Kongkarn Kijroongrojana

Properties, translucence, and microstructure of Pacific white shrimp treated with mixed phosphates as affected by freshness and deveining.

Effects of freshness and deveining on some properties, translucence, and microstructure of Pacific white shrimp (Litopenaeus vannamei) soaked in 2.5% NaCl containing different phosphates were studied. Shrimp soaked in all solutions had increases in weight gain and cooking yield with lowered cooking loss, compared with the control (P < 0.05). However, efficacy of mixed phosphates in quality improvement of ice-stored shrimp was lower than fresh shrimp. Deveining resulted in increased weight gain and yield (P < 0.05). Nevertheless, samples treated with phosphates became more translucent. Shrimp stored in ice for 7 d and treated with mixed phosphates were generally more translucent than fresh counterparts (P < 0.05). Shrimp soaked in 2.5% NaCl containing 0.875% sodium acid pyrophosphate (SAPP) and 2.625% tetrasodium pyrophosphate (TSPP) were generally less translucent and had high weight gain and cooking yield along with low cooking loss. The microstructure study revealed that the muscle fibers were less attached with the loss of Z-disks after being treated with mixed phosphates. Cooked meats of fresh shrimp and ice-stored shrimp had more compact fiber arrangement with the shrinkage of sarcomere compared with raw samples. Disintegration was observed at the M-line in ice-stored shrimp treated with mixed phosphates after cooking, while such a phenomenon was not found in the cooked fresh sample treated with phosphates. T(max) and enthalpy of both myosin and actin peaks shifted to lower values when shrimp were treated with mixed phosphates (P < 0.05). Those changes were generally more pronounced in ice-stored shrimp. Therefore, freshness and deveining process had an impact on the quality of Pacific white shrimp treated with phosphates.

Autolysis of Pacific White Shrimp (Litopenaeus vannamei) Meat: Characterization and the Effects of Protein Additives

Autolytic activity of Pacific white shrimp (Litopenaeus vannamei) mince in the absence and in the presence of 2.5%NaCl was investigated. Pacific white shrimp mince exhibited the maximum autolytic activity at 35 and 40 degrees C in the absence and in the presence of 2.5%NaCl, respectively, as evidenced by the highest TCA-soluble peptide content and the greatest disappearance of myosin heavy chain (MHC). The autolysis was more pronounced in the acidic pH values, followed by alkaline pH ranges. Pepstatin A showed the highest inhibition toward autolysis in the acidic condition, revealing that aspartic proteinase was dominant in shrimp muscle. Nevertheless, soybean trypsin inhibitor effectively inhibited the autolysis at neutral and alkaline pH values, suggesting that serine proteinase was present in shrimp mince but contributed to autolysis at a lower extent in shrimp meat. Autolysis in shrimp meat could be inhibited partially by all protein additives, including bovine plasma protein (BPP), egg white (EW), and whey protein concentrate (WPC). The inhibition of autolysis increased when the level of protein additives increased with the concomitant increase in band intensity of MHC retained. WPC and BPP in the range of 2% to 3% exhibited the highest inhibition toward autolysis of shrimp mince.

Effect of high pressure and heat treatments on black tiger shrimp (Penaeus monodon Fabricius) muscle protein

Application of high pressure, a minimal processing, has gained interest particularly in extending the shelf-life or modifying the texture of seafood, especially in shrimp. However, pressurization may render the products with different texture as compared with their fresh and heated counterparts. Therefore, the impact of high-pressure treatment (200, 400, 600, and 800 MPa for 20 min at 28°C) on black tiger shrimp muscle proteins in comparison with heat treatment (100°C for 2 min) was investigated. Differential scanning calorimetry thermogram indicated that high pressure up to 200 MPa for 20 min induced the denaturation of myosin and actin with subsequent formation of a network stabilized by hydrogen bond. An electrophoretic study revealed that the sample pressurized at 800 MPa or heated at 100°C was also stabilized by disulfide bond. L*, a*, and b* values, compression force, and shear force increased with increasing pressure (p < 0.05). The heat-treated sample had higher L*, a*, b*, and shear force (toughening) than the pressurized and fresh samples (p < 0.05). Pressure at different levels had no effect on weight loss (p ≥ 0.05). However, a weight loss of 27.89% was observed in the heat-treated sample. Proteolytic activity of crude extract from the pressurized sample at 200 to 600 MPa did not differ from that of the fresh sample (p < 0.05). Nevertheless, the activity in the heated sample and that of the pressurized sample at 800 MPa decreased, indicating the inactivation of endogenous proteases in the muscle.

Effect of pre-cooking times on enzymes, properties, and melanosis of Pacific white shrimp during refrigerated storage

Pre-cooked shrimp have gained interest due to their attractive color and flavor. However, shrimp without sufficient pre-cooking have faced melanosis, particularly during the extended storage. This leads to the rejection by consumers and the market. Therefore, pre-cooking with appropriate time would be a means to tackle such a problem. The objective of this study was to investigate the effect of pre-cooking times on enzyme activities, properties, microstructure, and melanosis of Pacific white shrimp (Litopenaeus vannamei). Pacific white shrimp were subjected to pre-cooking at 80°C for various times (0 to 120 s). The residual activities of polyphenoloxidase (PPO) and protease decreased with increasing pre-cooking times (p < 0.05). Nevertheless, the increasing pre-cooking time resulted in more cooking loss. With cooking time above 60 s, a cooking loss of 9.85% was obtained (p < 0.05). Marked decreases in the relative PPO and protease activities were observed within the first 30 s of pre-cooking, and negligible activities were detected after 120 s. The microstructure study revealed that the muscle fibers of pre-cooked shrimps were less attached with concomitantly higher shrinkage of the sarcomere, compared with those of the raw counterpart. Shrimps pre-cooked with longer time showed a lower development of black spots as evidenced by a lower melanosis score throughout storage of 7 days at 4°C. Therefore, a pre-cooking time of 30 s at 80°C was sufficient to lower PPO and protease activities with the minimized cooking loss and melanosis during refrigerated storage.

