Developing practical and small-scale radio frequency technology for tempering minced chicken breast at home

Radio frequency (RF) tempering, as a new tempering method suitable for overall heating applications, has been widely used for meat processing industry. However, an effective and uniform tempering process in a suitable RF system is still lacking for household applications. The cylindrical chicken breasts (Φ75 mm × 60 mm, Φ100 mm × 60 mm, and Φ125 mm × 60 mm) in a cubic polypropylene container were tempered in a newly self-built small-scale 50 Ω domestic RF heating system. Crushed ice was applied to surround the medium-size sample to improve the temperature distribution by matching the electric field behaviors in the RF tempering process. This study explored the effects of crushed ice assisted RF tempering (CIRFT) on heating behavior of test samples under three input power levels (300, 500, and 700 W) and three electrode gaps (80, 90, and 100 mm). The tempering performance between CIRFT and crushed ice assisted microwave tempering (CIMWT) were compared. The product quality [drip loss, color, pH value, and total volatile base nitrogen (TVBN) content] obtained through CIRFT, RFT, CIMWT, and MWT were compared. Results demonstrated that at the optimum CIRFT condition (500 W, 80 mm) the tempering rate and the heating uniformity of samples were improved as compared to RFT. In addition, the drip loss and TVBN content of the samples were relatively better with CIRFT than with RFT. Moreover, the better-quality attributes were obtained in RF treatments compared to MW tempering. Thus, CIRFT showed a positive effect on chicken tempering for household applications resulting in a rapid and uniform heating with a relatively greater retention of product quality.     

Effect of ferulic acid on inhibition of polyphenoloxidase and quality changes of Pacific white shrimp (Litopenaeus vannamei) during iced storage

Effects of ferulic acid (FA) on polyphenoloxidase (PPO) and the quality changes of Pacific white shrimp (Litopenaeus vannamei) during iced storage for 10 days were investigated. Both FA and oxygenated FA (OFA) with different concentrations (0.1%, 0.5%, 1% and 2% (w/v)) showed PPO inhibitory activity in a dose dependent manner. FA was generally more effective in PPO inhibition than was OFA. Based on activity staining, white shrimp PPO with an apparent molecular weight of 210 kDa was inhibited by FA. When whole shrimps were treated with FA solution with concentrations of 1% or 2% and stored in ice for up to 10 days, the increase in psychrophilic and mesophilic bacterial count were retarded, in comparison with the control and those treated with 1.25% sodium metabisulphite (SMS). The coincidental lower rates of increase in pH and total volatile base content were obtained. Additionally, shrimps treated with 2% FA possessed the lowest peroxide value and thiobarbituric acid reactive substances (TBARS) value during the storage. After 10 days of storage, shrimps treated with 2% FA had the lower melanosis score and higher score for colour, flavour and overall likeness, compared with the control and SMS treated shrimps (P < 0.05).     

Inhibition of melanosis formation in Pacific white shrimp by the extract of lead (Leucaena leucocephala) seed

Lead (Leucaena leucocephala) seed extract was prepared using distilled water as a medium. An extraction yield of 26.16 g/100 g of seed was obtained after extraction at room temperature for 12 h. Total phenolic and mimosine contents in the lead seed extract powder (LSEP) were 17.4 g GAE/100 g and 8.8 g/100 g, respectively. LSEP at different concentrations (0.05%, 0.1%, 0.25%, 0.5%, and 1%, w/v) showed inhibitory activity towards polyphenoloxidase (PPO) of Pacific white shrimp in a dose dependent manner. When the whole Pacific white shrimp were treated with 0.25% and 0.5% (w/v) LSEP, the shrimp treated with 0.5% LSEP had the lower melanosis score throughout the storage of 12 days and showed a higher score for colour and odour, as well as overall likeness, compared with the control (without treatment) and 1.25% sodium metabisulphite treated samples at day 12 (P < 0.05). Meat of shrimps treated with LSEP at both levels had the increase in mimosine content up to 8 days, suggesting the migration of mimosine into shrimp muscle during extended storage. Therefore, 0.5% LSEP can be used as a novel melanosis inhibitor for Pacific white shrimp.     

