Materials

The materials utilized in this study consisted of milkfish, squid, grilled chicken, rendang, chicken satay, retort bags, and iron glue. The necessary equipment includes a Rex C100 PID Thermostat, a single fiber cable, a heat resistant cable, cable connectors, sockets, cable skuns, a K type thermocouple with a spade type connector, a 25 Liter Nagami brand pressure cooker, a stainless steel net for the pressure basket cooker, a gas stove, a furnace, a gas hose and regulator, a gas cylinder, a rubber pressure cooker hole cover, and a stainless steel plate.

Measurement of Heat Distribution in a Pressure Cooker

The heat distribution test is conducted just once for a certain product (Yudianto, Dewanti-Hariyadi, Sukarno, Nur, & Purnomo, 2023). However, in this experiment, five heat distribution tests will be performed on samples of milkfish, squid, grilled chicken, rendang, and chicken satay. Evaluate the thermal dispersion by conducting experiments on a domestic pressure cooker with a volume of 25 liters. A hole is added to the pressure cooker lid to accommodate the thermocouple cable. The pressure cooker basket is organized with ordinary samples and packages without samples, the latter of which are equipped with a thermocouple. The packing without samples that have been given a thermocouple are positioned in a spread-out manner at the bottom, edge, middle, and top of the basket. The water is heated within a pressure cooker until it reaches its boiling point. Next, the basket containing the sample and packing, together with the thermocouple, is immersed in boiling water within the pressure cooker. The pressure cooker lid is securely fastened, with the steam weight removed to allow for venting. At this point, the temperature is measured using the thermostat. Once the water vapor reaches a stable state, the ballast is sealed and the time it takes to release the vapor is recorded. The heating operation is continued until the temperature recorded on the thermostat monitor remains constant for a duration of at least 30 minutes. Subsequently, the process of heating is halted.

Validation of Sterilization Process

The sterilization technique involves utilizing a household pressure cooker with a 25-liter capacity, as demonstrated in the heat distribution test. The pressure cooker basket is organized with both regular samples and samples equipped with thermocouples. The thermocouple-equipped samples are strategically positioned at the bottom, edge, middle, and top of the basket. This treatment is administered singularly at the onset to validate the heat distribution outcomes of the preceding pressure cooker. Only one product is equipped with a thermocouple in the coldest area of the confirmed pressure cooker for all future procedures. This ensures continuous monitoring and validation of the commercial sterilizing process. The sterilizing process is conducted using the same method as the heat distribution test for a pressure cooker.

General Method

In order to obtain the F₀ value in real-time, one can immediately input the formula for computing the F₀ value into Microsoft Excel. Each time there is a fluctuation in temperature over a given time period, it will be directly recorded in Microsoft Excel, enabling the automatic calculation of the F₀ value. The attainment of an F₀ value of 3.0 minutes will indicate the successful completion of the commercial sterilizing process. Typically, the duration of the operation is extended by a factor of 2 to 3 in order to account for any unforeseen cold spots in the pressure cooker. The sterilization procedure involves the complete inactivation of Clostridium botulinum spores by subjecting them to a standard inactivation of 12 log cycles at a reference temperature of 121.1°C (Yudianto, Dewanti-Hariyadi, Sukarno, Nur, & Purnomo, 2023). The formula for assessing the effectiveness of the sterilization procedure is determined by the Z value, which is set at 10°C (Jung, Lee, & Yoon, 2023). That equation was based on the integration between the need of 12 log cycles of Clostridium botulinum spores and first order kinetic model for bacteria inactivation by thermal process.

Processing time for sterilization process is commonly known by F.

the first order kinetic model follows (Sun, Xu, Wu, Shen, & Zhan, 2023):

k(N) = - d(N)dt

log(NtN0)=-∫t0tt1Ddt --> DT=D0×10250-TtZ

Back to --> F0=log1013101×D0

logN0Nt=∫t0tt1D0×10250-TtZdt

T is temperature (°F). N is total bacteria (CFU/mL). D is time to change 1 log cycle of bacteria inactivation (minute). Z is the temperature change for 1 log cycle of D value change (°F).

