Profiles of New Zealand Snapper (Pagrus auratus) Postmortem Metabolism as Affected by Acclimated Temperature and Postmortem Storage Temperature

ABSTRACT: Chemical anesthesia (AQUI-S^TM) was used to harvest tank-reared snapper ( Pagrus auratus ) from late summer (19.6 °C) and winter (11.9 °C) acclimated populations in a "rested" state. Carcasses were stored in seawater at temperatures between 2 and 20 °C to investigate the effects of acclimation and storage temperature on the postmortem metabolic rate. Contour plots of postmortem muscle pH [lactic acid] and adenosine triphosphate/inosine monophosphate measurements revealed critical temperature transitions: 16 to 18 °C (coinciding with seasonal behavioral changes) and 4 to 6 °C (consistent with cold injury). DC eye surface potential (ESP) was evaluated as a noninvasive indicator of tissue-temperature interactions and showed similar patterns of critical temperature transitions.     

Isolation and Characterization of Chitinase‐Producing Bacillus and Paenibacillus Strains from Salted and Fermented Shrimp,Acetes japonicus

Chitinases catalyze the conversion of chitin and are produced by a wide range of bacteria. The biological applications of these enzymes have been exploited in food and pharmaceutical industries. We isolated 2 halophilic chitinase‐producing novel strains of bacteria—SCH‐1 and SCH‐2 from Saeu‐jeot, a traditional Korean salted and fermented food made with shrimp (Acetes japonicus). The isolated strains‐ SCH‐1 and SCH‐2 were Gram‐positive, rod‐shaped, endospore‐forming facultative anaerobes, with strain SCH‐2 showing peritrichous flagella. Molecular characterization of the 16S rRNA gene identified the strains SCH‐1 and SCH‐2 as Bacillus sp. and Paenibacillus sp. respectively. Basic Local Alignment Search Tool and subsequent phylogenetic analysis of strain SCH‐1 showed an identity of 97.83% with Bacillus cereus ATCC 14579 (NR_074540), whereas strain SCH‐2 showed an identity of 99.16% with Paenibacillus lautus JCM 9073 (NR_040882). Furthermore, the SCH‐1 strain could use glucose, N‐acetyl glucosamine, esculin, and maltose as carbon source substrates. Cellular fatty acid analysis showed that iso‐C_15:0 and anteiso‐C_15:0 are the major acids in strain SCH‐1 and SCH‐2, respectively. The SCH‐1 strain showed a higher chitinase activity at 15.71 unit/mg protein compared with SCH‐2 strain. Chitinase isozymes of Bacillus sp. SCH‐1was expressed as 2 bands having sizes of 41 and 50 kDa, and as 4 bands with sizes of 30, 37, 45.7, and 50 kDa in Paenibacillus sp. SCH‐2. The rich chitinase activity with the isozyme profiles of the isolated Bacillus and Paenibacillus strains provide advancement in the study of fermentation and may play putative functions in the chitin bioconversion of sea crustacean foods.     

Processing Properties of Beef Semimembranosus Muscle as Affected by Electrical Stimulation and Postmortem Treatment

Semimembranosus muscles from paired sides-electrically stimulated (ES) and not-stimulated (NES)-of mature cows were used to determine effects of certain postmortem treatments (state of rigor/temperature) and of ES on processing properties. ES decreased (P<0.05) pH values for prerigor, prerigor/frozen and postrigor/frozen muscles, but did not affect (P>0.05) values for total protein or juice loss during cooking. State of rigor/temperature treatment affected pH and salt-soluble protein (SSP) values more than did ES treatment. pH values differed (P<0.05) between each state of rigor/temperature treatment for both ES and NES samples. Salt-soluble protein values were higher (P<0.05) for NES prerigor than for NES postrigor/frozen samples and higher (P<0.05) for NES postrigor than for NES postrigor/frozen samples. SSP values for ES muscles were higher (P<0.05) for ES postrigor samples than for ES postrigor/frozen samples but were not different for other comparisons. Regardless of ES treatment, freezing of semimembranosus muscles increased pH values (P<0.05) and decreased SSP values (P<0.05) in three of four comparisons.     

