afer treatment for 20 min with either supercritical CO2 or sub-supercritical, and bacteria signifcantly reduced up to 2.40 log CFU/g. On the other hand, sub-supercritical CO2 for 10 min was the best processing method because molds survived 4.3x104 CFU/gram afer treatment and were able to grow during storage at 30∘ C, producing white mycelium as indicated by increasing the �∗ color value and tempeh acceptability. Te inactivation of mold was reversible causing it to grow back during storage under suitable conditions. Tempeh matrix composition can provide protection against the destructive efects of supercritical CO2. Gram-positive bacteria were more resistant than Gram-negative. In conclusion, sub-supercritical CO2 can act as a method of cold pasteurization of tempeh and can be used as an alternative method to preserve tempeh.