Ball Formula Method

To predict temperature fluctuations in the pressure cooker caused by unforeseen circumstances, it is necessary to conduct a scheduled sterilization process adequacy test. The scheduled process is determined by the temperature and duration of the sterilization process in a pressure cooker. This is calculated using various variables in the ball formula to achieve a specific sterilization value. Therefore, if the temperature of the pressure cooker changes, it only needs to determine the corresponding duration for the sterilization process under the new conditions (Praharasti et al., 2020). The current temperature of the pressure cooker in operation. In order to ascertain the variables in the ball formula, it is imperative to plot the heat distribution in the sterilized material by employing the subsequent unstable heat transfer equation (Hariyadi, 2019):

Tr-T=Tr-Ti*exp-K*t         regarding the exponential model

LogTr-T=LogTr-Ti-K2,303*t      regarding the linear models

The K value will be similiar for a similiar product, size, and packaging. By graphing the temperature change data for each change in heating time using either the exponential or linear model mentioned before, we may determine various variables in Table 1, specifically:

By utilizing the thirteen variables mentioned, it is possible to determine the specific combination of temperature and processing time for sterilization in a pressure cooker. This combination will result in a desired F₀ value, based on the interaction of these variables. The F₀ value calculation using the Ball formula method is determined based on the lowest F₀ value obtained from one of the thermocouples, which measures heat penetration, in the general method. It is hypothesized that if the lowest F₀ value can produce a satisfactory model and be utilized, then all thermocouples that generate F₀ values in the general method will also yield satisfactory models and be usable.

Measurement of Heat Distribution and Products in Pressure Cookers

Figure 2 displays temperature data of pressure cookers and various products used in the food service business. The assessed goods were milkfish, squid, grilled chicken, rendang, and chicken satay. Figure 1 displays various products as samples including rendang, grilled chicken, milkfish, chicken satay, and squid, respectively. The domestic pressure cooker utilized ensured consistent heat distribution, maintaining a temperature range of 246.2°F during the testing of the five different products. The sterilizing process in the household pressure cooker is depicted in Figure 1G. The coolest side of the milkfish, squid, grilled chicken, rendang, and satay product can reach maximum temperatures of 235.4, 242.6, 233.6, 235.4, and 221°F, respectively. The thermal conductivity of the packing material is also a determining element in its ability to transfer heat to the coldest side of the product. Figure 1F illustrates that the packaging employed is a retort pouch, which facilitates the transfer of heat from the external environment to the coldest part of the product. It could transfer the heat well (Fardella et al., 2021).

Upon examining Figure 2, it becomes evident that all goods, with the exception of chicken satay, are subjected to heat that is nearly identical to the temperature of a pressure cooker. The monitored temperatures of chicken satay products typically do not exceed 212°F, however they may temporarily surpass this threshold for a brief period. Nevertheless, the outcome of this heat penetration will directly impact the attainment of the F₀ level. If the temperature at the coldest point of the product cannot exceed 212°F within a specific duration, the reference temperature of 250°F must be taken into account. This difference is important in determining a F₀.

Figure 1

The Activities Included are as follows: Rendang (A), Grilled Chicken (B), Milkfish (C), Chicken Satay (D), Squid (E), Installation of Thermocouples on 5 Products (F), and Sterilization Process using Household Pressure Cooker (G).

Figure 2

Graph Depicting the Correlation between Temperature of a Pressure Cooker and the Resulting Product as a Function of Time.

F₀ Value by General Method

Figure 3 displays the outcomes of the calculation of cumulative F₀ variations over time. The chart illustrates that four goods, specifically milkfish, squid, grilled chicken, and rendang, have exceeded the permissible commercial sterilizing criteria in terms of their cumulative F₀ values. The duration is 3.00 minutes. Based on the statistics provided, it is evident that all four goods have successfully undergone commercial sterilizing. In contrast to the other goods, the chicken satay products failed to achieve a cumulative F₀ value of 3.00 minutes. This outcome is predictable based on the information shown in Figure 2, which indicates that chicken satay products are unable to tolerate temperatures below 212°F for an extended duration.

Figure 3

Plot Illustrating the Correlation between F₀ and Time for Each Product.

