Jae W. Park

FISH SAUCE PRODUCTS AND MANUFACTURING: A REVIEW

Fish sauce, due to its characteristic flavor and taste, is a popular condiment for cooking and dipping. Biochemically, fish sauce is salt-soluble protein in the form of amino acids and peptides. It is developed microbiologically with halophilic bacteria, which are principally responsible for flavor and aroma. This review article covers the manufacturing methods of fish sauce, factors affecting the quality of fish sauce, nutritional values of fish sauce, microorganisms involved with fermentation, and flavor. In addition, rapid fermentation to reduce time and new parameters to estimate the quality of fish sauce are reviewed. Along with a new approach for estimating the quality of fish sauce, the quantitative analysis of degradation compounds from ATP and other specific protein compounds in fish sauce are discussed.

Thermal denaturation and aggregation of threadfin bream actomyosin

Threadfin bream (Nemipterus bleekeri) actomyosin formed insoluble aggregates at > 40 � C. Conformational changes, as measured by surface hydrophobicity, began at >30 � C and continued to increase with heating temperature. Reactive sulfhydryl groups increased as heating progressed and decreased at 50 � C, indicating the formation of disulfide linkages of threadfin bream actomyosin at >50 � C. Two distinct a-helical transition temperatures of actomyosin were found at 36.1 and 47.9 � C, while major endothemic transitions were at 38.4, 51.0, and 80.7 � C. Storage modulus (G 0 ) started to increase at 34.5 � C, implying the simultaneous occurrence of denaturation and aggregation. Gel network formation began to develop at > 41 � C.

New developments in manufacturing of Surimi and Surimi seafood

Abstract Manufacturing technology of surimi and surimi seafood has been developed to keep the balance of the quality and quantity (yield) of surimi proteins. This review article covers the chemistry of surimi manufacturing with an emphasis on solubility of myofibrillar proteins as affected by ionic strength, pH, washing cycles, wash/meat (W/M) ratio, and proteolysis. In addition, water quality, waste water, and cryoprotection are reviewed. Ohmic heating and high hydrostatic pressure in relation to the manufacturing of surimi seafood are extensively discussed. Ohmic heating is the newest technology applied in the manufacturing of surimi seafood. High hydrostatic pressure has not been applied in the commercial practices of surimi seafood manufacturing, however, it has a great potential to make surimi gels stronger.

Enzymatic hydrolysis of recovered protein from frozen small croaker and functional properties of its hydrolysates.

Fish protein isolate were recovered from frozen small croaker using pH shift. The partial enzymatic hydrolysates were fractionated as soluble and insoluble parts. They were dried using the drum dryer and their functional properties were examined. The total nitrogen content of the enzymatic hydrolysates ranged from 12.9% to 13.7%. The degree of hydrolysis of precipitates was 18.2% and 12.2% for croaker hydrolysates treated with Protamex 1.5 MG (Bacilllus protease complex) and Flavourzyme 500 MG (endoproteases and exoproteases, Aspergillus oryzae), respectively. The TCA supernatant, after centrifugation of hydrolysates, contained numerous peptides ranging from 100 to 4000 daltons. The solubility of the supernatants was higher than that of the precipitates at 0% to 3% NaCl and pH 2 to 10. The precipitate of Flavourzyme- and Protamex-treated hydrolysates showed a high emulsion activity index value compared to egg white and bovine plasma protein. In addition, the highest emulsion stability was observed for Protamex-treated precipitate hydrolysates. Emulsion stability of Protamex-treated precipitate hydrolysates was comparable to those of protein additives (egg white, bovine plasma protein, and soy protein concentrate). Water and fat binding capacity of precipitates were higher than those of supernatant. The results indicate that precipitate hydrolysate from undersized croaker can be used in processed muscle foods as a functional and nutritional ingredient.

Photoprotection for deltamethrin using chitosan-coated beeswax solid lipid nanoparticles

BACKGROUND In the natural environment, photodegradation is one of the most common degradative processes of pesticides. In order to reduce the photodegradation of pesticides, and so increase their killing activity against target pests, chitosan-coated beeswax solid lipid nanoparticles (CH-BSLNs) were prepared by a combination of hot homogenization and sonication, with deltamethrin as an active ingredient. RESULTS Under optimal conditions, the highest encapsulation efficiency (95%) and a high payload of deltamethrin (approximately 12.5%) were achieved. In direct photolysis, in the case of CH-BSLNs after UV irradiation for 24 h, 37.3% of deltamethrin remained, as opposed to only 14.6% of the free-form deltamethrin. In addition, in indirect photolysis, in the case of CH-BSLNs after UV irradiation for 2 h in 2% acetone solution, approximately 74.5% of deltamethrin remained, as opposed to only 37.6% of the free-form deltamethrin. CONCLUSION CH-BSLNs showed good protection for deltamethrin against photodegradation. This novel nanocarrier may be useful in crop protection as an economical strategy to enhance the effect of pesticides in the field and protect the environment as well.

Structural changes and dynamic rheological properties of sarcoplasmic proteins subjected to pH-shift method.

