Superchilled Samples Research Articles

Quantitative analysis perspective: Ice growth and super-chilling state of frozen dough under quick freezing

Ice crystal growth and dough quality under quick freezing were investigated in this study. The ice growth state (content and location) was analysed by the enthalpy balance method and electron microscopy analysis. The superchilling state was judged based on the quantitative analysis of ice crystals. The yeast fermentation performance and dough rheological properties of the frozen dough were assessed. The results showed that the −40 and −80 °C treatments led to quick dough freezing compared with the −20 °C freezing condition. Superchilled dough could be created at −40 °C (less than 35 min) or −80 °C (20 min). The yeast is intolerant to low temperature (−80 °C) based on the results of the dough system and the solution system. Moreover, for dough leavening performance, the freezing temperature and time should be taken into consideration. The elastic modulus and viscous modulus of the dough decreased after the freezing treatment, while the rheological characteristics of the superchilled samples were close to those of the unfrozen samples, which implies that the superchilling treatment maintained the gluten network structure of the dough.

Effects of kojic acid on changes in the microstructure and myofibrillar protein of duck meat during superchilled storage.

This study investigated the effect of 0.8% (m/v) kojic acid treatment on changes in the microstructure and myofibrillar protein of duck meat covered with oxygen-permeable polyvinylchloride (PVC) film (9±0.5µM) during superchilled storage (-1.65±0.5°C). The superchilled samples exhibited wider gaps between muscle fibers at 5 weeks storage compared with kojic acid-treated groups. Based on the variation of water status, the water-holding capacity decreased significantly (p<0.05), and bound water and immobilized water were gradually converted into free water during superchilled storage. For kojic acid-treated samples, however, no major changes were observed with respect to muscle structure, water status, and protein degradation at 6 weeks. The 0.8% (m/v) kojic acid treatment increased the water-holding capacity, reduced carbonyl content and protein degradation, and decreased the α-helix contents loss of myofibrillar proteins. Kojic acid treatment effectively protected myofibrillar protein structure from being destroyed during superchilled storage, suggesting that this method was a good way to reduce protein oxidation and prolonged its shelf life.

Superchilling of poultry meat for improved storage stability

Superchilling, a new concept of extending shelf life of fresh food products without freezing, has been confined mainly to seafoods and scanty work has been documented on poultry meat. Hence, poultry breast fillets were aerobically packaged and stored under superchilling (-2+0.5°C) condition for its storage stability as compared to frozen (-20+1°C) fillets. During storage period of 20 days, there was significant decrease in protein and fat content of both superchilled and frozen samples with an improvement in moisture in superchilled samples. The overall pH was significantly low in superchilled fillets at the end of storage. The water holding capacity of superchilled fillet was significantly higher with lower drip loss whereas extract release volume and water activity decreased duringstorage. The thiobarbituric acid and tyrosine values in both the samples increased significantly from day 10 onwards. The superchilled meat had significantly higher total plate count and psychrophilic count throughout the study. There was significant reduction in Lightness (L*) and yellowness (b*) score as well as significant increase in the redness (Hunter a* value) score of superchilled breast fillet as compared to frozen fillets. The hardness and shear force values were significantly higher in frozen fillets than that of superchilled fillets suggesting the beneficial effect of superchilling in extending the shelf life upto 20 days under aerobic packaging conditions without adverse effect on its quality

Protein degradation and structure changes of beef muscle during superchilled storage

This study investigated the effect of superchilled storage (−4 °C) on protein degradation and structural changes of beef steaks from M. longissimus lumborum compared with traditional chilling (2 °C) and frozen storage (−18 °C). Traditional chilling induced significantly greater degradation of troponin T and desmin, and more rapid loss of calpain activity, compared to superchilled or frozen storage treatments. The proteolysis of key myofibrillar proteins resulted in a sharp decline of WBSF values during traditional chilled storage. For frozen beef samples, no major changes were observed with respect to protein degradation or muscle structure during storage. However, superchilled samples exhibited wider gaps between muscle fibers at 12 weeks storage, associated with muscle fiber shrinkage.

Changes in the Quality of Chicken Breast Meat due to Superchilling and Temperature Fluctuations during Storage.

