Effects of high pressure and ohmic heating on shell loosening, thermal and structural properties of shrimp (Pandalus borealis)

Abstract

This study aimed at understanding the effects of high pressure (HP) and ohmic heating (OH) on the peelability, the underlying mechanisms of HP-and OH-induced shell tightening, the thermal and structural properties of shrimp parts. HP improved the peelability of shrimp at low pressure level (<350 MPa) and short holding time (≤3 min) and the optimum condition for peeling was at 100 MPa for 3 min at 5°C. However, a higher pressure level (>350 MPa) led to a decrease in the peelability. High pressure at 600 MPa stabilized cuticular and epidermal collagen and formed new collagen-like structures by new linkages, which strengthened the muscle-shell connection and reduced the peelability. Shrimp meat induced from HP at 100 MPa and 600 MPa had minorly denatured myofibrillar proteins. OH as a blanching method did not significantly improve the peelability of shrimp at most of the studied conditions. Some extreme conditions (e.g. at 50°C) caused a markedly low peelability due to occurrence of collagen gelatinization. The gel formation from collagen-gelatin transformation under heating added strength to adherence of shell to epidermis and muscle, as a consequence, a difficult peeling was experienced. OH also denatured proteins in shrimp meat and caused loss of astaxanthin. Industrial relevance: The industrial processing of ready-to-eat shrimp involves the on-ice or in-brine maturation process which loosens the shrimp's shell from its meat, and therefore enable the mechanical peeling. However, the traditional maturation is time consuming (up to 4-5 days), inevitably leads to reduced quality of shrimp meat. This study shows the possibility of the application of HP at mild pressure levels to promote the shell loosening at short HP processing time (≤3 min). However, at more severe HP conditions could lead to the shell tightening which was caused by HP-induced stabilization of collagen in shell and epidermis. The study also shows that ohmic heating (<5 min) might not be a significant blanching method to support the maturation since OH had minor positive effect on shell loosening at 3 some OH conditions (e.g. 2 or 10% NaCl, 92V, and 30 or 35°C), but had a counter effect at most OH conditions especially at high temperature.

Monitoring Thermal and Non-Thermal Treatments during Processing of Muscle Foods: A Comprehensive Review of Recent Technological Advances

“…Fluorescence excitation-emission matrices (EEM), or called fluorescence landscapes in some references, take longer time to collect but enable scanning over a wide range of excitation and emission wavelengths, giving more information about fluorophores present in the sample. The EEM technique was investigated recently to identify changes of fluorescence behavior of shrimp during different treatments, including ohmic heating [54]. One of the spectroscopic results reported in this study was that the tryptophan fluorescence appeared to be highly dependent on the temperature of the treated shrimp samples.…”

“…Ohmic heating was applied as a blanching method prior to maturation. The impact of ohmic heating and high pressure on peelability, thermal and structural properties of shell and meat of shrimp were discussed [54] Pork batters Ohmic heating…”

“…More specifically, Raman spectra can provide useful information about changes taking place in α-helix and β-sheet structures of protein as affected by thermal treatments. Indeed, it has been frequently reported that the content of α-helix decreases, while the content of β-sheet increases with increasing temperature [54,154,157].…”

“…It is well-known that fluorescence from proteins is due to emission from the aromatic amino acids, especially tryptophan. Decreases in fluorescence intensity and red shift of the maximum emission are reported in several studies in the literature to be the result of thermal protein denaturation and tryptophan exposure to increasing solvent polarity [54,177]. Thus, the fluorescence properties of tryptophan have been used to provide information about the extent of thermal treatments and protein denaturation occurring during various processing.…”

A quantitative method to analysis shrimp peelability and its application in the shrimp peeling process

“…While, it is difficult to measure the area of shrimp, Dang et al. (2020) proposed to consider about the relationship between peeling and mass. Regression oblique line as shown in Figure 3 indicated the relationship between peeling work and sample mass.…”