Effects of multiple freeze–thaw cycles on meat quality,nutrients, water distribution and microstructure in bovine rumen smooth muscle

This study investigated the effect of 5 freeze–thaw cycles (freezing at −18°C for 12 h and then thawing at 4°C for approximately 12 h) on the meat quality, proximate composition, water distribution and microstructure of bovine rumen smooth muscle (BSM). As the number of freeze–thaw cycles increased, BSM pH, shear force, water content and protein content decreased by 3.06%, 35.50%, 14.49% and 21.11%, respectively, whereas BSM thawing loss, cooking loss, pressing loss, total aerobic count (TAC), ash content and fat content increased by 108.12%, 47.75%, 78.33%, 90.99%, 105% and 35.20%, respectively. The freeze–thaw cycles resulted in greater protein and lipid oxidation, as evidenced by a 36.46% reduction in the sulfhydryl content and a 209.06% and 338.46% increase in the carbonyl and malondialdehyde contents, respectively. Ice crystal formation disrupted the structural integrity of the muscle tissue. Low-field nuclear magnetic resonance results showed that the freeze–thaw cycles prolonged the relaxation times (T_2b, T₂₁ and T₂₂), indicating that immobile water shifted to free water, and consequently, free water mobility increased. After 3 freeze–thaw cycles, the decline in shear force slowed, the increase in thawing loss became accelerated, and the TAC approached the domain value (6 log colony-forming units/g). Therefore, the number of freeze–thaw cycles of smooth muscle during transport, storage and distribution should be controlled to 3 or fewer. The current results provide a theoretical basis and data support for the further utilisation and culinary processing of smooth muscle.     

Physicochemical and enzymatic changes of cod muscle proteins subjected to different freeze–thaw cycles

The effects of freeze–thaw cycles on the physicochemical and enzymatic changes of cod muscle proteins were investigated. The activities of α‐glucosidase and β‐N‐acetyl‐glucosaminidase increased as the the number of freeze–thaw cycles increased. A loss of Ca²⁺‐ATPase and Mg²⁺‐Ca²⁺‐ATPase activities was observed, while Mg²⁺‐EGTA‐ATPase activity increased, especially after one cycle of freezing–thawing, with a concomitant decrease in Ca²⁺ sensitivity. The surface sulphhydryl group content decreased with increasing freeze–thaw cycles, while no changes in total sulphhydryl group content were found. The surface hydrophobicity of actomyosin did not change significantly with the number of freeze–thaw cycles. The loss of protein solubility increased with increasing freeze–thaw cycles. However, no cross‐linked proteins induced by formaldehyde were found. The results revealed that freeze–thaw cycles directly affected the physicochemical and enzymatic properties of cod muscle proteins. © 2000 Society of Chemical Industry     

Stability of anthocyanins in frozen and freeze-dried raspberries during long-term storage: in relation to glass transition

Abstract: Anthocyanins, natural plant pigments in the flavonoid group, are responsible for the red color and some of the nutraceutical benefits of raspberries. This study explores anthocyanin degradation in frozen and freeze‐dried raspberries during storage in relation to glass transition temperatures. Frozen raspberries were stored at ?80, ?35, and ?20 °C, while freeze‐dried raspberries were stored at selected water activity (a_w) values ranging from 0.05 to 0.75 at room temperature (23 °C) for more than a year. The characteristic glass transition temperatures (T′_g) of raspberries with high water content and glass transition temperature (T_g) of raspberries with small water content were determined using a differential scanning calorimeter. The pH differential method was used to determine the quantity of anthocyanins in frozen and freeze‐dried raspberries at selected time intervals. The total anthocyanins in raspberries fluctuated during 378 d of storage at ?20 and ?35, and ?80 °C. Anthocyanin degradation in freeze‐dried raspberries ranged from 27% to 32% and 78% to 89% at a_w values of 0.05 to 0.07 and 0.11 to 0.43, respectively, after 1 y. Anthocyanins were not detectable in freeze‐dried raspberries stored at a_w values of 0.53 to 0.75 after 270 d. First order and Weibull equations were used to fit the anthocyanin degradation in freeze‐dried raspberries. The 1^st‐order rate constant (k) of anthocyanin degradation ranged from 0.003 to 0.023 days^?1 at the selected water activities. Significant anthocyanin degradation occurred in both the glassy and rubbery states of freeze‐dried raspberries during long‐term storage. However, the rate of anthocyanin degradation in freeze‐dried raspberries stored in the glassy state was significantly smaller than the rate of anthocyanin degradation in the rubbery state.     

