Inhibition of Bacillus cereus spore outgrowth and multiplication by chitosan

Bacillus cereus is an endospore-forming bacterium able to cause food-associated illness. Different treatment processes are used in the food industry to reduce the number of spores and thereby the potential of foodborne disease. Chitosan is a polysaccharide with well-documented antibacterial activity towards vegetative cells. The activity against bacterial spores, spore germination and subsequent outgrowth and growth (the latter two events hereafter denoted (out)growth), however, is poorly documented. By using six different chitosans with defined macromolecular properties, we evaluated the effect of chitosan on Bacillus cereus spore germination and (out)growth using optical density assays and a dipicolinic acid release assay. (Out)growth was inhibited by chitosan, but germination was not. The action of chitosan was found to be concentration-dependent and also closely related to weight average molecular weight (M_w) and fraction of acetylation (F_A) of the biopolymer. Chitosans of low acetylation (F_A = 0.01 or 0.16) inhibited (out)growth more effectively than higher acetylated chitosans (F_A = 0.48). For the F_A = 0.16 chitosans with medium (56.8 kDa) and higher M_w (98.3 kDa), a better (out)growth inhibition was observed compared to low M_w (10.6 kDa) chitosan. The same trend was not evident with chitosans of 0.48 acetylation, where the difference in activity between the low (19.6 kDa) and high M_w (163.0 kDa) chitosans was only minor. In a spore test concentration corresponding to 10²-10³ CFU/ml (spore numbers relevant to food), less chitosan was needed to suppress (out)growth compared to higher spore numbers (equivalent to 10⁸ CFU/ml), as expected. No major differences in chitosan susceptibility between three different strains of B. cereus were detected. Our results contribute to a better understanding of chitosan activity towards bacterial spore germination and (out)growth.     

Physicochemical and functional properties of chitosans affected by sun drying time during decoloration

The typical production of chitosan from crustacean shell consists of demineralization, deproteinization, decoloration, and deacetylation. Selected physicochemical and functional properties of chitosans as affected by various decoloration times (4, 5, 6, 7 or 8 h) using sun drying were evaluated. Moisture content (6.67-6.89 g/100 g), degree of deacetylation (81.91-82.73%), and color L^∗ value (78.32-79.43) of chitosans were not affected by sun drying time. However, color a^∗ and b^∗ values decreased when sun drying time was over 4 h. The viscosity of chitosan solution (0.5 g/100 mL acetic acid) decreased gradually with increasing sun drying time, with a more pronounced effect observed at 8 h of sun drying. There was no change in water-binding capacity (WBC) of chitosans decolorized by sun drying between 4 and 6 h; however, further increase in sun drying time from 6 to 7 or 8 h increased WBC of chitosans. DPPH radical scavenging activity of chitosans increased with increasing sun drying time. This study demonstrated that white-colored chitosans could be produced by an alternative decoloration step using sun drying for 4 h following the deacetylation step. However, increasing sun drying time to 7 h produced chitosan with increased WBC and DPPH radical scavenging activity.     

Effect of molecular weight of chitosans on their antioxidative activities in apple juice

This work studies how chitosans with low molecular weight (LMWC, M_W = 12 kDa), medium molecular weight (MMWC, M_W = 95 kDa) and high molecular weight (HMWC, M_W = 318 kDa) affect antioxidant activity in an aqueous system and in apple juice. Antioxidant activity was determined, including that of DPPH radicals, hydrogen peroxide and superoxide anion radicals, as well as metal ion chelating capacity, ABTS radicals of chitosans with different molecular weights (DMWCs) in apple juice.     

Antioxidant potential of aroma compounds obtained by limonene biotransformation of orange essential oil

The antioxidant activities of a limonene biotransformation extract and of some standard monoterpenes present in the extract were assessed using four antioxidant assays: total antioxidant capacity, based on the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging assay, lipid peroxidation by the thiobarbituric acid (TBA) assay, superoxide anion release by cultured leukemic cells and glutathione S-transferase (GSTs) activity. The limonene biotransformation extract had free radical-scavenging activity (EC₅₀ = 2.09%, v/v) and inhibited lipid peroxidation (IC₅₀ = 0.13%, v/v). The extract, perillyl alcohol and α-terpineol inhibited lipid peroxidation by ∼80% at a concentration of 0.02% (v/v). Perillyl alcohol and α-terpineol also reduced the release of superoxide anions by cultured leukemic cells, by 3- and 10-fold, respectively, at concentrations of <0.02% (v/v). The biotransformation extract inhibited the conversion of nitrophenyl acetate to p-nitrophenol in the glutathione assay by ∼50%. These results indicate that, in addition to monoterpenes, other non-volatile compounds may contribute to the antioxidant activity of the biotransformation extract.     