Characteristics of Beef Batters as Influenced by Electrical Stimulation and Postmortem Salting Time

Changes were evaluated in functional and textural properties of beef batters altered by mincing, postmortem salting time and electrical stimulation. Histological examinations showed raw batters from non-stimulated (NS) meat exhibited uniform fat dispersal throughout the protein matrix regardless of salting time; however, fat channeling, increased fat and gel-water release, lower hardness and gel strength along with reduced apparent viscosity were observed in electrically stimulated (ES) meat when salting was delayed. Changes in amounts of salt-soluble protein were not consistent. Effects of pH on water-holding capacity and myofibrillar swelling accounted for most changes observed in batters from ES muscles. However, increases in apparent viscosity and hardness may have been a consequence of rigor onset.     

Akara (Fried Cowpea Paste) Quality as Affected by Frying/Reheating Conditions

Three factors (initial cooking time, reheating time, and reheating oil temperature) at three levels each were studied to determine effects on consumer acceptance of partially cooked, frozen, reheated akara. Based on consumer panel results, initial cooking time should be more than 50 sec to obtain acceptable akara. With 75 set initial cooking time (ICT), reheating time (RT) should be at least 50 set, while reheating oil temperature (ROT) should range from 152–180°C. RT should be more than 70 set and ROT not exceed 180°C when 100 set ICT is applied. Trained sensory panel testing and instrumentahchemical measurements verified that the quality of akara from recommended processing conditions was close to that of fresh akara.     

Proteolysis and Functional Properties of Mozzarella Cheese as Affected by Refrigerated Storage

Each of three cheese batches was randomly divided into two parts, one was subjected to slow freezing for 15 days and the other maintained under refrigeration. Thereafter the cheeses were tempered under refrigeration for 1 mo and evaluated weekly. In general, cheeses presented low melting capacity as a result of low levels of proteolysis. This low intensity of proteolysis was probably a function of the destruction of the lactic starter and partial inactivation of the coagulant during stretching of the cheese. Free oil content increased during storage for both treatments, but more in the tempered samples.     

Physicochemical Properties of Pacific Whiting Surimi as Affected by Various Freezing and Storage Conditions

ABSTRACT: Effects of various freezing methods of surimi on the biochemical and physical properties, were examined. Stress values increased up to 3 mo and then decreased. Strain values significantly decreased over time, except freeze-dried surimi stored at -18 °C. Yellowness (b*) of the freeze-dried surimi stored at 22 °C increased significantly during storage. In addition, salt-extractable proteins (SEP) decreased while dimethylamine (DMA) increased. Freeze-dried surimi showed the highest SEP and the lowest DMA values after 9 mo storage. Electrophoretic patterns did not show any apparent damages to the MHC until 6 mo. At 6 and 9 mo, development of proteins with smaller molecular weights was observed, indicating proteolytic degradation during frozen storage.     

Color Stability and Lipid Oxidation of Rockfish as Affected by Antioxidant from Shrimp Shell Waste

Crude and partially purified antioxidants from shrimp shell waste were obtained by ethanol extraction and silica gel column chromatography. Whole rockfish ( Sebastolobus alascanus, Sebastes ruberriumus ) samples were treated with crude antioxidant solution dips while another species of rockfish fillets ( Sebastes alutus ) was treated with various concentrations of partially purified antioxidant solution dips from column chromatography. Higher a* values were found in all rockfish samples treated with antioxidants compared to the control. The partially purified antioxidant from shrimp shell waste significantly lowered TBA values compared to the untreated water-dipped control rockfish fillets ( Sebastesalutus ).     

Rheological Properties of Chymosin-Induced Skim Milk Gels as Affected by Milk Storage Time and Temperature

Fundamental dynamic rheological tests were used to measure the rigidity (|G*|) and viscoelasticity (tan δ) of gels made from skim milk samples that were (1) never cooled, (2) stored at 4°C, or 3) stored at 4°C and then rewarmed to 25°C. Milk cooled and held at 4°C prior to gel formation produced gels with lower |G*| and higher tan(δ) than fresh milk gels. Chilled milk samples that were rewarmed to 25°C for 16h prior to gel formation produced gels with rheological properties similar to fresh milk gels. The solubilization of β-casein during cold storage was hypothesized to be the cause of observed differences in gel rheology.     