Characterization of the recombinant succinic semi‐aldehyde dehydrogenase from Saccharomyces cerevisiae

The yeast succinic semi‐aldehyde dehydrogenase gene (SSADH; EC 1.2.1.16) was cloned and overexpressed in Escherichia coli. Based on SDS–PAGE, the molecular mass of the subunit was around 54 kDa, and the purified recombinant enzyme had a tetrameric molecular mass of ca. 200 kDa. The specific activity of the recombinant enzyme was 1.90 µm NADH formed/min/mg, and showed maximal activity at pH 8.4. The recombinant protein was highly specific for succinate semi‐aldehyde (K_m = 15.48 ± 0.14 µm ) and could use both NAD⁺ and NADP⁺ as co‐factors, with K_m values of 579.06 ± 30.1 µm and 1.017 ± 0.46 mm, respectively. Initial velocity studies showed that NADH was a competitive inhibitor with respect to NAD⁺ (K_i = 129.5 µm ) but a non‐competitive inhibitor with respect to succinate semi‐aldehyde. Adenine nucleotides of AMP, ADP and ATP inhibited yeast SSADH activity with K_i = 1.13–10.2 mm, and showed competitive inhibition with respect to NAD⁺ and mixed‐competitive, non‐competitive and non‐competitive inhibition, respectively, with respect to succinate semi‐aldehyde. The kinetic data suggest a 'ping‐pong' mechanism. Copyright © 2014 John Wiley & Sons, Ltd.     

Formation and stability of emulsions stabilised by Yucca saponin extract

Yucca saponin extract containing steroidal saponins was examined for its interfacial and emulsifying properties. For this purpose, we produced oil‐in‐water emulsions and tested their stability against environmental stresses (pH, ionic strength, heating and freeze‐thawing). Yucca saponin extract was highly surface‐active and formed negatively charged submicron‐sized emulsions at low surfactant‐to‐oil ratio. The emulsions were stable at pH 5–9 and showed only minor increase in droplet size when heated up to 90 °C. Our results indicate Yucca saponin extract as a new potential natural surfactant that may be used to replace synthetic surfactants in the food and beverage industry for selected applications.     

Comparison of the Cryoprotective Effects of Trehalose,Alginate, and Its Oligosaccharides on Peeled Shrimp (Litopenaeus Vannamei) During Frozen Storage

The cryoprotective effects of trehalose, alginate, and its oligosaccharides on peeled shrimp (Litopenaeus vannamei) during frozen storage was investigated by monitoring thawing loss, color, texture, myofibrillar protein content, Ca²⁺‐ATPase activity, and performing microscopic structural analysis. Data revealed significant (p < 0.05) inhibitory effects on thawing loss and textural variables (springiness and chewiness) in trehalose‐, alginate oligosaccharides‐, and sodium pyrophosphate‐treated shrimp compared with the control and alginate‐treated batches. L* values revealed that these saccharides had a positive effect on color stability during frozen storage. In addition, the results of chemical analyses showed that trehalose and alginate oligosaccharide treatments effectively maintained an increased myofibrillar protein content and Ca²⁺‐ATPase activity in frozen shrimp. In addition, hematoxylin & eosin staining and SDS‐PAGE confirmed that these cryoprotective saccharides slowed the degradation of muscle proteins and the damage to muscle tissue structures. Overall, the application of trehalose and alginate oligosaccharides to peeled frozen shrimp might maintain better quality and extend the commercialization of these refrigerated products.     

