Bacterial and Autolytic Changes in Water Retention and Adenosine Nucleotides of Cod Mince

Water uptake ability (WUA), expressible moisture (EM), hypoxanthine (Hx), and inosine (HxR) were monitored in cod mince stored at 0, ?2, ?3°C, with or without bacterial inactivation using NaOCl. Hx and HxR increased (p < 0.05) in all samples during the first 9-10 days. Bacterial inactivation reduced Hx and HxR build up. Beyond day 10, Hx and HxR decreased in all samples. The decrease was slower in samples in which bacterial had been inactivated. Bacterial inactivation deterred WUA increases and EM decrease.     

Water Uptake, Protein Solubility, and Protein Changes of Cod Mince Stored on Ice as Affected by Polyphosphates

Water uptake ability (WUA) and protein solubility of cod mince were higher with sodium hexametaphosphate (SHMP) than with sodium tripolyphosphate (STP) or untreated controls during ice storage. WUA increased significantly with SHMP concentration up to 0.7% SHMP but above that WUA decreased, although protein solubility continued to increase. The SDS-PAGE results showed that extraction of a specific amount of water-soluble protein, perhaps including some myosin heavy chain (MHC, 200 kd), correlated with high WUA. However, excess extraction of MHC may cause destruction of the structural matrix of the insoluble protein network, preventing it from holding water.     

THERMAL AND DYNAMIC-MECHANICAL PROPERTIES OF FROZEN WHEAT DOUGHS WITH ADDED SUCROSE,NaCl, ASCORBIC ACID,AND THEIR MIXTURES

The effects of sucrose, NaCl, and ascorbic acid on the physical state of wheat dough at sub-zero temperatures were investigated using Differential Scanning Calorimetry (DSC) and Dynamic-Mechanical Analysis (DMA). The DSC thermograms were obtained for annealed samples by scanning from ?80 to 10°C at 5°C/min. Added sucrose and NaCl decreased the onset of ice melting of doughs, and they were found at ?26°C. Added sucrose and NaCl increased the relative amount of unfrozen water in doughs, while added ascorbic acid had not noticeable effects. DMA measurements were made for annealed samples at a heating rate of 1°C/min from ?150 to 10°C. The loss modulus, G″, of DMA showed an α-relaxation (glass transition), two low temperature relaxations (β and γ), and melting of ice in all doughs with added ingredients.     

Quality deterioration in frozen Nile perch (Lates niloticus) stored at −13 and −27°C

Nile perch fillets stored at −13 and −27°C were monitored to determine changes in protein functionality [expressible moisture (EM), water uptake ability (WUA), soluble protein (SP) and emulsion capacity (EC)], changes in lipids [free fatty acids (FFA) and malonaldehyde accumulation] and changes in sensory properties. For samples stored at both temperatures, WUA, EC and SP decreased with time of storage while EM, FFA, malonaldehyde and off-flavors increased. Texture, taste and overall acceptability changed only for the samples stored at −13°.     

Glass Transition of Rainbow Trout and Its Oxidation Stability During Storage

Glass transition of rainbow trout muscle was measured by differential scanning calorimetry (DSC) as ?13°C. Sucrose and sorbitol (2, 2), sucrose and mannitol (2, 2), sucrose and gum arabic (2, 0.15), sucrose and carrageenan (2, 0.15), sorbitol and mannitol (2, 2), sorbitol and gum arabic (2, 0.15), sorbitol and carrageenan (2, 0.15), mannitol and gum arabic (2, 0.15) and mannitol and carrageenan (2, 0.15) were blended with ground rainbow trout as g/100 g fish and stored for 6 months separately at ?9°C, ?13°C and ?18°C. Total volatile basic nitrogen (TVB-N) and Thiobarbituric acid-reactive substances (TBARS) were determined at 1^st, 3^rd and 6^th months of storage periods. Biopolymers blends, storage temperature and storage period had a significant effect (p < 0.05) on the TVB-N and TBARS values.     