The effects of different inorganic salts,buffer systems,and desalting of Varthemia crude water extract on DPPH radical scavenging activity

The DPPH radical-scavenging activity of 25 inorganic salts, two buffer systems, and crude water extract of aerial parts of Varthemia (Varthemia iphionoides) before and after resins purification were investigated. Eight of the 25 inorganic salts tested quenched the DPPH radical colour. Na₂S₂O₃ and FeCl₂ showed markedly high DPPH colour-quenching activity, with inhibition of 65.3% and 47.7% respectively, at a concentration of 10 μg/ml. Four salts slightly increased the intensity of DPPH radical colour. The rest of tested salts, acetate buffer, and phosphate buffer at a concentration less than 0.1 mM did not affect DPPH radical colour. The DPPH radical-scavenging activity of BHT and catechol was considerably affected by the concentration of phosphate buffer (pH 7.0), and by acetate buffer (pH 5.0) at concentrations more than 0.01 mM in the case of BHT only. The DPPH radical-scavenging activity of a crude water extract of aerial parts of Varthemia iphionoides was much higher than that of an extract desalted by cation-exchange resin, indicating that iron ions apparently elevated the DPPH radical-scavenging activity of the extract. Therefore, desalting of plant extracts is important in order to obtain the true value of DPPH radical-scavenging activity.     

Antioxidant and antimicrobial activities of Laetiporus sulphureus (Bull.) Murrill

Antioxidant capacity and antimicrobial activities of Laetiporus sulphureus (Bull.) Murrill. extracts obtained with ethanol were investigated in this study. The study was aimed at determining the antioxidant activity (DPPH free radical-scavenging, β-carotene/linoleic acid systems), total phenolic content and total flavonoid concentration of L. sulphureus. Inhibition values both of L. sulphureus ethanol and the standards increased parallel with the elevation of concentration in the linoleic acid system. Inhibition values of L. sulphureus (LS) extract, BHA and α-tocopherol standards were found to be 82.2%, 96.4% and 98.6%, respectively, at a concentration of 160 μg/ml. DPPH free radical-scavenging activity was found to exhibit 14%, 26%, 55% and 86% inhibition, respectively, at concentrations of 100, 200, 400 and 800 μg/ml. Total flavanoids were 14.2 ± 0.12 μg mg⁻¹ (quercetin equivalent) while the phenolics were 63.8 ± 0.25 μg mg⁻¹ (pyrocatechol equivalent) in the extract. Positive correlations were found between total phenolic content in the mushroom extracts and their antioxidant activities. Edible mushrooms may have potential as natural antioxidants. L. sulphureus showed narrow antibacterial activity against Gram-negative bacteria and strongly inhibited the growth of the Gram-positive bacteria tested. The crude extract exhibited high anticandidal activity on Candida albicans. Therefore, the extracts could be suitable as antimicrobial and antioxidative agents in the food industry.     

Antibacterial activity of chemically defined chitosans: influence of molecular weight, degree of acetylation and test organism

Chitosans, polysaccharides obtained from the exoskeleton of crustaceans, have been shown to exert antibacterial activity in vitro and their use as a food preservative is of growing interest. However, beyond a consensus that chitosan appears to disrupt the bacterial cell membrane, published data are inconsistent on the chemical characteristics that confer the antibacterial activity of chitosan. While most authors agree that the net charge density of the polymer (reflected in the fraction of positively charged amino groups at the C-2 position of the glucosamine unit) is an important factor in antibacterial activity, conflicting data have been reported on the effect of molecular weight and on the susceptibility among different bacterial species to chitosan. Therefore, we prepared batches of water-soluble hydrochloride salts of chitosans with weight average molecular weights (M_w) of 2-224 kDa and degree of acetylation of 0.16 and 0.48. Their antibacterial activity was evaluated using tube inhibition assays and membrane integrity assays (N-Phenyl-1-naphthylamine fluorescence and potassium release) against Bacillus cereus, Escherichia coli, Salmonella Typhimurium and three lipopolysaccharide mutants of E. coli and S. Typhimurium. Chitosans with lower degree of acetylation (F_A = 0.16) were more active than the more acetylated chitosans (F_A = 0.48). No trends in antibacterial action related to increasing or decreasing M_w were observed although one of the chitosans (M_w 28.4 kDa, F_A = 0.16) was more active than the other chitosans, inhibiting growth and permeabilizing the membrane of all the test strains included. The test strains varied in their susceptibility to the different chitosans with wild type S. Typhimurium more resistant than the wild type E. coli. Salmonellae lipopolysaccharide mutants were more susceptible than the matched wild type strain. Our results show that the chitosan preparation details are critically important in identifying the antibacterial features that target different test organisms.     