Non-destructive Visible/NIR Spectroscopy for Differentiation of Fresh and Frozen-thawed Fish

Nondestructive visible/near‐infrared (NIR) spectroscopy was evaluated to investigate whether fish has been frozen‐thawed. Fresh or frozen‐thawed red sea bream Pagrus major (n= 108) were scanned using a NIRSystems 6500 spectrophotometer equipped with a surface interactance fiber‐optic accessory then discriminated by soft independent modeling of class analogy (SIMCA) and linear discriminant analysis (LDA) based on principal component analysis (PCA) scores. The major effect of freeze‐thawing treatment involves a gross change in total reflectance after freezing and thawing; this arises from changes in light scatter presumably arising from alterations in the physical structure of at least the surface layer of fish. Untreated original absorbance spectra achieved much better (100%) classification accuracy for the prediction samples while the same figures for multiplicative scatter correction (MSC) treated spectra are considerably worse, indicating that scattering is the major information that makes classification work. No incorrect type of classification at all and also there are no samples classified to both groups either. This faster technique has the potential to differentiate fresh and frozen‐thawed fish and could be applied for online or at‐line processing control.     

Insolubilisation and gelation of heat–frozen soymilk

Soymilk prepared from soybean seed was heated and frozen. After thawing, precipitation was shown to occur in soymilk. Precipitation from heated and frozen soymilk increased with increase in heating time. Precooling treatment (−5°C) before freeze‐storage of heated soymilk resulted in gel‐like solidification of soymilk. The gel strength of the freeze‐gel formed from soymilk was related to the heating time and the viscosity of the soymilk before freezing. © 1999 Society of Chemical Industry     

Kinetics of fructose on the Maillard brown colour development,pH change and antioxidative activity development in model fructose/glycine systems

Model fructose/glycine systems with fructose concentration between 0.035 and 0.28 m were incubated at temperature 45–90 °C for investigating the effects of fructose and temperature on the brown colour development, pH change and the antioxidative activity developments of Maillard reaction. The result showed that effects of fructose followed logarithm‐order kinetics on brown colour and DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) radical scavenging activity (S_DPPH) development, and first‐order kinetics on system pH decrease. However, the effect of fructose on ABTS·⁺ (2,2′‐azino‐bis[3‐ethylbenzthiazoline‐6‐sulphonic acid]) radical scavenging activity (S_ABTS) development was first order at 60–90 °C and logarithm order at 45 °C, which revealed the mutual synergistic interaction of concentration with temperature on S_ABTS development. Activation energy for S_DPPH development was lower than that for S_ABTS development, revealing that DPPH radical was more vulnerable than ABTS·⁺ radical to fructose/glycine MRPs at low temperature. But the relative vulnerability would invert at high temperature, as the Q₁₀ value for S_DPPH development was lower than that for S_ABTS development.     

PHYSICOCHEMICAL PROPERTIES OF MUSCLE AND NATURAL ACTOMYOSIN EXTRACTED FROM FARMED ATLANTIC SALMON (SALMO SALAR) STORED AT 4C

Properties of farmed Atlantic salmon (Salmo salar) obtained commercially were studied as a function of storage at 4C for 9 days. While pH increased gradually during storage for both samples, significant differences between samples were noted in water‐binding capacity (WBC) of muscle, as well as surface hydrophobicity (S_o) and sulfhydryl contents of extracted natural actomyosin (NAM). Lower S_owas observed for NAM extracted from muscle stored for 2 days, coinciding with high WBC of the muscle. In contrast, higher S_ofrom 5 to 7 day‐stored samples coincided with minimum extractability and high apparent viscosity of NAM. Reactive sulfhydryl groups were higher at the beginning and end of storage. Generally, WBC of fish muscle was dependent on pH and related to changes in S_oof NAM, while apparent viscosity increased with S_oand disulfide content. The results indicate variability in functional properties of the salmon samples during cold storage, which could be attributed to changes in physicochemical properties of NAM.     