Processing and Frozen Storage Effects on the Iron Content of Cod and Mackerel

Processing and subsequent frozen storage affected the iron content of cod (Gadus morhua) and mackerel (Scomber scombrus) muscle tissue. Frame mince was obtained from the bone rack, without the head or viscera remaining, after filleting. Frame mince had significantly higher iron levels than intact fillets with or without skin or fillets that were subsequently minced. Skin-on fillets had more iron than skin-off fillets. Cod frame mince had about 50% heme iron, while mackerel frame mince ranged from 20-64%. Nonheme iron increased during frozen storage due to heme breakdown. Storage above ?14°C was more deleterious to the heme molecule than lower temperatures (?20°C or ?40°C).     

Determining Washing Conditions During the Preparation of Frozen Surimi from Surubí (Pseudoplatystome Coruscans) Using Response Surface Methodology

The effect of process temperature (2 to 18 °C), time (1 to 7 min/ cycle), and water‐mince ratio (2:1 to 8:1) on the quality attributes of surubí (Pseudoplatystoma coruscans) surimi was studied using Response Surface Methodology (RSM). Conditions were identified that allowed to achieve 25% of extracted proteins and a moisture content of 79%, compatible with an acceptable quality of surimi gel. The verification of the prediction models was acceptable. Two cryoprotectant mixtures (sucrose‐sorbitol and maltodextrin‐sorbitol) were also evaluated, with regard to the freezing and frozen storage and the functional quality of the gels. Freezing proved to be an aggressive method, and the 2 mixtures tested showed to be efficient for 6 months of frozen storage.     

Cryoprotectants improve physical and chemical properties of frozen blue crab meat (Callinectes sapidus)

The storage stability of cryogenically frozen crab meat treated with cryoprotectants was compared with pasteurised and water-treated frozen samples to determine changes in physical and chemical properties. Commercially processed, hand-picked blue crab meat was treated with solutions of polydextrose, sucrose + sorbitol/sodium tripolyphosphate or water, vacuum packaged, and cryogenically frozen prior to storage at ?29°C. All treatments were compared with an untreated reference control stored at ?65°C and a pasteurised sample stored at 1.1°C. Samples were evaluated for physical and chemical changes at 4-week intervals over 32 weeks of storage. Cryoprotectants improved oxidative stability, drip loss, expressible moisture, texture, and colour compared to untreated reference and pasteurised samples.     

Effect of some additives on the inhibition of lizardfish trimethylamine-N-oxide demethylase and frozen storage stability of minced flesh

Effects of some additives on the inhibition of trimethylamine‐N‐oxide demethylase (TMAOase) from lizardfish (Saurida tumbil) muscle were investigated. Sodium citrate and pyrophosphate could inhibit TMAOase activity in a concentration‐dependent manner, most likely because of their chelating property. Sodium alginate was the hydrocolloid possessing the inhibitory activity towards TMAOase (P < 0.05). During the storage of lizardfish mince at ?20 °C for 24 weeks, the addition of 0.5% sodium alginate and 0.3% pyrophosphate in combination with 4% sucrose and 4% sorbitol as the cryoprotectants resulted in the retarded increase in TMAOase activities with the coincidental lowered formation of dimethylamine and formaldehyde (FA), compared with the control (without additives) (P < 0.05). The loss in solubility of muscle proteins was also impeded with the addition of those compounds, suggesting their role in the inhibition of TMAOase as well as the retardation of protein denaturation induced by FA.     

Chemical Changes and Visual Appearance of Albacore Tuna as Related to Frozen Storage

Fresh albacore tuna (Thunnus alalunga) were frozen and stored at –18°C and –25°C for 1 yr. Chemical and visual analyses were carried out at 1, 3, 6, 9 and 12 mo storage. Storage time correlated (P<0.05) with the low loss of moisture at –18°C, slight reduction of TVBN at –25°C and low increases of DMA, TMA, and TBARS at both temperatures. TMAO concentration (p=0.07), drip loss on cooking (p=0.52), peroxide value (p=0.059), FFA concentration (p=0.33) and pH (p=0.20)did not change significantly with period of storage but ?25°C resulted in a lower production of DMA and FFA than ?18°C. Results from chemical analyses correlated well with basic visual appearance.     