The aim of this study was to determine the changes in chicken breast meat quality (water-holding capacity, color, texture, myofibrillar fragmentation index (MFI), total protein solubility, thiobarbituric acid reactive substances (TBARS), total viable count (TVC), and lactic acid bacteria (LAB) count) due to storage under superchilling conditions (−1.3°C) and fluctuating temperatures (ranging from −20°C to −5°C) as compared to the quality of meat stored at chilled (2–4°C) and frozen (−20°C) temperatures, respectively. Results indicated that the TVC and LAB count of the chilled and superchilled breast meat increased with storage time. TVC of the chilled and superchilled breast meat reached the safety level of 7 log cfu/g at approximately day 8 and18, respectively. This suggested that the superchilling method extended the storage duration by 10 days. Weight loss and TBARS of the chilled and superchilled samples tended to increase with increasing storage time. The color, texture, protein solubility, and MFI were stable throughout the entire storage period of the chilled (9 days) and superchilled (28 days) samples. Results indicated that while three cycles of storage temperature fluctuation influenced the weight loss and dry matter of the meat, they did not affect the TVC, LAB count, texture, color, pH, MFI, and protein solubility. The superchilling technique (−1.3°C) could extend the shelf-life of meat and maintain the quality of chicken breast meat. Fluctuations in temperature during frozen storage decreased the water-holding capacity of chicken breast meat, indicating that temperature stability should be maintained during frozen storage.

Interrelationship among ferrous myoglobin, lipid and protein oxidations in rabbit meat during refrigerated and superchilled storage

This work investigated the interrelationship among myoglobin, lipid, and protein oxidations in rabbit meat during refrigerated and superchilled storage. Peroxide value gradually increased (p < 0.05) and decreased thereafter (p > 0.05) with increased storage time for both storage treatments. Thiobarbituric acid-reactive substances (TBARS) significantly increased (p < 0.05) throughout the storage time for the storage temperature considered. The metmyoglobin proportion markedly increased (p < 0.05) and remained constant thereafter (p > 0.05). For both storage temperature levels, the extractable heme iron content significantly declined (p < 0.05), whereas non-heme iron content considerably increased (p < 0.05). With prolonged storage time, the protein carbonyl content significantly increased (p < 0.05), along with significant loss in sulfhydryl content (p < 0.05). Superchilled samples maintained lower rates of increase in metmyoglobin content, TBARS, and protein carbonyl content compared with refrigerated samples. Moreover, principal component analysis presented good correlations between TBARS, protein carbonyls and metmyoglobin content. Taken together, myoglobin, lipid and protein oxidations occurred concurrently in rabbit meat during both storage treatments and each oxidation process seemed to promote the other.

English

Biochemical changes of Atlantic salmon (Salmo salar) i¬llets during superchilled storage were evaluated. Due to the signii¬cant differences in ice crystal sizes observed, the biochemical changes were evaluated both at the top and centre parts of the superchilled samples. No signii¬cant differences were found in biochemical changes between top and centre parts of the superchilled samples. The amount of cell tissue fluid (CTF) increased significantly from day 1 to 3 in the top and centre parts of the superchilled samples. The amount of CTF was stable between day 3 and 14 but increased significantly from day 21 to 28. A significant increase in the activity of β-N-acetyl-glucosaminidase in the CTF at the top was observed between day 3 and 7, while at the centre at day 7 of storage. There was also a significant increase in β-N-acetyl-glucosaminidase both at the centre and the surface of the superchilled samples between day 21 and 28 of storage whereby the activity in these samples was on the same level as in the frozen samples. In the superchilled samples, the cathepsin B activity in CTF and homogenates were stable for the first one week of storage. There was significant increase in activity of cathepsin B in cell tissue fluid and homogenates between day 21 and 28 for both chilled and superchilled samples. These i¬ndings provides valuable information on the quality of food products for the food industry in relation to ice crystallisation/recrystallisation during superchilled storage. Key words: Partial freezing, biochemical changes, superchilled storage, salmon fish (Salmo salar).