Interconversions of Isoflavones in Soybeans as Affected by Storage

ABSTRACT: Conversions of isoflavones in soybeans under 4 conditions were investigated. Soybeans were stored in 84% RH, 30 °C for 9 mo and in 57% RH, 20 °C, cold (4 °C), and an uncontrolled ambient garage for 18 mo. Isoflavones were analyzed by HPLC. In 84% RH, 30 °C, the interconversion between aglycones and β-glucosides was significant ( p < 0.001). The percentage of β-glucosides and malonylglucosides in total isoflavones decreased from 99% to 3% in 9 mo. In contrast, the aglycones increased from 1% to 97%. In 57% RH, 20 °C, and ambient conditions, the glucoside forms increased with storage time, but malonylglucosides tend to decrease. In the 4 °C condition, isoflavone distribution had no significant ( p > 0.05) changes during storage.     

Chitosan Film Mechanical and Permeation Properties as Affected by Acid, Plasticizer, and Storage

The effects of acid (acetic, formic, lactic, propionic) concentrations, plasticizer concentrations, and storage time (up to 9 wk) on mechanical properties, water vapor permeability, and oxygen permeability of solution-cast chitosan films were determined. Measured water vapor permeability coefficients ranged from 5.35 to 13.20 × 10^?1 g/m·day·atm. Oxygen permeated coefficients ranged from 0.08 to 31.67 × 10^?3 cc O₂ m·day·atm. Neither property was affected by storage time. Tensile strength (6.85–31.88 Mpa) also was not time dependent, but elongation (14–70%) decreased with storage time. Lactic acid solutions produced the lowest oxygen permeability values, formic acid the highest. Films formed with 7.5% lactic acid solutions had uniquely high values for elongation at break.     

Use of Cryoprotectants to Stabilize Functional Properties of Prerigor Salted Beef During Frozen Storage

Changes in functional properties (gelforming ability, water-holding capacity, and protein solubility) of salted prerigor beef and postrigor beef were measured over 6 months frozen storage at ?28°C, as affected by addition of 5.6% cryoprotectants [Polydextrose® or a mixture (1:1) of sucrose and sorbitol]. Addition of NaCl to comminuted muscle prior to freezing accelerated destabilization of muscle proteins with respect to functional properties. This effect was reduced by cryoprotectants; most effectively by sucrose/sorbitol and only slightly less effectively by polydextrose. As evidenced by the parameters investigated, quality of prerigor salted muscle treated with cryoprotectants and stored 6 months was approximately equal to that of untreated postrigor meat prior to freezing.     

Heat-Induced Aggregation Properties of Whey Proteins as Affected by Storage Conditions of Whey Protein Isolate Powders

The control of storage as any other manufacturing steps of dairy powders is essential to preserve protein functional properties. This study aimed to determine the effects of different storage conditions on both protein denaturation and protein lactosylation in whey protein isolate (WPI) powder, and also on heat-induced aggregation. Two different storage temperature conditions (20 and 40 °C) were studied over 15 months. Our results showed that protein lactosylation progressively increased in WPI powders over 15 months at 20 °C, but heat-induced aggregation properties did not significantly differ from non-aged WPI. On the other hand, powders presented a high level of denaturation and aggregation at 40 °C from the first 2 weeks of storage, involving first protein lactosylation and then aggregation in the dry state. This was correlated with an increasing Browning Index from 15 days of storage. These changes occurred with a decrease in aggregate size after heat treatment at 5.8?≤?pH?≤?6.6 and modification of heat-induced aggregate shapes.     

Foaming Properties of Proteins as Affected by Concentration

Commercial sodium caseinate and whey protein isolate were evaluated at protein concentrations 0.25 to 16% with ovalbumin solutions as reference. Logarithmic models were developed to express the effect of protein concentration on foam expansion and serum drainage. The kinetics of gas release from milk protein-stabilized foams followed a three-phase pattern. Low foam collapse rates were observed in initial and final phases while rapid collapse occurred during the transition phase. No transition was observed for ovalbumin-stabilized foams. Globally, foam collapse rate increased with increasing protein concentration. Apparent viscosity of protein-stabilized foams increased with concentration to a maximum; beyond which, a reverse trend was observed. Maximum viscosities of milk protein foams were at concentrations & lt;0.5%, while ovalbumin foams showed maximum viscosity around 2% protein.     

Yield and Textural Properties of Tofu as Affected by the Changes of Phytate Content During Soybean Storage

ABSTRACT: Soybeans stored under 4 conditions were analyzed for the degradation of phytate and its effects on tofu qualities. Phytate in soybeans was hydrolyzed significantly under the adverse conditions for 9 mo, but decreased slightly under 3 mild conditions for 18 mo. Phytate degradation contributed to an increase in titratable acidity. When the phytate contents of soymilk were selectively reduced by 11.3% and 17.5% by phytase, while other components remained unchanged, tofu yield increased significantly but texture became softer. Tofu yield decreased and hardness increased in beans stored in the adverse conditions. Phytate degradation during adverse storage played a minor, indirect role in the deterioration of soybeans for tofu making.     