Structural changes and dynamic rheological properties of sarcoplasmic proteins from striped catfish ( Pangasius hypophthalmus ) treated by various pH-shift processes were investigated. Isoelectric precipitation of acid-extracted sarcoplasmic proteins led to the lowest solubility in water. Sarcoplasmic proteins were unfolded after extremely acidic and alkaline extraction, exposing tryptophan and aliphatic residues. The alpha-helical structure was converted to beta-sheet following acidic extraction, whereas alkaline treatment did not disturb the alpha-helical structure of sarcoplasmic proteins. Disulfide formation, hydrogen bonding via tyrosine residues, and hydrophobic interactions occurred under extreme pH extraction. Acidic extraction induced denaturation and aggregation of sarcoplasmic proteins to a greater extent than did alkaline treatment. Hydrophobic interactions via aliphatic and aromatic residues were formed during isoelectric precipitation. Sarcoplasmic proteins were partially refolded after isoelectric precipitation followed by neutralization. Sarcoplasmic proteins prepared from an alkaline pH-shift process readily aggregated to form a gel at 45.10 degrees C, whereas higher thermal denaturation temperatures (>80 degrees C) and gel points ( approximately 78 degrees C) were observed in acid-treated sarcoplasmic proteins. The pH condition used for extraction, precipitation, and neutralization greatly affected structural changes of sarcoplasmic proteins, leading to different thermal and dynamic rheological properties.

Negative roles of salt in gelation properties of fish protein isolate.

Salt effect on gelling properties of fish protein isolate (FPI) prepared by acid- and alkali-aided extraction was investigated. Acid- or alkali-extracted FPI formed significantly better gel texture with 0% NaCl than with 3% NaCl. Texture properties of acid- or alkali-extracted FPI decreased as NaCl content increased, especially at 2% to 3% salt. Contrarily, salt significantly promoted texture qualities of conventional surimi gels. The effect was highlighted when they were subjected to low temperature setting. The myofibrillar proteins in FPI were not solubilized when NaCl was added, perhaps due to protein aggregation caused by acid or alkali extraction. FPI solubility, however, was not closely related to their texture properties. Cold setting did not promote texture properties of FPI gels as much as conventional surimi gels. Acid-extracted gels gave the best color properties.

Gel Forming Ability of Tropical Tilapia Surimi as Compared with Alaska Pollock and Pacific Whiting Surimi

Abstract Setting and thermal treatment effects on texture and color of tropical tilapia surimi gels were compared to Alaska pollock and Pacific whiting gels. Heat treatments that most favored intrinsic gelling factors of a fish species exhibited strong gel formation. Whiteness values increased as total thermal inputs increased, which reflect the increasing opacity of the gels. Pollock gels were generally the strongest and whitest. Tilapia gel quality was generally second to pollock gels, however, in heat treatments using setting temperatures ≥ 40 °C, tilapia gels were comparable (60 °C setting) or superior (40 °C setting) to pollock gels. The optimum heat treatment for tilapia surimi appeared to be a 40° C setting for 1 hr followed by a 90 °C cook for 15 min. SDS-PAGE patterns of gels prepared with 60°C setting followed by 90 °C cooking elucidated the various degree of protein degradation depending upon the species in a descending order of whiting, tilapia, and pollock.

Qualification and Quantification of Fish Protein in Prepared Surimi Crabstick

Species identification and protein quantification in surimi crabstick were achieved using sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE). When the Lowry and Kjeldahl protein determination methods were compared, the former showed more consistent results. Densitometric scanning of the gels was used for quantification of total fish protein as well as total egg white protein. The lower molecular weight proteins, 30 kDa and lower, proved to be the most useful in fish species identification as well as egg white protein addition. Using a combination of the myosin heavy chain band and the species-specific myosin light chain (Alaska pollock: 22.5 kDa; Pacific whiting: 24.4 kDa) proved the most accurate in calculating fish protein content of the crabstick sample, while for those samples that contained egg white, quantification was accomplished from the densitometric analysis of the overlapping bands of actin (45 kDa) from fish and ovalbumin from egg white. Lysozyme (14.3 kDa) proved to be a unique protein band in determining the presence of egg white when the content of dried egg white was equal to or exceeded 0.5% of the total weight of the final crabstick.

Biochemical characterisation of Alaska pollock, Pacific whiting, and threadfin bream surimi as affected by comminution conditions

Salt-soluble protein, surface reactive sulfhydryl content, and surface hydrophobicity of Alaska pollock, Pacific whiting, and threadfin bream surimi were characterised, as affected by various comminution conditions. Chopping time/temperatures were explored in consideration of their habitat temperatures. Salt-soluble protein (SSP) significantly decreased when chopping time was extended. Corresponding to our follow-up study, no relationship between SSP and gel texture was found. Surface hydrophobicity was inversely proportional to SSP concentration, indicating the unfolding of protein upon comminution. Alaska pollock surimi demonstrated aggregation during chopping at 10 and 20 °C, based on the surface hydrophobicity. Surface reactive sulfhydryl (SRSH) contents of the three fish species behaved differently. The SH groups were oxidized to disulphide bonds when higher chopping temperature was applied. As a result, increased SRSH content was not observed in Alaska pollock (10 and 20 °C chopping) and threadfin bream paste (25 and 30 °C chopping).