Effect of Super-Chilling on the Shelf Life of Chicken Nuggets

This study was conducted to assess the composition, physicochemical, microbiological and sensory quality of aerobically packaged&nbsp; chicken nuggets stored at two different superchilling temperature (-2 ±0.5ºC and -0.5±0.5ºC) and compare with storage under frozen&nbsp; (-20±1ºC) and chilling (4±1ºC) temperature for 35 days. The products stored at chilling (4±1ºC) temperature spoiled within 28 days.&nbsp; The moisture content of super-chilled samples was significantly lower than frozen sample and higher than chilled samples. However&nbsp; there was no significant variation in the fat content of the product stored at different temperatures. There was a significant increase in&nbsp; pH of chilled samples than super-chilled with progress in the storage period. The TBA and tyrosine values of the superchilled samples&nbsp; were significantly lower than chilled samples during the storage. Super-chilled nuggets showed significantly lower TPC and psychrophillic&nbsp; counts as compared to chilled nuggets. Sensory evaluation also revealed significantly high scores for super-chilled product than chilled&nbsp; nuggets indicating usefulness of super-chilling temperature for extension of shelf life.&nbsp

Changes of proteins during superchilled storage of Atlantic salmon muscle (Salmo salar).

Changes in protein stability in relation to ice crystals development in salmon fillets during superchilled storage were studied. Due to the significant differences in ice crystal sizes observed in our previous studies, the protein solubility was analysed separately, at the surfaces and centres of the superchilled samples. The water-soluble proteins were stable for the entire storage time. The salt-soluble proteins in the superchilled samples were stable for 1week of storage. The salt-soluble proteins were significantly decreased at day 7 and 14 of the centre and surface of the superchilled samples, respectively. In contrast, the salt-soluble proteins were significantly increased at day 21 both at the centre and surface of the superchilled samples. These findings are significant for the industry because it provides valuable information on the quality of food in relation to ice crystallization/recrystallization during superchilled storage.

Changes in water holding capacity and drip loss of Atlantic salmon (Salmo salar) muscle during superchilled storage

Changes in water holding capacity and drip loss of Atlantic salmon (Salmo salar) fillets during superchilled storage were studied. Due to the significant differences in ice crystal sizes observed in our previous study, the liquid loss (LL) was analysed separately, at the surface and centre of the superchilled samples. No significant differences were found in LL between surface and centre parts of the superchilled samples. No significant difference in the LL was observed from surface samples between 1 and 14 days of storage. There was a significant difference in the LL at day 1 of the centre samples, but no significant differences were observed between 3 and 14 days of storage. In contrast, the LL was significantly decreased at day 21 both at the centre and the surface of the superchilled samples. No significant difference (p<0.05) was found in drip loss between 1 and 14 days of storage for the superchilled samples. A significant increase in drip loss for the superchilled samples was observed at day 21. These findings are significant for the industry because it provides valuable information on the quality of food in relation to ice crystallisation/recrystallisation during superchilled storage.

Ice crystal development in pre-rigor Atlantic salmon fillets during superchilling process and following storage

The objectives of this work were to compare ice crystal sizes of pre-rigor Atlantic salmon fillets subjected to two processes of superchilling and to assess the size changes during storage of superchilled samples at −1.7 ± 0.3 C. The fillets were superchilled in an impingement freezer at either a slow rate (−20 °C, 153 W/m2 K, 4.2 min) which is referred to as process S or a fast rate (−30 °C, 227 W/m2 K, 2.1 min) which is referred to as process F before storage for 29 days. Significantly smaller (p < 0.05) equivalent diameters of ice crystal occurred at faster superchilling rate when compared to slower superchilling rate. The influence of these processes on the microstructure of pre rigor salmon fillets was studied. The equivalent diameter of the intracellular ice crystals formed were 60 ± 5 and 23 ± 1 μm for the samples subjected to processes S and F, respectively. Significant differences were observed between the size of ice crystals formed during the superchilling process and during storage of superchilled samples. The formation of ice crystals within salmon muscle regardless of the superchilling rates was an important factor in reducing cell structure damage.

Quality changes during superchilled storage of pork roast

Quality parameters (sensory, physical, biochemical and microbiological) of superchilled vacuum packed boneless pork roasts were studied during storage for 16 weeks. Superchilling of vacuum packed pork roast at a temperature of −2.0 °C improved shelf life significantly compared to traditional chilled storage at +3.5 °C. Superchilled pork roasts maintained good sensory quality and low microbiological counts during the whole storage period. The drip loss in superchilled samples was lower and showed less variation than in the references and the temperature abused roasts. The consequences of an interrupted cold chain during storage were also investigated. Superchilled samples with temperature abuse resembled chilled samples with respect to drip loss and microbial levels. To take advantage of all the benefits of superchilling and successfully implement the process in the food industry a stable, controlled temperature during storage is critical.