Highly Concentrated Branched Oligosaccharides as Cryoprotectant for Surimi

Freeze-thawing studies at different concentrations, using an actomyosin solution (extracted from Alaska pollock), revealed that an 8% (w/v) solution of oligosaccharides mixture (HBOS) was most effective in cryoprotection. During frozen storage (-18°C), HBOS showed cryoprotective effects similar to sucrose and a sucrose+sorbitol mixture (1:1). Surimi gel prepared with HBOS showed higher hardness and more dense microstructure than others, although water holding capacity was slightly lower than the gel with sucrose+sorbitol. HBOS containing gel showed lower whiteness than sucrose but no difference with sucrose+sorbitol. HBOS appeared to have good potential as a non-sweet cryoprotectant of fish protein.     

Physico‐Chemical and Structural Characteristics of Vegetables Cooked Under Sous‐Vide,Cook‐Vide,and Conventional Boiling

In this paper, physico‐chemical and structural properties of cut and cooked purple‐flesh potato, green bean pods, and carrots have been studied. Three different cooking methods have been applied: traditional cooking (boiling water at 100 °C), cook‐vide (at 80 and 90 °C) and sous‐vide (at 80 °C and 90 °C). Similar firmness was obtained in potato applying the same cooking time using traditional cooking (100 °C), and cook‐vide and sous‐vide at 90 °C, while in green beans and carrots the application of the sous‐vide (90 °C) required longer cooking times than cook‐vide (90 °C) and traditional cooking (100 °C). Losses in anthocyanins (for purple‐flesh potatoes) and ascorbic acid (for green beans) were higher applying traditional cooking. β‐Carotene extraction increased in carrots with traditional cooking and cook‐vide (P < 0.05). Cryo‐SEM micrographs suggested higher swelling pressure of starch in potatoes cells cooked in contact with water, such as traditional cooking and cook‐vide. Traditional cooking was the most aggressive treatment in green beans because the secondary walls were reduced compared with sous‐vide and cook‐vide. Sous‐vide preserved organelles in the carrot cells, which could explain the lower extraction of β‐carotene compared with cook‐vide and traditional cooking. Sous‐vide cooking of purple‐flesh potato is recommended to maintain its high anthocyanin content. Traditional boiling could be recommended for carrots because increase β‐carotenes availability. For green beans, cook‐vide, and sous‐vide provided products with higher ascorbic acid content.     

Effects of Hydrolysates from Silver Carp (Hypophthalmichthys molitrix) Scales on Rancidity Stability and Gel Properties of Fish Products

This study aimed to evaluate the effectiveness of hydrolysates, which were obtained from the scales of silver carp (Hypophthalmichthys molitrix) by papain, flavourzyme, and Alcalase 2.4 L, as natural antioxidants in silver carp mince and surimi gels during storage at 4 °C. The hydrolysates that possess greater in vitro antioxidant activities (DPPH radical-scavenging activity, Fe²⁺-chelating activity, and reducing power), including hydrolysates catalyzed by papain at 10 min (HP), flavourzyme at 5 min (HF), and Alcalase 2.4 L at 5 min (HA), were chosen as additives. Color, cooking loss, conjugated dienes (CDs), thiobarbituric acid reactive substances (TBARS), fatty acids, and sensory scores of mince were measured on days 0, 2, 4, 6, and 8 during 4 °C storage; additionally, whiteness, breaking force, deformation, gel strength, and sensory score of surimi gels were measured on days 1, 3, 5, 7, 9, and 11 during 4 °C storage. The results indicate that HA was conducive to lowering the cooking loss of mince and that HF significantly (P?<?0.05) reduced the CDs value of mince. For surimi gels, HF improved whiteness, deformation, and gel strength. Hence, HF could serve as a natural antioxidant during early oxidation and improve gel formation of silver carp products.     