The effect of heating conditions on polyphenol oxidase, proteases and melanosis in pre-cooked Pacific white shrimp during refrigerated storage

Pre-cooked Pacific white shrimp (Litopenaeus vannamei) is an important shrimp product. However melanosis, especially in the cephalothorax including carapace and internal organs, is more likely caused by the remaining polyphenol oxidase (PPO) after pre-cooking. Thus, PPO from carapace and proteases from hepatopancreas of Pacific white shrimp were characterised and the remaining activities of both enzymes were monitored in pre-cooked shrimp during storage at 4 °C. Based on activity staining using L-β-(3,4 dihydroxylphenyl) alanine as a substrate, PPO consisted of two isoforms with apparent molecular weight of 210 and 220 kDa. No difference in activity band was observed when analysed under reducing and non-reducing condition. Proteases from hepatopancreas were able to activate PPO to some degree. For the in vitro study, both enzymes were quite stable when heated at temperature up to 70 °C but the loss in activities increased with increasing heating time (0-120 s). When Pacific white shrimp were pre-cooked to obtain different core temperatures (50-90 °C), different PPO and protease activities were retained. Higher core temperatures were associated with lower PPO and protease activities, but higher cooking loss. When the shrimp were pre-cooked at 80 °C, the residual PPO and protease activities were 3.9% and 5.4%, respectively and cooking yield of 95.6% was obtained. The resulting pre-cooked shrimp possessed lower melanosis score during 7 days of storage at 4 °C. Thus, pre-cooking of shrimp to obtain a core temperature of 80 °C, with a holding time of 30 s, could prevent the severe cooking loss and lower melanosis during subsequent storage.     

Radio frequency tempering multiple layers of frozen tilapia fillets: the temperature distribution,energy consumption,and quality

Tempering is an important step for the seafood processing industry. Selecting an appropriate tempering method can optimize the quality of tilapia. Volumetric radio frequency heating is able to compete tempering within minutes regardless product sizes. Twelve pieces of frozen tilapia fillets in four layers were used as target samples for a radio frequency tempering study. To improve the tempering uniformity, a thin layer of polyurethane foam was applied in-between layers. The present study explored the optimum radio frequency (RF) tempering processing parameters including three input powers (600, 800, 1000 W) and three electrode gaps (10, 12, 14 cm), batch and continuous mode, and compared it to water-tempering effects on the temperature distribution, drip loss, color, TBARS and texture of tilapia. Results demonstrated that the temperature distribution of tilapia with the optimum RF tempering condition (800 W, 12 cm) was more uniform than water tempering, and the TBARS value of samples tempered by RF is lower than that of water tempering. RF-tempering processes retained the L* value (58.76) and a* value (6.54) of tilapia samples, and also resulted in the highest hardness at 298.59 g. Most of the texture indexes of the tempered tilapia fish show no significant difference (p > 0.05) among all tempering conditions. Thus, RF shows a great potential in fish-tempering industry with its fast, uniform and controllable characteristics and a better retention of fish quality     

Application of ergothioneine-rich extract from an edible mushroom Flammulina velutipes for melanosis prevention in shrimp,Penaeus monodon and Litopenaeus vannamei

This report investigated the melanosis-inhibiting properties of crude water soluble extract from the base and fruiting body waste of an edible mushroom (Flammulina velutipes) containing 9.13 ± 2.03 mg/mL 2-thiol-l-histidine-betaine (ergothioneine, ESH). Immersion of live full-grown black tiger shrimp (Penaeus monodon) and Pacific white shrimp (Litopenaeus vannamei) in a 0.5% w/v solution of mushroom extract for 1 h significantly decreased polyphenoloxidase (PPO) activity in shrimp hemolymph and expression of the prophenoloxidase (proPO) gene in hemocytes. Consequently, the development of melanosis in the treated shrimp during ice storage was prevented. Treatment with a 0.05% w/v solution of sodium sulfite and 4-hexyl-1,3-benzenediol had a similar effect. Enzyme assays showed that ESH is a non-competitive inhibitor. It is proposed that ESH possibly interacts directly with Cu²⁺ at the putative binding sites of PPO and proPO, based on copper-chelating activity analyses, thus preventing melanosis in the shrimp. This study indicated that application of ESH-rich F. velutipes mushroom extract from trimming waste is an effective natural alternative to synthetic melanosis-inhibiting agents to prevent postmortem melanosis in shrimp.     