Quality Indices of Squid (Photololigo duvaucelii) and Cuttlefish (Sepia aculeata) Stored in Ice

The objective quality indices of squid (Photololigo duvaucelii) and cuttlefish (Sepia aculeata) stored in ice were compared with the subjective counterparts. Sensory (overall quality rating, quality index method [QIM], and multisample difference test), microbiological (total viable count [TVC], psychrophilic count), chemical (trichloroacetic acid-soluble peptide [TCA-soluble peptide], trimethylamine nitrogen [TMA-N], total volatile bases nitrogen [TVB-N], ammonia content, and protein pattern), and physical analyses (expressible drip, color, and texture) were determined in both species during 16 days of iced storage. As storage time increased, TCA-soluble peptide, TVB, ammonia content, and expressible drip were increased (p < 0.05). TMA content was markedly increased after 10 and 8 days of storage in squid and cuttlefish, respectively. Both TVC and psychrophilic count increased as the storage time increased (p < 0.01). Myosin heavy chain was degraded with coincidental decrease in shear force and sensory texture during storage (p < 0.05). According to the overall rating score, shelf life of both species in ice was estimated to be 6 days. The increases in ammonia content and expressible drip were highly correlated with the decrease in overall quality rating and increase in quality index score of squid and cuttlefish (p < 0.01).

Effect of bovine and fish gelatin in combination with microbial transglutaminase on gel properties of threadfin bream surimi

Textural property of surimi products is a prime factor in determining the acceptability of consumer as well as market value. Gelatin is one of the most popular biopolymers widely used in food industry as gelling agent with the unique textural properties. Therefore, the addition of gelatin along with the use of protein cross-linkers could be a means to modify the texture of surimi gel, which can fit the demand of consumers. Surimi from the threadfin bream (Nemipterus bleekeri) was added with bovine gelatin (BG) and bovine/fish gelatin mix (BFGM; 1:1, 2:1, 1:2, 4:1, and 1:4) at 10% protein substitution in combination with and without microbial transglutaminase (MTGase) at 1.2 units/g surimi. Textural properties, whiteness, expressible moisture content, protein pattern, and microstructure and sensory properties of gels were determined. When MTGase at 1.2 units/g surimi was incorporated, the increases in breaking force and deformation were noticeable in both surimi gels, with and without 10% BG added ( p < 0.05). On the other hand, surimi gels added with BFGM at all bovine/fish gelatin ratios had the higher breaking force and deformation, compared with that added with BG, when MTGase was incorporated. Addition of BG or BFGM lowered the expressible moisture content and whiteness of surimi gel ( p < 0.05). Based on SDS-PAGE, band intensity of myosin heavy chain and actin of surimi gel decreased when surimi gel was added with all gelatins, regardless of MTGase addition. The microstructure study revealed that surimi gel network became finer and denser with the addition of MTGase (1.2 units/g surimi), but the coarser and irregular structure was obtained when gelatin was incorporated. Gelatin, especially bovine/fish gelatin mix, at an appropriate level could be used as the protein additive in surumi gel in conjunction with MTGase in order to improve the textural and nutritive properties of the products.

Perceived sensory quality of unpolished pigmented and milled white rices

The purpose of this paper is to explore and compare consumer perceptions of unpolished pigmented rice and milled white rice between unfamiliar and typical consumers.,This study first employed focus groups to explore attitudes and habits relating to rice consumption among British subjects. A sensory descriptive analysis method, flash profiling (FP), was then applied on consumer panels in the UK and Thailand to gain perceived sensory quality of unfamiliar and typical rice samples. The sensory profiles generated by British and Thai panellists were analysed by generalised procrustean analysis (GPA) and compared based on perceived attributes, dominant characteristics and repeatability.,Focus group results suggested that consumer familiarity with rice might influence preferred rice textural quality. The prominent textures of stickiness and bittiness of unpolished pigmented rice were negatively associated with perceived quality in the UK participants. The sensory profiles generated by GPA consisted of similarity with darkness of colour and sweet/earthy type odours that are key dominant characteristics of the Thai pigmented rice.,The research has provided sensory information of the unpolished pigmented rice as compared with milled white rice. The information gives insights on product development directions for export and further research on rice processing and cooking instructions.,This study is the first to apply sensory evaluation in a cross-cultural comparison of pigmented rice.

Influences of a natural colourant on colour and salty taste perception, liking, emotion and purchase intent: a case of mayonnaise-based dipping sauces

Summary Effects of colourant and a ‘natural source’ statement on sensory liking, emotion, saltiness expectation and purchase intent (PI) of three dipping sauces containing shrimp head colourant [no-colourant (NC); moderate-colourant (MC, 1.2% colourant); high-colourant (HC, 3.6% colourant)] were evaluated. Consumers disliked colour of HC compared to MC (4.65 vs. 6.24). Despite the same NaCl level, saltiness liking decreased with increasing colourant [6.38 (NC), 5.43 (MC), 3.97 (HC)]. Correspondence analysis biplot revealed that sauces with or without natural colourant were associated more with positive emotions. Positive emotion (good, interested, satisfied) scores decreased while negative emotion worried increased with increasing colourant concentration. The ‘natural source’ statement decreased guilty and unsafe scores but minimally affected PI of NC and MC. Saltiness expectation was not different between NC (off-white colour) vs. MC (lighter orange) and between NC vs. HC (darker orange); however, consumers expected HC to be saltier than MC.