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

Abstract

Application of supercritical carbon dioxide for processing of food products has an impact on microbial inactivation and food quality. This technique is used to preserve tempeh due to no heat involved. The quality of tempeh is highly influenced by mold growth because of its role in forming a compact texture, white color, and functional properties as well as consumer acceptance. This study aims to observe viability of molds and bacteria in tempeh after 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. The best treatment obtained was used to process tempeh for storage study. The results showed that there was a significant interaction between pressure and incubation period for bacterial and mold viability at ρ>0.05. Reduction of bacteria and molds increased with longer incubation period. Molds were undetectable after treatment for 20 min with either supercritical CO2 or sub-supercritical, and bacteria significantly 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 after treatment and were able to grow during storage at 30°C, producing white mycelium as indicated by increasing the L⁎ color value and tempeh acceptability. The inactivation of mold was reversible causing it to grow back during storage under suitable conditions. Tempeh matrix composition can provide protection against the destructive effects 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.

Quality and Shelf Life of White Shrimp (Litopenaeus vannamei) Processed with High-Pressure Carbon Dioxide (HPCD) at Subcritical and Supercritical States

“…A similar finding reported that the fat content of Nila tilapia was not affected by scCO 2 from 80 to 90 bars at 40°C [29]. On the contrary, fat content in tempeh reduced at 1100 psi at 31°C [30]. Fat in foods is lipophilic and soluble in supercritical CO 2 ; therefore, it decreased during HPCD processing.…”

“…In contrast, the number of microbes in tilapia decreased by 2 log cycles at a pressure treatment of 80 bar reported by Sugiharto et al [29]. Meanwhile, Kustyawati et al [30] found that tempeh treated with 900 psi significantly (p ≤ 0.05) reduced the number of microbes by 2 logs. e type and chemical contents of products processed with supercritical CO 2 could be the reason for inhibiting microbiological inactivation in treated shrimps in this study.…”

Microbiological and Biochemical Tests on Tempe Production Using Tempe Mold Innovation

“…Meanwhile, for the overall compactness of the samples, both treatment and control showed compact results with very tight mycelium so that the soybean seeds condensed to have an appearance like tempeh. These results indicate that all samples exhibit the ideal characteristics of tempeh, which have evenly distributed white mycelium with a compact appearance (Kustyawati et al, 2018).…”

Shelf life of tempeh processed with sub-supercritical carbon dioxides

“…Tempeh, in the form of a cylinder with a diameter of 35 mm and a length of 100 mm, fermented for 36 hours at 30 °C, was obtained from the Center of Home Industry Tempeh Making Palembang, Indonesia, placed in a cooler box and carried to the laboratory for direct processing (Kustyawati et al, 2018).…”