The effect of high-pressure treatment on functional components of shrimp (Litopenaeus vannamei) cephalothorax

High-pressure (HP) technology has been applied to extend the shelf life of shrimps by inhibiting enzymes with PPO activity or microorganisms. However, there is very little information on its effect on relevant compounds from a nutritional or functional point of view, such as fatty acids, α-tocopherol, astaxanthin, and hemocyanin, which constitutes the main objective of the present work. Shrimp cephalothoraxes were HP processed at 200, 400, or 600 MPa/18 °C/15 min or three consecutive 5 min cycles. It was found that hemocyanin was partially denatured at pressures up to 400 MPa, resulting in lower PPO activity, and it was totally denatured at 600 MPa, although 20% residual PPO activity remained. Astaxanthin, α-tocopherol, and total antioxidant activity were stable whichever HP treatment was applied, whereas 600 MPa caused a slight reduction of eicosapentaenoic acid (C20:5n3, EPA) and docosahexaenoic acid (C22:6n3, DHA). Despite this reduction, the ω-6/ω-3 fatty acids ratio was very low (1).Industrial relevanceShrimps are high-value fishery products with a very short shelf life under refrigeration, mainly because of microbial growth and development of melanosis. Thermal treatment is effective for extending shelf life, but it affects the nutritional quality of shrimps through degradation of bioactives such as polyunsaturated fatty acids, tocopherols, or astaxanthin, which are mainly located in the cephalothorax. High pressure is a non-thermal processing technology that has been proved to extend shrimp shelf life, but very little information can be found on its effect on the above-mentioned compounds as well as on the melanosis-inducing hemocyanin. Such basic knowledge is very important for industrial application of high-pressure technology to extend the shelf life of shrimps.     

Inhibition kinetics of catechin and ferulic acid on polyphenoloxidase from cephalothorax of Pacific white shrimp (Litopenaeus vannamei)

Inhibition kinetics and mode of catechin and ferulic acid towards polyphenoloxidase (PPO) from cephalothorax of Pacific white shrimp were investigated. Catechin or ferulic acid inhibited quinone formation catalysed by PPO in a dose dependent manner. Catechin showed mixed type reversible inhibition with K_i value of 1.4 mM, whereas ferulic acid exhibited non-competitive reversible inhibition with K_i value of 37 mM. With increasing concentrations, both catechin and ferulic acid had higher copper (Cu²⁺) reduction and copper chelating capacity (P < 0.05). Catechin or ferulic acid could react with intermediated browning reaction products, thereby preventing dopachrome formation. Thus, catechin or ferulic acid could inhibit melanosis in Pacific white shrimp with different modes of inhibition towards PPO.     

冰温技术结合保鲜剂对南美白对虾品质的影响

研究冰温技术结合4- 己基间苯二酚(4-hexylresorcinol,4-HR)等保鲜剂对延缓虾类黑变和保持品质方面的效果。通过正交试验确定保鲜剂的配方(M),以冻结试验确定冰温贮藏温度,测定贮藏设备的温控范围,通过评定南美白对虾的黑变感官得分,测定多酚氧化酶(PPO)活力、挥发性盐基氮(TVB-N)、pH 值和菌落总数(TBC)等鲜度指标评价保鲜效果差异。结果表明：南美白对虾的冰温带为－ 2.2～0℃,贮藏设备温度波动满足冰温技术要求,M 保鲜剂配方为0.01% 4- 己基间苯二酚+1.5% 柠檬酸+1% 抗坏血酸,冰温能显著减缓TVB-N 值、pH 值和TBC值增加速度,M 配方保鲜剂能有效抑制虾的多酚氧化酶活性和黑变,冰温技术结合M 配方保鲜剂保藏南美白对虾能互补二者优缺点,能显著减低黑变感官得分,PPO 活性、TVB-N、pH 值和TBC 的增长速度。比(4 ± 1)℃冷藏的货架期延长近1 倍。冰温技术结合保鲜剂能有效防止虾类黑变和延长品质货架期。     

微冻对南美白对虾质构的影响

以南美白对虾为对象,研究了其在-3℃微冻条件下质构参数(硬度、弹性、剪切力,咀嚼性、黏附性、胶黏性)的变化,同时考察了TVBN值、汁液流失率和感官特性的变化。结果表明:随着贮藏时间的延长,TVBN和汁液流失率均呈上升趋势;在贮藏至第14天以前,硬度、弹性、剪切力、咀嚼性呈上升趋势,之后逐渐下降,而黏附性一直呈现上升趋势,胶黏性呈下降趋势;结合TVBN值、汁液流失率和感官特性测定结果,南美白对虾质构测定结果能够较客观的表现其品质。     

