Effects of multiple freezing (−18 ± 2 °C) and microwave thawing cycles on the quality changes of sea bass (Dicentrarchus labrax)

Abstract

Sensory, chemical [pH, total volatile basic nitrogen (TVB-N), trimethylamine (TMA-N), thiobarbituric acid (TBA)] and composition (crude protein and crude lipid) analyses were carried out on whole, gutted and fillets of seabass that were frozen (−18±2°C) and thawed more than once in microwave. It was detected that the sensorial acceptability values decreased certainly for all fish samples (whole, gutted and fillets of sea bass) when compared with control group. While chemical (pH, TVB-N, TMA-N, TBA) values increased, crude protein and crude lipid values decreased after the multiple freezing and thawing cycles under microwave. The obtained results offered that thawing by microwave is not appropriate sea bass because of the undesirable cooking effect of microwave to the some parts of fish such as tail, eye and fins. Also skin dryness, moisture losses in eye fluids and textural deteriorations were observed. Significant differences (P<0.05) were found in general acceptability values and pH, TVB-N, TBA and crude protein results among the sea bass groups thawed in microwave conditions.

Influence of Freezing–Thawing Cycle on Water Dynamics of Turbot Flesh Assessed by Low-Field Nuclear Magnetic Resonance and Magnetic Resonance Imaging

“…Each thawing process was carried out until the middle point temperature reached up to 4 ± 2 °C using a single-channel optical fiber thermometer (ORW-Y, Orien Inc., Nanjing, China) [21]. The flesh samples were kept in a freezer at −18 ± 2 °C and sealed with plastic wrap until the thawing treatments.…”

“…In order to describe the status and distribution of water during the process in details, multiexponential fitting of the CPMG relaxation data was applied to obtain T 2 relaxation spectra, and three main water populations were identified (Figure 1b). The population with the shortest relaxation time T 21 Figure 1d), with a range of 147.61-321.42 ms, was ascribed to free water, which was in the place of myofibrils (extra-myofibrillar) [18,27]. The LF-NMR relaxation result of Sardine, tuna and mackerel flesh frozen at −40 °C and stored for 1 day (24 h) has also shown three domains from different pools of protons (i. e. low mobile, medium mobile and high mobile) [20].…”

Effects of multiple freeze–thaw cycles on the quality of frozen dough

“…Repeated freezing and thawing is common in both restaurants and retail outlets, and even in domestic kitchens; it can also occur during transport or storage (Srinivasan, Xiong, & Blanchard, 2015). Temperature variation, a core issue in the cold-chain dough business especially in developing countries, is related to physiological and biochemical changes in the quantity of the final food product (Baygar, Alparslan, & C ß Aklı, 2013;Eckardt, € Ohgren, & Alp, 2013;Jia, Huang, & Wu, 2012). Therefore, knowing the changes in cooking and texture characteristics and the water distribution in the dough during repeated freezing and thawing is necessary in order to provide high-value dough products to the customer in a reasonable manner.…”

Effec t of Freeze-Thaw Cycles on Lipid Oxidation and Myowater in Broiler Chickens

“…Especially in restaurants and meat markets, these freeze-thaw cycles may be repeated several times. It is very important to determine the quality changes that occur during multiple freezethawing treatments (Baygar et al, 2012), and therefore, optimum thawing procedures should be of concern of food technologists (Kalichevsky et al, 1995). The most common and widely preferred method of thawing frozen food is placing it in the refrigerator.…”