Lipoamide dehydrogenase, citrate synthase and beta-hydroxyacyl-CoA-dehydrogenase of skeletal muscle. 9. Influence of frozen storage of musculature of sheep, game and poultry on activity and subcellular distribution

Frozen storage at -20 degrees C for three months and thawing of muscles from sheep, hare and deer, and of the breast and leg muscles from chicken and duck did not result in significant changes in the extractable total activities of the mitochondrial enzymes citrate synthase and beta-hydroxyacyl-CoA-dehydrogenase; however there was a decrease in the total activity of lipoamide dehydrogenase except in the chicken leg muscle, where such a decrease did not occur. From the increase in the activities of the three enzymes in the muscle press juice it was concluded that - additionally to the effect of freezing and thawing itself - frozen storage results in further damage to the inner membrane of muscle mitochondria which is signalled by the release of membrane-bound enzymes. Chicken muscle mitochondria seem to be more stable against frozen storage of the tissue than the mitochondria in the muscles of the other species studied (including bovine and porcine muscle).     

Freezing, thawing and cooking effects on quality profile assessment of green beans (cv. Win)

Results are presented of the effect of freezing followed by thawing (air and water immersion, both at environmental temperature) and cooking (traditional boiling in a covered pot) on quality profile (in terms of objective texture, colour, chlorophylls and pheophytins and sensory attributes) and structure of green beans (cv. Win). Freezing was carried out at three different rates by forced convection with liquid nitrogen vapour. Kramer shear cell (KSC) and Warner–Bratzler (WB) tests were used for objective assessment of the texture. The highest parameter values occurred in beans frozen at the highest rate and air-thawed at the slowest rate. Also, minimum alteration of the rheological behaviour of cooked beans was achieved by freezing at the highest rate. The best parameter for assessing the texture of frozen green beans after thawing and cooking was the Warner–Bratzler slope (S _WB). Coefficients of softening estimated for S _WB in the thawed beans showed that the texture of the beans frozen at −24 °C was almost four and almost five times softer than that of the beans frozen at −70 °C, for air and water thawing respectively. Frozen and thawed green beans were darker than fresh control, whereas freezing prior to cooking produced lighter-coloured beans than direct cooking. The freezing rate affected colour parameters differently depending on the process that followed. When beans were thawed, increasing the freezing rate produced lighter-coloured beans, whereas when beans were cooked, increasing the rate produced darker-coloured beans. No difference was found in sensory assessments between cooked samples frozen at −24 °C, −35 °C and −70 °C, which probably reflects the panellists' mixed preferences for quickly and slowly frozen samples. Scanning electron microscopy (SEM) revealed different degrees of mechanical damage to tissue structure, which accounted for the rheological behaviour of the beans.     

Fermentation Process and Grain Structure of Baked Breads from Frozen Dough Using Freeze-Tolerant Yeasts

The fermentation process for frozen doughs using freeze‐sensitive (Saccharomyces cerevisiae, Kyowa for sweet bread; S. cerevisiae, FC for white bread) and freeze‐tolerant (S. cerevisiae, YF for sweet bread) yeasts was traced by magnetic resonance imaging (MRI). Grain network structures of baked breads were also visualized by MRI. Prefermentation before freezing, punching and remolding, or resheeting and molding treatments increased loaf volume by 10 to 110% for the baked breads using freeze‐tolerant yeast, while these treatments decreased loaf volume by 70% using freeze‐sensitive yeast. The first fermentation before freezing and the second fermentation with punching or resheeting after thawing are useful for obtaining good quality breads from frozen dough using freeze‐tolerant yeast.     