Effect of cinnamaldehyde on melanosis and spoilage of Pacific white shrimp (Litopenaeus vannamei) during storage

BACKGROUND: Shrimp is a very perishable product and postmortem changes occur rapidly. Sulfiting agents were once and are still widely used as a preservative in the shrimp industry. However, the application of sulfite in shrimp may pose a risk to human health. Thus development of a natural preservative as a sulfite alternative to extend the shelf life of Pacific white shrimp is urgently needed. RESULTS: The effects of cinnamaldehyde essential oil (1 and 5 g kg^?1) on the shelf life of Pacific white shrimp stored at 4 °C were investigated. As the concentration of cinnamaldehyde increased, residual polyphenoloxidase (PPO) enzyme activity decreased. Kinetic analysis showed that cinnamaldehyde was a noncompetitive inhibitor for the oxidation of L ‐DOPA (L ‐3,4‐dihydroxyphenylalanine) by PPO of Pacific white shrimp. Based on this study, shrimp treated with 5 g kg^?1 cinnamaldehyde possessed the lowest aerobic plate count, total volatile basic nitrogen, and pH values in all treatments after 10 days of storage. According to the results of L*, cinnamaldehyde showed inhibitory activity toward the formation of melanosis. CONCLUSION: Treatment with cinnamaldehyde could improve the sensory properties and extend the shelf life of Pacific white shrimp to 8 days. Therefore, cinnamaldehyde could be used as a promising natural preservative for inhibiting melanosis and preventing the growth of microbes during the chilled storage of Pacific white shrimp. Copyright © 2012 Society of Chemical Industry     

Effect of Green Tea Extract in Combination with Ascorbic Acid on the Retardation of Melanosis and Quality Changes of Pacific White Shrimp During Iced Storage

Melanosis and quality changes of Pacific white shrimp (Litopenaeus vannamei) treated with 0.1% green tea extract (GTE) in combination with ascorbic acid (AA) at different levels (0%, 0.005%, and 0.01%) were monitored during iced storage of 12?days. Based on in vitro study, 0.1% GTE inhibited polyphenoloxidase (PPO) from cephalothorax of Pacific white shrimp by 60.2%. Nevertheless, 0.1% GTE in combination with 0.01% AA exhibited the greater PPO inhibitory activity (93.0%) (P?<?0.05). When shrimp treated with 0.1% GTE in combination with AA (0.005 or 0.01%; GTE + AA), the increase in psychrophilic bacteria and spoilage microorganisms including H₂S- producing bacteria and enterobacteriaceae were retarded to a higher extent, in comparison with the control and those treated with 1.25% sodium metabisulfite (SMS; P?<?0.05). The coincidental lowered rates of increase in pH, total volatile base content and thiobarbituric acid reactive substances were obtained in the shrimp treated with GTE + AA (P?<?0.05). Additionally, shrimp treated with GTE + AA had the lower melanosis score but higher score for color, odor, taste, flavor, and overall likeness, compared with the control and those treated with SMS (P?<?0.05). Generally, AA at levels of 0.005% and 0.01% showed a similar synergist effect with GTE on both melanosis inhibition as well as retardation of quality loss of shrimp.     

Quality and shelf life assessment of Pacific white shrimp (Litopenaeus vannamei) freshly harvested and stored on ice

Pacific white shrimps (Litopenaeus vannamei) are an important shrimp aquaculture species worldwide. To quantify the quality and shelf life of untreated shrimp is imperative prior to the application of preservative treatments. In this paper, the quality and shelf life of Pacific white shrimp freshly harvested from three different farms and stored on ice for up to 12 days was investigated. The titratable acidity (TA) of shrimp specimens exhibited significant decreases (P < 0.05) whereas the metric chroma (C), total colour difference (TCD), aerobic plate count (APC), trimethylamine (TMA-N) and total volatile basic – nitrogen (TVB-N), peroxide value (PV) and p-anisidine value (AnV) exhibited significant increases during iced storage (P < 0.05). The TMA-N and TVB-N were significantly correlated whereas temporal TMA-N/TVB-N ratio increased considerably (P < 0.05). While the PV and AnV significantly correlated (P < 0.05), the temporal PV/AnV ratio depicted how primary and secondary lipid oxidation of Pacific white shrimp could relate during iced storage of 12 days. The shelf life of ice stored Pacific white shrimps was determined to be 8 days. The information gained by this study could serve as baseline for preservative treatments applied to fresh shrimps.     