Inhibition of Modori (Gel Weakening) in Surimi by Plasma Hydrolysate and Egg White

The effects of beef plasma hydrolysate and egg white solids were evaluated in surimi gels using measurements of torsional shear stress and strain, bound water, cook loss and SDS-PAGE. Treatments included level of protein addition, surimi type (by species and grade) and cooking schedule. Addition of proteins, regardless of type or level of addition, significantly increased torsional shear stress and strain for all gels precooked at 60°C (90°C final cook). For gels made from low quality surimi, all levels of treatment proteins improved stress and strain for all cooking schedules and improved water holding for gels precooked at 60°C. Electrophoretic results showed a decrease in the density of the myosin heavy chain only in those gels without added proteins precooked at 60°C.     

Texture changes in frozen cod mince measured by low-field nuclear magnetic resonance spectroscopy

Studies were carried out on changes in water proton relaxation, Instron parameters, dimethylamine (DMA) content and sensory texture scores during storage of cod mince at -10°C, -20°C and -70°C. The longest transverse proton relaxation time measured by pulsed low-resolution nuclear magnetic resonance (NMR) spectroscopy increased with temperature and duration of frozen storage. These variations in the NMR parameter paralleled changes observed with analytical methods commonly used for evaluating fish texture, ie Instron measurements, as well as dimethylamine and sensory analyses. It is concluded that the NMR method can be an alternative tool to study textural modifications of cod during frozen storage. © 1997 SCI.     

PROTEIN INSOLUBILIZATION IN FROZEN GREENLAND HALIBUT (REINHARDTIUS HIPPOGLOSSOIDES)

Frozen storage of minced Greenland halibut (Reinhardtius hippoglossoides) at -10°C resulted in a rapid loss in salt solubility of “my ofibrillar proteins” (approximately 50% in 15 days) and in a gradual loss in water solubility of “sarcoplasmic proteins” (approximately 40% in 120 days). The water and salt inextractable protein from frozen mince (R) was completely soluble in 4% sodium dodecylsulfate (SDS) when a disulfide bond reducing agent such as mercaptoethanol (ME) was present. Other reagents, including urea and Triton X 100, were less effective in solubilizing the protein from mince after frozen storage. Evidence presented supports the thesis that disulfide bond formation contributes to the observed loss in protein extractability during frozen storage of mince. Addition of various thiol reagents to mince prior to freezing was effective in minimizing protein insolubilization. An estimated 50% of the reduced cysteine associated with protein is oxidized in mince after long time storage at -10°C. However, the kinetics of disulfide bond formation do not parallel the time course of protein insolubilization; accordingly, the possibility that disulfide bond formation is a secondary event cannot be excluded. Other lines of evidence indicate that additional covalent or strong bond interactions contribute to the formation of(R). Solubilization and boiling of(R) in SDS/ME does not dissociate high molecular weight aggregates (500–1000 Kdaltons) although these aggregates are disrupted by sodium borohydride reduction. In addition, the degree of hydrolysis of proteins in frozen mince by certain proteolytic enzymes is lower then that of fresh mince despite the complete solubilization of the mince protein by these proteolytic enzymes. The mince protein from frozen fish contains substantially more fluorescence than that of fresh fish. Fluorescence is associated with the high molecular weight peptide fraction after pepsin catalyzed hydrolysis. The amino acid composition of mince proteins after HCl or formic acid/HCl hydrolysis did not change appreciably as a result of frozen storage. The data indicate that covalent bond formation by sulfhydryl residues and other borohydride and acid labile linkages contribute to the loss in solubility of the protein in Greenland halibut mince during frozen storage at -10°C.     

Gel-forming ability of small scale mud carp (Cirrhiana microlepis) unwashed and washed mince as related to endogenous proteinases and transglutaminase activities

Gel-forming ability of small scale mud carp (Cirrhiana microlepis) mince and washed mince was investigated with respect to their proteinase and transglutaminase (TGase) activities. Proteinases in sarcoplasmic fluid showed the optimum activity at 65 °C and pH 9, whereas autolytic activity was maximum at 70 °C and pH 10, indicating the presence of heat-stable alkaline proteinases. When mince was washed with three volumes of water twice, TGase and proteinases were mainly removed in the first washing cycle, resulting in a decreased autolytic activity of washed mince. Breaking force of the single washed mince gels was greater than the twice washed mince and the unwashed mince gels (p<0.05). Pre-incubation of mince pastes at 40 °C for 1 h prior to cooking (90 °C/30 min) increased breaking force of all samples, particularly the single washed mince (p<0.05). This coincided with an increase of higher molecular weight polymers observed on SDS-PAGE. Washing did not completely eliminate proteinases as it was evident by an increased trichloroacetic acid (TCA)-soluble oligopeptides of washed gels pre-incubated at 55 °C. Whiteness values of washed mince gels were greater than that of mince gels.     