By monitoring real-time temperature changes, the sterilization process may be tested for effectiveness. This allows for the determination of the final F₀ value, which is displayed in Table 2. Every product, except for chicken satay, has undergone commercial sterilization based on the entire process duration (B value) at a relative operating temperature of 246.2°F in the pressure cooker. Due to the low temperature experienced by chicken satay products at their coldest point, it is not possible for them to achieve commercial sterility within 1-3 hours of processing. Due to the excessive duration required for commercial sterilization of chicken satay product, it is no longer essential to determine the F₀ value for this particular product.

F₀ Value by Ball Formula Method

By attaining commercial sterilization for milkfish, squid, grilled chicken, and rendang goods, it becomes possible to determine the F₀ values of these four products using the Ball formula approach. Calculating the F₀ value using the Ball formula approach is not feasible for chicken satay products due to the fact that the general method has not yet attained commercial sterilization. In order to calculate the F₀ value using the Ball formula approach, it is necessary to have the results of calculating the F₀ value using the general method. This is necessary to verify the usability of the variables Fh and jI in the Ball formula method.

Figure 4

Graph Depicting the Relationship between Temperature (Tr) and Time in The Heat Penetration of Milkfish.

Figure 5

Graph Depicting the Relationship between Temperature (Tr) and Time in The Process of Heat Penetration in Squid.

The milkfish products have known Fh and jI values, as shown in Figure 4. Upon examining Table 3, it becomes evident that the F₀ value obtained using the Ball formula approach is higher than the F₀ value obtained using the general method. Figure 4 becomes invalid due to the inability to utilize the Fh and jI variables in plotting the difference in pressure cooker temperature and product temperature against process time. This occurs due to the inadequate visibility of the linear heat penetration graph within the product.

Figure 6

Graph Depicting the Relationship between Temperature (Tr) and Time in The Heat Penetration Process of Grilled Chicken..

The slow heat conduction from the tool to the coldest part of the product often affects the visibility of linear sections. The sluggish heat penetration can be affected by the slow rate at which the heating/sterilization device reaches temperatures that are similar to the standard commercial sterilization temperature, specifically 250°F. In addition to the tool's characteristics, the product itself also influences the speed at which heat is able to penetrate. Products with a high water content, such as gravy, typically possess favorable heat penetration qualities. Conversely, if the product has little moisture content, it will impede the transfer of heat into the product (Mahir, Maakoul, Khay, Saadeddine, & Bakhouya, 2021). The presence of oil in food also enhance the heat transfer in that product (Hoffmann et al., 2016).

Despite the poor rate of heat penetration, commercial sterilizing can still be accomplished for milkfish products by extending the processing time. A similar occurrence is observed with grilled chicken product as well. Grilled chicken product have undergone commercial sterilizing. Nevertheless, the F₀ calculation findings obtained using the Ball formula approach are identical to those for milkfish products. Specifically, the F₀ value obtained using the Ball formula method is greater than the F₀ value obtained using the general method. Based on the outcomes of these computations, it is not now possible to utilize the variables Fh and jI depicted in Figure 6 .

Figure 7

Graph Illustrating the Relationship between Temperature (Tr) and Time in The Process of Rendang Heat Penetration..

When the squid product is heated, a fractured linear section becomes visible. The fractured segment is affected by the nature of the squid, which undergoes solidification when exposed to heat. The squid's texture undergoes a process of hardening, which results in alterations in the speed at which heat is absorbed. The thermal conductivity of the tender squid is high, resulting in a rapid rate of heat transfer as indicated by the steep incline of the first heating curve. As the squid's texture solidifies, the rate at which heat is absorbed slows down, as seen by the gradual slope of the heat penetration curve shown in Figure 2. Figure 5 illustrates the process of determining the Ball formula variable for calculating the F₀ value using a broken curve. In addition to Fh and jI, the broken curve contains two extra variables, F2 and Xbh, which arise from the intersection of the linear lines in the two broken linear sections. Upon doing the calculations outlined in Table 4, it is evident that the value of F₀ obtained through the Ball formula approach surpasses the value obtained through the general method. Consequently, the variables Fh, jI, F2, and Xbh depicted in Figure 5 are deemed unsuitable for usage.