Freezing of meat and aquatic food: Underlying mechanisms and implications on protein oxidation

Over the recent decades,protein oxidation in muscle foods has gained increasing research interests as it is known that protein oxidation can affect eating quality and nutritional value of meat and aquatic products. Protein oxidation occurs during freezing/thawing and frozen storage of muscle foods, leading to irreversible physicochemical changes and impaired quality traits. Controlling oxidative damage to muscle foods during such technological processes requires a deeper understanding of the mechanisms of freezing-induced protein oxidation. This review focus on key physicochemical factors in freezing/thawing and frozen storage of muscle foods, such as formation of ice crystals, freeze concentrating and macromolecular crowding effect, instability of proteins at the ice–water interface, freezer burn, lipid oxidation, and so on. Possible relationships between these physicochemical factors and protein oxidation are thoroughly discussed. In addition, the occurrence of protein oxidation, the impact on eating quality and nutrition, and controlling methods are also briefly reviewed. This review will shed light on the complicated mechanism of protein oxidation in frozen muscle foods.     

Influence of Freezing and Thawing on the Release of Cytochrome Oxidase from Chicken's Liver and from Beef and Trout Muscle

The process of freezing and thawing animal tissues causes a remarkable release of cytochrome oxidase from mitochondria. The activity of cytochrome oxidase in extracts of tissues after freezing and thawing increases by 15 times in chicken's liver, by 2.5 times in trout, and by 4 times in beef muscle, as compared to extracts of unfrozen samples. These results suggest that the measurement of cytochrome oxidase activity can be used to develop a rapid and simple method which could allow distinguishing between unfrozen and frozen and thawed tissues.     

Comparative studies of the mitochondrial properties of longissimus dorsi muscles of pietrain and large white pigs

Investigations, using various techniques (electron microscopy, polarography, spectrophotometry), on mitochondria isolated immediately post-mortem from the Longissimus dorsi (LD) muscles of stress-susceptible (SS) Pietrain and stressresistant (SR) Large White pigs suggest no marked biochemical difference in their mitochondrial properties. There was no evidence of “uncoupling” ² nor of aberrant mitochondrial energy metabolism”³ in the mitochondria of either breed of pig. The difference observed between the two breeds in mitochondrial cytochrome c content, in the State 3 rate of oxidation of succinate and of ascorbate plus tetramethyl-p-phenylenediamine (TMPD) and in the maximum time of mitochondrial storage in situ, could be attributed mainly to differences in initial muscle pH values and in the subsequent rates of pH decline post-mortem. With both breeds of pig intact mitochondria could still be isolated from LD muscle even after prolonged storage as long as the ultimate tissue pH was not below 5.5. Prolonged storage of mitochondria in situ caused a loss of mitochondrial cytochrome c, which was responsible for a decline in the State 3 respiration. The latter could be restored by addition of cytochrome c and ADP. The cytochrome oxidase activity (e.c. 1.9.3.1) was the most stable to post-mortem ageing both in situ (1 °C) and in vitro (0 °C), and the NAD⁺-linked oxidation of pyruvate plus malate, the least stable. The small observed differences in immediate post-mortem mitochondrial function between SR and markedly SS pigs cannot possibly account for the very large differences in post-mortem biochemical behaviour and particularly not for the low initial pH and high rate of post-mortem pH fall, characteristic of SS pigs showing the pale, soft and exudative (PSE) condition.     

Effects of freezing and thawing methods and storage time on thermal properties of freshwater prawns (Macrobrachium rosenbergii)

Thermal stability of proteins in frozen and thawed freshwater prawns was measured by differential scanning calorimetry. The onset and peak melting temperatures corresponding to myosin denaturation, as well as total enthalpy of denaturation of prawn muscle, decreased after freezing–thawing treatments. There were no significant differences in the thermal properties of prawns with changes in the rate of freezing, ie blast (fast) vs still (slow) freezing. However, the thermal properties were influenced by the rate of thawing. Rapid thawing using a combination of microwave and tap water resulted in a lower (P⩽0·05) thermal stability of prawn proteins compared to slow (refrigeration) or moderately fast (tap water) thawing methods. Keeping prawn shells intact or not intact during freezing–thawing did not alter the thermal properties of the prawn proteins. © 1997 SCI.     