Texture Changes of Frozen Stored Cod and Ocean Perch Minces

During frozen storage, minced cod and ocean perch were examined by expressible moisture (EM), water binding potential (WBP) and computerized texture profile analysis (TPA). The results suggested that a microcomputer interfaced with the Instron efficiently performed TPA. The texture and water loss of all fish minces changed more rapidly at -7°C storage than at -20°C and -40°C. Furthermore, cod, a gadoid with the ability to degrade trimethylamine oxide to dimethylamine and formaldehyde, deteriorated faster than ocean perch, which did not have this ability. EM was useful for examining the water loss of frozen fish at - 7°C only during the first two weeks of storage. The WBP at -7°C storage showed a good correlation with storage time for cod and ocean perch. This suggests that WBP might be a good indicator for examining water holding ability of fish proteins.     

Structural development of sucrose‐sweetened and sucrose‐free sponge cakes during baking

The influence of sucrose, wheat starch and sorbitol upon the heat‐ and mass‐exchanging processes forming the structure of sponge cake was studied. Under the influence of wheat starch and sorbitol the structure of the sucrose‐free sponge cake was formed at more uniform total moisture release. This process was done at lower temperatures and smoother change of the sponge cake height with respect to the sucrose‐sweetened sponge cake. The porous and steady structure of both cakes was finally formed at identical time – between 18^th and 19^th minute, at the applied conditions for baking of each batter (metal pan with diameter 15.4 cm and depth 6.2 cm containing 300 g of batter and placed in an electric oven “Rahovetz – 02”, Bulgaria for 30 min at 180°C). The water‐losses at the end of baking (10.30% and 10.40% for the sucrose‐sweetened cake and sucrose‐free cake, respectively) and the final temperatures reached in the crumb central layers (96.6°C and 96.3°C for the sucrose‐sweetened cake and sucrose‐free cake, respectively) during baking of both samples were not statistically different. The addition of wheat starch and sorbitol in sucrose‐free sponge cake lead to the statistically different values for the porosity (76.15% and 72.98%) and the volume (1014.17 cm³ and 984.25 cm³) of the sucrose‐sweetened and sucrose‐free sponge cakes, respectively. As a result, the sucrose‐free sponge cake formed during baking had a more homogeneous and finer microstructure with respect to that of the sucrose‐sweetened one.     

Rapid (microwave) heating rate effects on texture,fat/water holding,and microstructure of cooked comminuted meat batters

Comminuted and gelled, fat-containing meat products such as frankfurters and luncheon meats are commercially processed by heating relatively slowly (for up to 2 h or more) to an endpoint of about 70 °C prior to cooling. This study compared such a slow, ramp heating regime (0.5 °C/min), terminated at 70 °C, to rapid, square-wave cooking (one step: rapid 100 °C/min heating to 70 °C endpoint, plus isothermal holding prior to cooling, or two-step: rapid heating to 50 °C, holding, then rapid heating to 70 °C plus holding prior to cooling) on meat batter gel properties (fracture and small strain rheology, microstructure, cook loss, and expressible water). The results indicated that a rapid cooking process, with its inherent advantages of reduced process time, lower equipment footprint, and more efficient use of energy, can produce a product nearly equivalent in textural properties and cook yield to one processed by traditional smokehouse cooking when the cook value of the processes is similar and an intermediate (near 50 °C) holding step is included (two-step rapid heating). One-step rapid heating negatively affected gel structural homogeneity and water/fat holding properties of fat-containing gels.