Determination of Optimal Level of Lactitol for Surimi

Cryoprotective effects of lactitol dihydrate at 2, 4, 6 and 8% levels in cod surimi were investigated and compared to an industrial control (1:1 mixture of sucrose/sorbitol at 8% w/w) and to a control without additive. Stability of protein functional properties was monitored by salt extractable protein and differential scanning calorimetry analyses, as well as texture profile analyses of cooked gels for surimi stored at ? 12°C for 8 wk. Data revealed the excellent cryoprotective properties of lactitol. Moreover, the level of lactitol in surimi could be reduced to 5.7–6.4% w/w without significant alteration of stabilizing effects.     

The effect of low- or non-sweet additives on the stability of protein functional properties of frozen cod surimi

The cryoprotective effect of low- or non-sweet additives, Palatinit^R, Polydextrose^R, casein hydrolysate and fish protein hydrolysate (at 8% w/w) as well as lactitol (at 4% and 8% w/w) were compared to an industrial control containing sucrose/sorbitol (8% w/w) and a control without additive in cod surimi stored at –20°C for 4 months. Freeze-induced protein denaturation was evaluated monthly by salt extractable protein and differential scanning calorimetry analyses of surimi followed by texture and expressible moisture analyses of surimi cooked gels. Results revealed that protein functionality was similarly maintained during frozen storage by lactitol, Palatinit^R and Polydextrose^R when incorporated in cod surimi at the 8% level. Surimi gels could be produced with textural attributes comparable to 8% w/w sucrose/sorbitol surimi gels, and the level of lactitol in cod surimi could be reduced to 4% w/w without significant alteration of cryoprotection. Some benefits in gel-forming properties were obtained by adding 8% casein hydrolysate to cod surimi.     

Cryoprotective Effects of Sugar, Polyols, and/or Phosphates on Alaska Pollack Surimi

Freeze-induced protein denaturation of pollack surimi was investigated as affected by the addition of sugar and/or polyol, including a starch hydrolysate product, and/or phosphates during 8 months frozen storage. Polydextrose® appeared to substitute for the sucrose/sorbitol now used in surimi manufacture without changes in cryoprotective effect. The maltodextrin adversely affected gel-forming properties, although it maintained the salt-soluble protein extractability nearly as well as did sucrose/sorbitol or Polydextrose®. The cryoprotective effects of phosphate addition seemed to depend upon the pH and/or specific phosphate ion used.     

Cryoprotective Effects of Some Materials on Cod-Surimi Proteins during Frozen Storage

Freeze-induced protein denaturation of cod surimi was studied as affected by carbohydrates (sucrose and glucose syrup at 8% w/w), polyols, (sorbitol and glycerol at 8% w/w), protein hydrolysates (fish protein and casein hydrolysates at 4% w/w), hydrocolloids (pectin-1% w/w, sodium alginate, lambda- and iota-carrageenan-0.5% w/w) and combinations of the above, (sucrose/sorbitol 1:1 mixture at 8% w/w, or combined with protein hydrolysates at 4% w/w). Salt extract-able protein (SEP) and heat induced denaturation by differential by differential scanning calorimetry (DSC) were used to monitor protein changes in surimi stored 16 wk at -20°C. The best cryoprotection effect was achieved from sorbitol, glucose syrup (DE = 60), sucrose and sucrose/sorbitol 1:1 w/w mixture at 8% w/w in surimi. Correlations between certain DSC parameters and SEP were high.     

Cryoprotective effects of trehalose and sodium lactate on tilapia (Sarotherodon nilotica) surimi during frozen storage

The cryoprotective effects of trehalose and sodium lactate at level of 8% (w/w) in tilapia surimi were studied in comparison with a conventional cryoprotectant (sucrose/sorbitol, 1:1) during extended storage at −18 °C for up to 24 weeks. All present cryoprotectants retarded the protein changes as evidenced by the lowered decrease in salt extractable protein (SEP), Ca²⁺-ATPase activity, total sulfhydryl content as well as the impeded increase in disulfide bond content and surface hydrophobicity. The gel-forming ability of frozen surimi was more retained with addition of cryoprotectants. Among all cryoprotectants used, trehalose exhibited the greatest protective effect on protein denaturation as shown by the effectiveness in maintaining Ca²⁺-ATPase activity and protein solubility. Additionally, the greatest breaking force and deformation were obtained in surimi added with 8% trehalose throughout the frozen storage up to 24 weeks. Sodium lactate showed a similar cryoprotective effect to sucrose/sorbitol blend. Therefore, trehalose and sodium lactate appeared to be promising alternative cryoprotectants for surimi owing to their low sweetness and caloric value.     

