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This study investigated the utilization of liquid smoke as a natural preservative in fish balls without reducing their nutrition and aesthetic value. The liquid smoke used in this research was obtained through pyrolysis of palm kernel shells at temperatures of 340, 360, and 380°C. The resulting liquid smoke was then purified using a two-stage distillation process at a temperature of 200°C in order to remove unwanted compounds. This grade-1 liquid smoke was then used to preserve fish balls. The parameters assessed to monitor the fish balls' preservation were total volatile bases (TVB), pH, and organoleptic test results. The results showed that the smallest TVB value of 12.66 mgN/100 g at 20 hours was obtained for fish balls preserved using liquid smoke pyrolysis at 380°C (3% concentration). The organoleptic test showed that 90% of respondents preferred the taste, aroma, and texture of the fish balls preserved using liquid smoke pyrolysis at a temperature of 340°C (2% concentration). The pH test showed that the fish balls preserved using liquid smoke possessed a pH above 6, meaning that they were in good condition.

The reaction path and the mechanism of hydrothermal decomposition of glycylglycine (Gly-Gly) and some other dipeptides in the absence of any catalysts were investigated. Experiments were conducted at the temperature range of 240-300 °C and a reaction time up to 200 s. An interesting reaction phenomenon relating to the production of amino acids from hydrolysis of proteins in high-temperature water was observed. Other than hydrolysis of Gly-Gly to produce glycine (Gly), cyclodehydration also took place, producing cyclo(Gly-Gly). The product of Gly from cyclo(Gly-Gly) was also verified. The same reactions were also observed in the case of other dipeptides such as glycylleucine, glycylalanine, and glycylserine. The reaction pathway of the hydrothermal reaction of dipeptides was speculated based on the experimental results to consist of consecutive reversible reactions involving cyclodipeptides, linear dipeptides, and amino acids.

Oil palm kernel shell is a waste product of palm oil manufacturing and contains significant amounts of several chemical compounds including cellulose, hemicelluloses, and lignin. Pyrolysis of these compounds results in good quality liquid smoke. The aim of this research was to utilize this liquid smoke to preserve mackerel. The liquid smoke in this research was obtained by pyrolyzing oil palm kernel shell at temperatures ranging from 300-380°C. The resulting liquid smoke was then distilled at 200°C, and its chemical composition was analyzed using gas chromatography-mass spectrometry. The liquid smoke was then used to preserve mackerel at a variety of concentrations, including 0.5%, 1%, 2%, and 3%. The efficacy of preserving the mackerel using liquid smoke was assessed through TVB (total volatile base) analysis and organoleptic testing. TVB testing showed that mackerel remained fresh for up to 64 hours after being treated with 2% and 3% liquid smoke at a pyrolysis temperature of 380°C, with TVB values of 26.733 mgN and 24.974 mgN, respectively. The organoleptic testing showed that at a liquid smoke concentration of 3% and a pyrolysis temperature of 380°C, mackerel can remain fresh for up to 48 hours, with acceptable color and texture, and is suitable for consumption. Meanwhile, the non-preserved (control) mackerel had already deteriorated within 24 hours in terms of color, texture, and smell.

The purpose of this study was to determine the effectiveness of edible coatings of chitosan dissolved with liquid smoke in preserving meatballs. The liquid smoke was derived from rice hulls pyrolyzed at 340 °C. The edible coating was made by dissolving 0.5%, 1%, and 1.5% chitosan in 100 ml of liquid smoke at concentrations of 3% and 5%. Preservation was carried out by soaking the meatballs in the edible coating solution for 15 min and storing them at room temperature with observations every 6 h. Food resistance was examined using the Antibacterial Activity Test, Total Plate Count (TPC), and Total Volatile Base Nitrogen (TVB-N). The results of the antibacterial activity test showed that chitosan-dissolved liquid smoke had inhibition zones ranging from 6.49–7.07 mm against E. coli and 6.52–7.26 mm against Salmonella bacteria. The use of 5% concentrated liquid smoke reduced the number of bacterial colonies, with TPC values not below the SNI threshold after 48-hour storage. This indicates that liquid smoke has potential as an antibacterial. The TVB-N value doubled after 24 h, but the meatballs still had good freshness. After 54 h of storage time, the TVB-N value in all treatments exceeded the SNI threshold of 0.254 mgN/100 g, and the meatballs were no longer suitable for consumption.