Porosity and Water Activity Effects on Stability of Crystalline β‐Carotene in Freeze‐Dried Solids

Abstract: Stability of entrapped crystalline β‐carotene as affected by water activity, solids microstructure, and composition of freeze‐dried systems was investigated. Aliquots (1000 mm³, 20% w/w solids) of solutions of maltodextrins of various dextrose equivalents (M040: DE6, M100: DE11, and M250: DE25.5), M100‐sugars (1:1 glucose, fructose and sucrose), and agar for gelation with dispersed β‐carotene were frozen at ?20, ?40, or ?80 °C and freeze‐dried. Glass transition and α‐relaxation temperatures were determined with differential scanning calorimetry and dynamic mechanical analysis, respectively. β‐Carotene contents were monitored spectrophotometrically. In the glassy solids, pore microstructure had a major effect on β‐carotene stability. Small pores with thin walls and large surface area allowed β‐carotene exposure to oxygen which led to a higher loss, whereas structural collapse enhanced stability of β‐carotene by decreasing exposure to oxygen. As water plasticized matrices, an increase in molecular mobility in the matrix enhanced β‐carotene degradation. Stability of dispersed β‐carotene was highest at around 0.2 a_w, but decreasing structural relaxation times above the glass transition correlated well with the rate of β‐carotene degradation at higher a_w. Microstructure, a_w, and component mobility are important factors in the control of stability of β‐carotene in freeze‐dried solids Practical Application: β‐Carotene expresses various nutritional benefits; however, it is sensitive to oxygen and the degradation contributes to loss of nutritional values as well as product color. To increase stability of β‐carotene in freeze‐dried foods, the amount of oxygen penetration need to be limited. The modification of freeze‐dried food structures, for example, porosity and structural collapse, components, and humidity effectively enhance the stability of dispersed β‐carotene in freeze‐dried solids.     

Studies on isolation and respiratory activity of the mitochondria of Sitophilus granarius (L.)

Mitochondria isolated from Sitophilus granarius by gentle crushing and differential centrifugation appeared in electron micrographs, to have normal morphological features of mitochondria reported from other sources. They resembled mouse-liver mitochondria in their ability to oxidize succinate, pyruvate plus malate and in their response to 2–4-dinitrophenol. They were also able to oxidize pyruvate and α-glycerophosphate similar to mitochondria from other insects and they showed no response to Ca²⁺. The respiratory activity of the weevil mitochondria was inhibited by cyanide, antimycin A and rotenone but stimulated by ADP and DNP similar to mammalian mitochondria.     

Chemo‐enzymatic synthesis of α‐terpineol thioacetate and thiol derivatives and their use as flavouring compounds

Reaction of (R,S)‐α‐terpineol with thioacetic acid in food‐grade n‐hexane resulted into two α‐terpineol thioacetate derivatives with the same molecular weight. After 5 h of reaction time, (R,S)‐α‐terpineol was completely transformed and the mixture analysed by different chromatographic techniques. The aroma character of the α‐terpineol thioacetates was described as exotic, sweet, blackcurrant, roasted and sulphury. Of eight lipases and two esterases assayed, only non‐immobilized pig liver esterase (PLE) hydrolysed α‐terpineol thioacetates into the corresponding α‐terpineol thiols. When reactions were performed in 0.2 m phosphate buffer at pH 8.0 and 30 °C with non‐immobilized PLE, α‐terpineol thiols were produced in an optimal yield of 88% after 24 h of reaction time. The aroma character of α‐terpineol thiols was described as green, exotic and fresh grapefruit. Flavouring powders were prepared by freeze‐drying the α‐terpineol thioacetates and α‐terpineol thiols in the presence of maltodextrine. Preliminary applications showed that these flavouring preparations could be used to improve the flavour quality of lighter cooked notes and tropical fruit aromas. Copyright © 2014 John Wiley & Sons, Ltd.