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.     

EFFECTS OF CRYOPROTECTANTS IN MINIMIZING PHYSICOCHEMICAL CHANGES OF BOVINE NATURAL ACTOMYOSIN DURING FROZEN STORAGE1

Physicochemical changes in bovine natural actomyosin extracted from prerigor semimembranosus muscle were investigated during frozen storage at ?28°C as affected by the addition of cryoprotectants (5.6% Polydextrose® or 5.6% mixture (1:1) of sucrose and sorbitol). Proteins were destabilized during freezing and frozen storage as reflected by decreases in protein solubility, the visual appearance of aggregates in protein sols, decrease in intensity of flow birefringence, intrinsic viscosity and ATPase activity, and changes in size, shape, or charge of the protein (especially myosin) as evidenced by nondenaturing electrophoresis. These effects were reduced to some extent by the two cryoprotectant treatments.     

海藻糖、乳酸钠对冻藏鳙鱼鱼糜蛋白抗冻效果的影响

以凝胶强度、盐溶性蛋白含量、Ca~(2+)-ATPase活性、总巯基、表面疏水性为指标并结合DSC分析(差示扫描量热分析),研究了海藻糖、乳酸钠在8%(w/w)水平上对鳙鱼鱼糜蛋白在-18℃冻藏24周的抗冻效果,并将其抗冻效果与传统商业抗冻剂(4%蔗糖+4%山梨糖醇)进行了对比。结果表明,海藻糖、乳酸钠的加入能较好地抑制冻藏鳙鱼鱼糜蛋白的冷冻变性,表现在这2种物质加入后,冻藏鳙鱼鱼糜的凝胶能力得到较好的维持,盐溶性蛋白含量、Ca~(2+)-ATPase活性和巯基含量的下降及表面疏水性的增加也得到很好的抑制,2种物质的抗冻效果比传统商业抗冻剂具有明显的优势。DSC分析表明,抗冻剂的添加可能改变了鳙鱼鱼糜肌球蛋白的结构,使其变得更稳定,从而表现出较好的冻藏稳定性。海藻糖、乳酸钠都属于低甜度、低热值物质,因此在鱼糜加工业中有望成为传统商业抗冻剂的替代物。     

Combined Effects of Phosphates and Sugar or Polyol on Protein Stabilization of Fish Myofibrils

Stabilization of fish myofibrils was investigated with respect to freeze-and heat-induced denaturation as affected by the addition of phosphates (0.25, 0.5% of sodium tripolyphosphate or neutralized pyrophosphate), alone or in combination with 8% Polydextrose® or a sucrose/sorbitol mixture. Freeze-induced aggregation was reduced effectively by combination of phosphates and carbohydrates, and, less effctively, by phosphates or carbohydrates alone. The most effective treatment consisted of 0.5% of either phosphate treatment combined with either carbohydrate treatment. Differential scanning calorimetric studies revealed that phosphate addition induced stabilization of myosin and carbohydrate addition generally induced a one-step denaturation process for myosin. No differences due to phosphate type were observed in any measured parameter.     

Effects of konjac glucomannan on physicochemical properties of myofibrillar protein and surimi gels from grass carp (Ctenopharyngodon idella)

The cryoprotective effect of konjac glucomannan (KGM) on myofibrillar protein from grass carp (Ctenopharyngodon idella) during frozen storage at −18 °C and the influence of five levels of KGM (0%, 0.5%, 1%, 1.5%, and 2%) on texture properties, water-holding capacity, and whiteness of grass carp surimi gels were investigated. KGM as a novel cryoprotectant could significantly mitigate the decrease in salt extractable protein (SEP), Ca²⁺-ATPase activity, and total sulphydryl and active sulphydryl contents of myofibrillar protein during frozen storage. KGM at the level of 1% showed the same good cryoprotective effect as a conventional cryoprotectant (10% sucrose–sorbitol, 1:1, w/w). As the levels of KGM increased, breaking force and deformation of grass carp surimi gels increased significantly. Water-holding properties of the surimi gels are improved with the increasing addition of KGM, but the whiteness decreased and the colour became darker. The optimum addition level of KGM was suggested to be 1%.     