中华管鞭虾多酚氧化酶的分离制备

对中华管鞭虾中多酚氧化酶(PPO)的提取分离及其影响因素进行研究,讨论了新鲜管鞭虾的保藏温度、提取方法、浸提时间、缓冲液pH值、料液比和超声波提取等单因素影响,在此基础上采用正交法对各因素进一步优化。结果表明:在室温状态下,使用溶液浸提法,最佳时间为8h,最佳料液比为1:2,缓冲液最适pH值为8,超声时间为20min。     

Effect of pyrophosphate and 4-hexylresorcinol pretreatment on quality of refrigerated white shrimp (Litopenaeus vannamei) kept under modified atmosphere packaging

ABSTRACT:  The effect of pretreatment with pyrophosphate and 4-hexylresorcinol in combination with modified atmosphere packaging (MAP) (80% CO₂, 10% O₂, 10% N₂, or 80% CO₂, 20% N₂) on the quality of white shrimp during storage at 4 °C was investigated. Shrimp pretreated with 2% pyrophosphate and 0.25% 4-hexylresorcinol and stored under MAP showed the lower microbiological and chemical deteriorations as evidenced by delayed microbial growth as well as lower trimethylamine (TMA) and total volatile base nitrogen (TVB) production ( P < 0.05). Additionally, the growth of coliforms was inhibited effectively. White shrimp pretreated with 4-hexylresorcinol had the lower melanosis throughout the storage compared with those without treatment ( P < 0.05). This was associated with the lowered polyphenol oxidase (PPO) activity in shrimp treated with 4-hexylresorcinol. Therefore, the effective retardation of microbiological and chemical deterioration of white shrimp stored under MAP with the decrease in melanosis could be achieved by pretreatment of the shrimp with pyrophosphate and 4-hexylresorcinol. Furthermore, decapitation could be another means to lower the microbial load and melanosis in white shrimp, particularly those stored under MAP.     

南美白对虾冰温气调保鲜效果评价

将鲜南美白对虾进行空气包装(AP)、真空包装(VP)、气调包装(MAP,75% CO2/25% N2),分别冰温(－2.3～0℃)贮藏和冰藏,通过研究样品贮藏过程中多酚氧化酶(PPO)活力、总挥发性盐基氮(TVB-N)、菌落总数(TPC)、汁液流失率(DL)的变化,结合感官指标评价冰温气调保鲜的效果。结果表明：南美白对虾的PPO活力变化与腐败变质同步;冰温结合MAP能有效防止褐变,货架期可达10d,比冰藏结合AP延长了约3倍,此时样品色泽良好,TPC、TVB-N、DL分别为5.4(lg(CFU/g))、25.6mg/100g、3.13%,而其他包装样品已腐败。VP也能较好的保持色泽,但贮藏后期汁液流失相对严重,影响外观。     

Comparative studies on the effect of the freeze–thawing process on the physicochemical properties and microstructures of black tiger shrimp (Penaeus monodon) and white shrimp (Penaeus vannamei) muscle

The effects of different freeze–thaw cycles (0, 1, 3 and 5) on the physicochemical properties and microstructures of black tiger shrimp (Penaeus monodon) and white shrimp (Penaeus vannamei) muscle were investigated. White shrimp had greater exudate loss and higher α-glucosidase (AG), as well as β-N-acetyl-glucosaminidase (NAG) activities, than did black tiger shrimp, especially when the number of freeze–thaw cycles increased (P < 0.05). The decreases in Ca²⁺-ATPase activity, sulfhydryl group content and protein solubility with concomitant increases in disulfide bond formation and surface hydrophobicity were more pronounced in white shrimp muscle, than in black tiger shrimp muscle, particularly after five cycles of freeze–thawing (P < 0.05). The shear force of both shrimps was decreased after five freeze–thaw cycles (P < 0.05). The microstructure study revealed that the muscle fibers were less attached, with the loss of Z-disks, after subjection to five freeze–thaw cycles. Therefore, the freeze–thawing process caused denaturation of proteins, cell disruption, as well as structural damage of muscle in both shrimps. White shrimp generally underwent physicochemical changes induced by the freeze–thawing process to a greater extent than did black tiger shrimp.     

