High pressure‐assisted vacuum‐freeze drying: A novel, efficient way to accelerate moisture migration in shrimp processing

Abstract

High pressure processing (HPP), as nonthermal processing technology, has the potential to increase the drying rate due to its improvement of heat and mass exchange in different processes. In this study, the moisture migration in shrimps during HPP‐vacuum‐freeze drying (HPP‐VFD) processes has been monitored by using low‐field nuclear magnetic resonance and magnetic resonance image (MRI) in comparison with hot air‐drying and VFD. Based on the T2 relaxation spectra, three water fractions corresponding to bound water (hydrogen‐bonded water), immobile water (water trapped by organization structure or cell member), and free water were observed. For group B, with increasing drying time (4 to 22 hr), the transverse relaxation times of T21, T22, and T23 were significantly decreased (76.79%, 57.78%, and 40.9%) (P < 0.05). The content of immobile water (A22) and free water (A23) decreased (81.55% and 89.07%), whereas the bound water (A21) increased (7.26%). In comparison with group B, the T21, T22, and T23 of group C showed greater decrease (83.12%, 87.12%, and 89.57% for group C) so that HPP pretreatment could shorten the relaxation time. MRI analysis further proved that HPP‐VFD drying has improved drying efficiency, and moisture migration was from the exterior to the interior part with increasing drying time. SEM analysis demonstrated that no significant damage of muscle fibers with narrower gaps was observed for groups B and C. Overall, HPP, as a pretreatment technology, could accelerate the moisture migration and improve the drying efficiency of VFD process for shrimp. Practical Application High pressure processing (HPP) is now well known as a nonthermal processing technology and becoming increasingly acknowledged. However, there is limited information about its application in shrimp‐drying process and the moisture dynamic of shrimp subjected to high pressure processing‐assisted vacuum‐freeze drying. This study could provide valuable information regarding the moisture status and migration in HPP‐VFD shrimp monitored by LF‐NMR and MRI methods. The results showed that HPP processing at 550 MPa for 10 min can be used as an interesting method for drying pretreatment, increasing its drying rate and consequently reducing its process time, and it demonstrated that the methods used in this study had good correlation coefficient with physicochemical properties of shrimp, which may be real‐time and nondestructive monitoring methods for shrimp‐drying process.

The low‐field NMR studies the change in cellular water in tilapia fillet tissue during different drying conditions

“…The effect of different drying methods on the migration of entrapped water in tilapia fillets ((a) the peak area of the entrapped water; b: the ratio of the entrapped water to the total peak area; (a) UAPOHPD; (b) UAPOVFHPCD) to 44.5℃ at 7 hr of drying from Figure 7a, and the entire sample temperature from surface to the temperature inside the sample reached about 45°C. There is a peak at this temperature, and it might be due to the entire muscle fiber network of the tilapia fillets tend to shrink and break, which increases the content of the free water (Ling et al, 2020); therefore, it can be assumed that the peak of the free water curves is represented as cell membrane collapse point. However, when the drying time was greater than 7 hr, the center temperature and surface temperature of the samples were the same, and the remaining free water in the samples continuously diffused into the drying medium, resulting in a decreasing trend.…”

High‐pressure processing of fish and shellfish products: Safety, quality, and research prospects

“…Levels of TBARS in HPP samples were greatly increased (up to 0.93 ± 0.09 mg MDA/kg at 400 MPa for 10 min) which was caused by the formation of hydroperoxides during HPP treatment. traditional thermal methods are available for microbiological inactivation, HPP is a time-saving and energy-efficient preservation technique for the seafood industry for opening shellfish or crustaceans (Ling et al, 2020). Using HPP , the bivalve shells opened with ease and allowed efficient meat extraction without affecting the product while avoiding cooking.…”

Recent Trends in Pretreatment of Food before Freeze-Drying

“…The authors also noted the strong anti-inflammatory effect of freeze-dried ginseng when the combination of UVT and HHP was used. A previous study [73] used HHP for shrimp pretreatment before FD. The authors of the study observed that HHP improved drying efficiency and moisture migration from the exterior to the interior part of shrimp.…”