抗冻剂在冷冻鱼糜生产中的应用

研究了不同抗冻剂对冷冻鱼糜性能的影响。实验结果表明,添加抗冻剂低聚糖、蔗糖、山梨醇可以有效地防止鱼糜在冷冻过程中蛋白发生变性,并能提高冷冻鱼糜的凝胶强度,混合磷酸盐能有效的提高冷冻鱼糜的保水性。通过试验得出,4种抗冻剂的优化配比是:低聚糖4%,山梨醇2%,蔗糖1%,混合磷酸盐0.3%,生产的冷冻鱼糜凝胶强度最高可达14 148.1 g/cm2。     

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.     

Chemical Stability of Antioxidant-Washed Beef Heart Surimi During Frozen Storage

Beef heart surimi was prepared in the presence or absence of propyl gallate and blended with or without cryoprotectants (sucrose, sorbitol). Samples were stored at -15, -29, and -70°C for 0.2, 2, 4, 12, 26 and 52 wk to observe oxidative changes in lipids (TBARS and dienes) and proteins (sulfhydryl, carbonyl, surface hydrophobicity, and myosin ATP-ase). Lipid and protein oxidation was minimal at -70°C. The freeze-thaw process caused lipid and protein oxidation in control samples at -15 and -29°C. Oxidation increased rapidly after 4 wk. Propyl gallate inhibited lipid oxidation but was ineffective against protein changes. After 12 wk, cryoprotectants promoted lipid and protein oxidation in the absence of propyl gallate.     

Functional Stability of Antioxidant-washed, Cryoprotectant-treated Beef Heart Surimi During Frozen Storage

Beef heart surimi was prepared in the presence or absence of propyl gal late and blended with or without cryoprotectants (sorbitol, sucrose) prior to frozen storage at 15°, 29°, and 70°C up to 52 wk. Protein solubility, gelling characteristics, water-holding capacity, cooking yield, and emulsifying properties decreased during storage at 15° and 29°C for control surimi (without cryoprotectants). Propyl gallate alone did not influence functionality changes. However, functional properties were largely protected by cryoprotectants as well as at 70°C independent of cryoprotectants. Thus, unless extremely low temperatures are used, beef heart surimi subjected to long-term cryogenic storage should be mixed with cryoprotectants and antioxidants to preserve functionality.     

Cryoprotection of frozen-stored actomyosin of farmed rainbow trout (Oncorhynchus mykiss) by some sugars and polyols

A study on the effectiveness of several cryoprotectants (polydextrose, lactitol, glucose syrup and a mixture of sucrose and sorbitol [1:1]) in preventing freeze-induced perturbations of fish proteins was carried out in in vitro systems of natural actomyosin of rainbow trout (Oncorhyncus mykiss) muscle. Adding these cryoprotectants prevented drastic decreases of ATPase activity, as well as a rapid exposure of hydrophobic and sulphydryl groups on the protein surface. Cryoprotectants therefore slowed down the kinetics of aggregation via intermolecular secondary forces and disulphide bonds, thus greatly reducing losses in solubility.     

CHANGES IN PROXIMATE COMPOSITION OF THORNBACK RAY (RAJA CLAVATA, L. 1758) SURIMI DURING WASHING AND FROZEN STORAGE

The effects of frozen storage of surimi produced from thornback ray and the washing of mince on the chemical composition were investigated. The crude ash content which was initially found as 1.38% in raw thornback ray decreased approximately 12 and 80% after the first and second washing, respectively. After the third washing, crude ash content increased to 207% of the amount in the second washing because of addition of salt to the last washing water. The crude protein content of mince also decreased approximately to 28 and 20% after the first and second washing, respectively. After the third washing, the decrease in the lipid levels was approximately 30%. At the end of 6 months of frozen storage at − 23.8  ±  2C, dry matter, crude ash and crude protein contents increased in a greater ratio in surimi containing 4% sorbitol, 4% sucrose and 0.3% Na-tripolyphosphate than surimi prepared with 8% sorbitol and 0.3% Na-tripolyphosphate.