The variables in the Ball formula for calculating outcomes for milkfish, grilled chicken, and squid product are currently not applicable for scheduled process calculations. Based on these findings, it is advisable to maintain the three product in a sterilized state at the exact same temperature settings as during the sufficiency test of the sterilization process. Essentially, the planned process aims to observe and predict the B and Pt values as they approach a specific F₀ value in response to abrupt fluctuations in temperature. The inability to ascertain F₀ using the Ball formula does not imply the failure of commercial sterilization, as the Ball formula is a theoretical framework that requires confirmation for its application.

Table 3 demonstrates that theF₀ values obtained using the Ball formula technique are lower than those obtained through the standard method for rendang. Therefore, the variables Fh and jI depicted in Figure 7 can be utilized to compute scheduled processes. The validation of the Fh and jI variables is performed by comparing the F₀ value using the Ball formula method with the values obtained from the Ball formula and general methods. If the computed value of F₀ using the Ball formula approach is less than F₀ using the general method, variables can be employed. This comparison suggests that if the F0 value obtained using the Ball formula approach is approximately 3.00, then the original F₀ value must be satisfactory, as it exceeds the Ball formula method and will be significantly larger than 3.00. If the calculated value of F₀ using the Ball formula approach exceeds the value of F₀ obtained using the general method, there is a difference. This situation poses a significant risk, as an F₀ number that is in close proximity to 3.00 when utilizing the Ball formula approach indicates that the initial F₀ value may be less than 3.00, hence failing to achieve commercial sterilization.

Schedule Processes

The calculations for the scheduled process of rendang are presented in Table 5. Accurate process calculations necessitate the utilization of a consistent value for j. The constant j remains constant as long as the product and packaging conditions remain the same as during the sterilizing adequacy test. Once the constant j is acquired, the values of B and Pt can be calculated based on the desired F₀ value for alternative changes in process temperature. This computation involves determining the inverse of the calculation used to find the value of F₀, which is already known for the given values of B and Pt. Table 6 provides a concise overview of the planned procedure for sterilizing rendang using a pressure cooker commonly seen in households. There are nine distinct variations in process temperature that serve as benchmarks for the sterilization process. These variations account for the potential changes in temperature that may occur due to a decrease in equipment performance. There are nine temperature variation options available, and each option provides information on the B and Pt values required to produce the estimated F₀ value.

Typically, products that have performed commercial sterilizing processes can be stored at room temperature for over a year without deterioration (Xue et al., 2023). This one-year guarantee is based on the principle of 12 log cycle inactivation of Clostridium botulinum spores, hermetic packaging, and a low level of chemical deterioration in quality. The 12-log cycle inactivation of Clostridium botulinum spores can be considered an opportune. During a single batch of commercial sterility food production, there is a one in one billion chance that one product may get infected with Clostridium botulinum spores, provided the initial bacteria 1000. These findings suggest that when the quantity of commercially sterilized food products manufactured is limited to 10,000 units, the likelihood of contamination by Clostridium botulinum spores is 0.00001 spores. This situation implies that there is a significant likelihood of sterility in all manufactured products.

Following the sterilization procedure, it is enclosed in hermetic packaging. Hermetic packaging refers to a type of packaging that is completely sealed, preventing any exchange of air between the inside and exterior of the package (Borém et al., 2021). This will preserve the sterility of products that have undergone commercial sterilizing processes, ensuring a minimal risk of microbiological contamination, particularly from Clostridium botulinum spores. Once the threat posed by bacteria is successfully mitigated, the duration for which the product remains suitable for consumption will no longer be influenced by microbial activity, but rather by the activity of chemical constituents present in the food. Under optimal food storage conditions, the rate of food decay is typically low, resulting in a significantly prolonged time for food to spoil due to the chemical processes occurring within it (Afriyie et al., 2022). Commercial sterility of food products typically exhibit a prolonged shelf life at ambient temperature, often exceeding one year.

The commercial sterility in this research was carried out by a thermal process. Several advantages of this commercial sterility process include extended shelf-life at ambient temperature; eliminating the need for refrigeration or freezing for food storage; the product can be easily handled and supplied at any time and location. However, the disadvantages of the commercial sterility process include the requirement for expensive steam production; the unsuitability of certain products for this process; the potential destruction of products due to high temperature and pressure process; and the limitation on product size imposed by packaging volume (Pursito et al., 2020).