Physicochemical Properties of Frozen Red Hake (Urophycis chuss) Mince as Affected by Cryoprotective Ingredients

ABSTRACT: Effects of alginate, iota-carrageenan, soy protein concentrate (SPC), sodium tripolyphosphate (STPP), and sorbitol on physicochemical and sensory properties of red hake mince stored at −20 °C for 17 wk were investigated. The addition of 0.4% alginate, 4% sorbitol, and 0.3% STPP kept the mince from hardening and improved its dispersibility during mixing. This is believed to be a result of reduced protein denaturation as evidenced by higher levels of water, salt, SDS-soluble proteins, and higher free sulfhydryl contents than the untreated control mince, which hardened with compact texture and exhibited considerable syneresis. Alginate appears to be responsible for preventing muscle fiber interaction through electrostatic repulsion and chelating Ca²⁺, thus improving dispersibility. Sorbitol and STPP with or without SPC and iota-carrageenan did not improve the dispersibility.     

Gel Properties of Surimi from Various Fish Species as Affected by Moisture Content

Torsion, punch, and color tests as affected by moisture content were evaluated for surimi from pollock, Pacific herring, arrowtooth flounder, and Pacific whiting. Torsion stress and strain decreased linearly with increased moisture content but strain values were less sensitive to moisture than were stress values. This finding enabled mathematical normalization of torsion stress and strain values rather than adjusting the moisture content of samples prior to testing. Punch test results, while linearly related to moisture content, were not as consistent as torsion test results. The L* and whiteness increased with higher moisture content, but changes in a* and b* values were not consistent for surimi from different species.     

Preservation of Grayfish (Squalus acanthias) by Salting

Grayfish (Squalus acanthias) fillets were preserved by an improved salting technique with pre-brining procedure along with ascorbic acid treatment in order to retard rancidity. The protein loss during salting was 2.4% and more than 2/3 fatty acid content of salted fillets decreased over 8 wk of storage at 20°C. The added ascorbic acid had an antioxidative effect for 2 wk of storage, after which the TBA values rose sharply. The organoleptic evaluation indicated no significant decrease in flavor until after 4 wk of storage. Statistical T-test showed no significant differences for appearance, odor, and texture among salted grayfish and salted cod fillets.     

Physical Properties of Climbing Black Pepper (Piper nigrum) and Alligator Pepper (Aframomum melanguata) as Affected by Dehydration

This study was conducted to determine effect of drying temperature and duration on selected physical properties of climbing black pepper (Piper nigrum) and alligator pepper (Aframomum melanguata) using response surface approach. Drying temperature (55.86, 60, 70, 80, 84.14 °C) and duration (2.59, 3, 4, 5, 5.414 hours) were variables while size (length, breadth, thickness), mass, sphericity, aspect ratio, moisture content, moisture loss, colour and bulk density were responses. Mass, density and moisture loss of climbing pepper were significantly affected by drying temperature and duration at 5% level of significance. Other climbing pepper physical properties under study were not influenced significantly. All alligator pepper properties considered were not significant (p > 0.05). Climbing pepper mass, density and moisture loss varied between 1.55 to 6.37 g, 0.17 to 0.59 g/ml and 31.1 to 84.0% respectively.     

Functional Properties of Cowpea Paste as Influenced by Indigenous Microflora

The influence of indigenous microorganisms on several functional properties of cowpea (Vigna unguiculata) paste was investigated. Six formulas [with and without onion, salt and pepper; inoculated (indigenous microflora) and uninoculated] were prepared and incubated for 24 hr at 30°C. Lactic acid bacterial populations were similar to total aerobic microbial populations which increased with time of incubation. Pastes containing salt were associated with high equilibrium moisture contents. As incubation time progressed, pH and emulsion capacity decreased and specific gravity and apparent viscosity increased, while oil and water binding capacity remained unchanged. Formula content and incubation time did not influence the color of cowpea pastes; however, akara, a deep-fat fried product prepared from the paste, did have a darker color when made from paste which had been incubated for 24 hr.