Sulfur-Containing Compounds Heated under Alkaline Condition: Antibrowning, Antioxidative Activities, and Their Effect on Quality of Shrimp during Iced Storage

ABSTRACT:  Sulfur-containing compounds heated under alkaline condition (pH 10) were determined for inhibitory activity toward polyphenol oxidase (PPO) from Pacific white shrimp ( Litopenaeus vannamei ) and for antioxidative activity. Cysteine and glutathione (GSH) (20 mM) heated at 100 °C at pH 10 strongly inhibited PPO activity. Heated alkaline cysteine showed the greater 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging activity, copper-chelating activity and reducing power than cysteine and glucose–cysteine Maillard reaction products ( P  < 0.05). Effect of heated alkaline cysteine at different concentrations (0, 20, and 100 mM) on the quality changes of Pacific white shrimp during iced storage was investigated. Shrimp treated with 100 mM heated alkaline cysteine had the lowest melanosis score, thiobarbituric acid-reactive substances (TBARS) value and total viable count (TVC), compared with those without treatment and treated with 20 mM heated alkaline cysteine, throughout the storage of 12 d ( P  < 0.05). Therefore, heated alkaline cysteine can be used as a novel additive to retard melanosis and extend the quality of postmortem shrimp.     

Comparison of microwave-assisted induction heating system (MAIH) and individual heating methods on the quality of pre-packaged white shrimp

Microwave-assisted induction heating (MAIH) is a novel heating technology that combines microwave heating in the upper section and induction heating at the bottom. Our previous study demonstrated that optimal cooking in white shrimp can be achieved by MAIH either at 130 °C for 80 s or at 90 °C for 100 s. The objective of this study was to compare the cooking of white shrimp using microwave heating or induction heating alone with that using MAIH under the optimum cooking condition. The following three methods for cooking white shrimp were analyzed: (1) induction heating (IH) at 90 °C for 100 s or at 130 °C for 80 s; (2) microwave heating (MW) at 1300 W and 2450 MHz for 80 or 100 s; and (3) MAIH at 90 °C for 100 s or at 130 °C for 80 s. The results showed that using only induction or microwave heating gave the shrimp an uncooked or undercooked appearance; meanwhile, cold spots and non-uniform temperature distribution were observed in the thermal image of the shrimp. On the contrary, the shrimps processed by MAIH were found to be fully cooked, and a uniform temperature distribution was observed in the corresponding thermal image. Furthermore, no detectable aerobic plate count (APC), psychrophilic bacteria count (PBC), and coliform were found in the shrimp samples processed by MAIH. The color (L*, a*, b*, W, and ΔE), hardness, cohesiveness and chewiness of the samples processed by MAIH were all significantly greater (p < 0.05) than those of shrimp processed by induction or microwave heating alone, indicating that MAIH cooking shrimp exhibited better color and texture than MW or IH alone. The results showed that the shrimps heated with MAIH at both 130 °C or 90 °C had better microbiological, physical and chemical quality, as compared to MW or IH heating alone.Industrial relevanceThis novel MAIH technology allows shrimp to be heated and pasteurized after being packed, thereby eliminating the post-pollution issue. Therefore, it has a great potential for developing short-time in-package pasteurization processes in food industry.     

Controlled atmosphere as coadjuvant to chilled storage for prevention of melanosis in shrimps (<Emphasis Type="Italic">Parapenaeus longirostris</Emphasis>)

The effect of a controlled atmosphere with high CO₂ and low O₂ levels on melanosis in deepwater pink shrimps (Parapenaeus longirostris) treated with sulphites was studied in samples in chilled storage. The application of atmosphere in shrimps without antimelanotics did not inhibit melanosis. Shrimps treated with 4% sulphites in combination with a concentration of 53% CO₂ and 7% O₂ totally inhibited darkening during storage. Covering with crushed ice produced an undesirable shrinking of muscle shrimp after cooking. The application of lower concentrations of CO₂ (45%) reduced the effectiveness in preventing darkening, compared with 53% CO₂, except where the melanosis inhibitor was 4-hexylresorcinol (0.1%). The residual effect of the gas when the shrimps were kept in a controlled atmosphere for 24 h was insufficient to prevent melanosis during further cold storage.