PRACTICAL APPLICATIONS

In the present study, the effects of frozen storage of surimi produced from thornback ray and the washing of mince on the chemical composition were investigated. Washing procedure significantly decreased crude ash, crude protein and crude fat content of mince. There were significant differences in moisture, crude ash, and crude protein contents during the 6 months storage period of frozen surimi obtained by using different cryoprotectant mixtures. The folding test scores were highest in fresh surimi and during the first two months of storage. Thornback ray can be used for the production of surimi.     

Salt-free Miso Fermentation Using Ethanol, Sugars, and Polyols

Steam-cooked soybeans mixed with rice koji (2:1, w/w) were ground into a fine paste, combined with NaCl or sucrose, and supplemented with ethanol for miso fermentation at 28 °C for 8 wk. In products containing the same concentrations of NaCl and sucrose, proteolytic activities decreased with an increase in ethanol concentration. At the same level of ethanol (7.5% or 15%), protein hydrolysis was highest in products containing 12.5% sucrose and 0% NaCl and lowest in products containing 0% sucrose and 12.5% NaCl. NaCl enhanced and sucrose reduced the effects of ethanol on inhibition of koji proteases. A salt-free fermentation was achieved using 15% ethanol and 12.5% sucrose. When sucrose (12.5%) was substituted by glucose, fructose, sorbitol, or glycerol and supplemented with 15% ethanol, prevention of protease inactivation by ethanol was similar to that with sucrose.     

Surimi Production from Partially Processed and Frozen Pacific Whiting (Merluccius productus)

Pacific whiting surimi was made from stabilized mince (SM), unstabilized mince (UM), and headed and gutted (H&G) fish kept in frozen storage and compared to a surimi control made from fresh fillets. SM was made by mixing fresh mince with 12% w/w sucrose and 0.2% w/w polyphosphates. Surimi was produced from SM, UM, H&G at 1, 30, 90, and 180 days and evaluated by torsion, measuring shear stress, and true strain. After 6 months, there were no differences (p>0.05) between surimi samples prepared from SM stored at - 20° and -50° and the control surimi. UM and H&G fish produced surimi of inferior quality.     

两种抗冻剂对罗非鱼鱼糜的凝胶性及抗冻性的影响

以凝胶性能、盐溶性蛋白含量及肌原纤维蛋白Ca2+-ATPase活性的变化为指标,研究了商业抗冻剂(蔗糖/山梨醇)和海藻糖在罗非鱼鱼糜冻藏过程中对蛋白质变性的影响。结果表明,冷藏20周后,添加8%商业抗冻剂和8%海藻糖组鱼糜的破断强度分别比对照高出39.14%和601.11%,凹陷强度分别比对照高出34.14%和39.85%,凝胶强度分别比对照高出36.03%和41.05%,盐溶性蛋白含量分别比对照高出30.00%和38.86%,肌原纤维蛋白Ca2+-ATPase活性分别为下降了67.12%和57.89%,而对照的肌原纤维蛋白Ca2+-ATPase没有活性。结论:添加8%海藻糖比8%商业抗冻剂更能有效抑制罗非鱼鱼糜在冻藏过程中的蛋白质变性,减缓凝胶强度的降低,提高鱼糜制品的质量。     

Cryoprotectant Effects during Short Time Frozen Storage of Chicken Myofibrillar Protein Isolates

The purpose of our study was to determine whether stabilization of myofibrillar protein isolates (MPI) during frozen storage could be achieved by addition of certain cryoprotectants. For 2–4 wk at - 21°C MPI were exposed to different freezing and thawing treatments to also determine to what extent cryoprotectants may prevent denaturation of MPI. Overall evaluation of color, weight losses of gels during cooking as well as texture proved that 2.8% sorbitol in combination with 4% starch was the best cryoprotectant. A positive effect was also noted for a mixture of 2.8% sorbitol and 4% sucrose. In contrast, the addition of a dextrose polymer mixture to MPI was not effective in maintaining product integrity.