Sakamon Devahastin

Physicochemical, Microstructural, and Microbiological Properties of Skipjack Tuna (Katsuwonus pelamis) After High-Pressure Processing: Properties of skipjack tuna after HPP…

Properties of skipjack tuna loins subjected to high-pressure processing (HPP) at 150 to 600 MPa for 1 to 5 min were compared with those of loin that underwent steam cooking for 10 min. Protein denaturation in HPP-treated loins increased with increasing pressure level, but these loins retained between 1.1% and 2.4% more water than steam-cooked loin. Water holding capacity decreased from 57% to 44% when the loins were treated at 600 MPa. ΔE value of HPP loins was between 5.8 and 26.3 when treated at 150 to 600 MPa, whereas it was 34.1 for steam-cooked sample. Hardness of HPP loins increased from 648 to 1,019, 1,918, 5,249, and 4,092 g and springiness changed from 85.2% to 79.7%, 78.2%, 91.7%, and 90.7%, respectively, when treated at 150, 300, 450, and 600 MPa. Protein fibers of HPP loins had a more irregular shape than those of steam-treated loin. Histamine levels of HPP-treated loins were in the range of 3.08 to 3.35 μg/g, identical to that of steam-treated loin. Thiobarbituric acid assay demonstrated that the level of lipid oxidation increment in HPP-treated loins was twice as high as that in steam-cooked one. Undesirable volatile compound contents in tuna loins decreased with increasing degree of protein denaturation. Steam cooking and HPP at 150, 300, 450, and 600 MPa decreased the total aerobic counts by 4.75, 0.12, 1.20, 4.69, and 6.08 log CFU/g, respectively. These results suggest that HPP at 450 MPa and above has the potential to be used as an alternative to the tuna precooking process.nnnPRACTICAL APPLICATIONnInformation presented here can serve as a guideline for the selection of appropriate conditions for HPP of tuna loins. Our results show that HPP has a potential to replace the highly energy-intensive steam precooking step, which is traditionally required in a canned tuna production process.

EXPERIMENTAL INVESTIGATION OF TWO-STAGE SUPERHEATED STEAM AND HEAT PUMP DRYING OF SHRIMP

The present work proposed the two-stage drying technique concerning on the drying of shrimp using superheated steam dryer followed by heat pump dryer (SSD/HPD) at different drying conditions. The effects of drying temperatures and intermediate moisture contents (IMC) on drying characteristics and dried product quality were investigated. Shrinkage, color and texture of dried shrimp were determined. The experiments were carried out in the two stages of SSD/HPD. The first-stage superheated steam drying was performed at the drying temperatures of 160C and 180C while the second-stage heat pump drying was operated at 50C. The moisture content of shrimp at the end of the superheated steam drying stage (IMC) was varied between 30% and 40% (w.b.). For the comparison, purely SSD (superheated steam drying for the whole drying process) was also performed at the same drying steam temperature as used in the first-stage SSD. As for the effects of drying conditions, the results showed that higher drying steam temperature and higher IMC yielded better product quality only in terms of color. In addition, it was found that SSD/HPD dried shrimp had much lower degree of shrinkage, better color, softer and less tough than purely SSD dried shrimp.