Bioprospecting traditional Pakistani medicinal plants for potent antioxidants

Antioxidant potential of four methanol extracts from three selected plant species, namely Salvia nubicola (Lamiaceae), Acer oblongifolium (Aceraceae) and Hedera nepalensis (Araliaceae) was measured using assays in aqueous and lipid systems. Antioxidant activities were investigated in aqueous systems by using DPPH radical-scavenging assay, ABTS radical-scavenging assay and DNA protection assay, while antioxidant activity in a lipid system was determined by using the thiobarbituric acid-reactive substances (TBARS) assay. Additionally, the Folin-Ciocalteu method was used to measure total phenolic content. Methanol extracts of leaves and flowers of S. nubicola showed the highest Trolox equivalent (TE) values in the case of the DPPH assay, 2484 ± 4.9 mmol TE/g extract, as well as total phenolic content, 139 ± 0.2 mg gallic acid equivalents/g extract. Three fractions (A-C) of the methanol extract of S. nubicola leaves and flowers were produced by semi-preparative HPLC. Fraction B was found to be the most active in the DPPH radical-scavenging assay and had the highest total phenol content. HPLC-DAD and LC-MS revealed rosmarinic acid in S. nubicola extracts and chlorogenic acid and rutin in H. nepalensis extracts as the main phenolic antioxidants.     

Coating citrus (Murcott tangor) fruit with low molecular weight chitosan increases postharvest quality and shelf life

This study investigates the effects of coating with low molecular weight chitosan (LMWC, Mw = 15 kDa) and high molecular weight chitosan (HMWC, Mw = 357 kDa) on the decay of Murcott tangor and the maintenance of its quality. A 0.1% LMWC coating substantially slowed the decay of Murcott tangor stored at 15 °C in relation to a control sample and reduced decay by over 20% as compared to the fungicide TBZ. A concentration of 0.2% LMWC was more effective in controlling the growth of fungus on citrus fruits caused by Penicillium digitatum and Penicillium italicum, exhibiting effective antifungal activity. LMWC coating improved firmness, titratable acidity, ascorbic acidity and the water content for Murcott tangor stored at 15 °C for 56 days. Consequently, Murcott tangor coated with LMWC exhibited greater antifungal resistance than TBZ and its quality was maintained for longer.     

Evaluation of the antioxidant activity of Ruellia tuberosa

The antioxidant activity of Ruellia tuberosa L. (Acanthaceae) was investigated by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging assay and the hydrogen peroxide-induced luminol chemiluminescence assay. The methanolic extract (ME) and its four fractions of water (WtF), ethyl acetate (EaF), chloroform (CfF), and n-hexane (HxF) were prepared and then subjected to antioxidant evaluation. The results of both methods revealed that R. tuberosa possesses potent antioxidant activity. The antioxidant activities of the different fractions tested decreased in the order of EaF > CfF > ME > WtF > HxF according to the hydrogen peroxide-induced luminol chemiluminescence assay, and results were the same with the exception of the rank order of HxF and WtF according to the DPPH free radical-scavenging assay. The results provide useful information on the pharmacological activities associated with free radicals of this traditional folk remedy.     

Enzymatic preparation of chitooligosaccharides by commercial lipase

The effect of a commercial lipase on chitosan degradation was investigated. When four chitosans with various degrees of deacetylation were used as substrates, the lipase showed higher optimal pH toward chitosan with higher DD (degree of deacetylation). The optimal temperature of the lipase was 55 °C for all chitosans. The enzyme exhibited higher activity to chitosans which were 82.8% and 73.2% deacetylated. Kinetics experiments show that chitosans with DD of 82.8% and 73.2% which resulted in lower K_m values had stronger affinity for the lipase. The chitosan hydrolysis carried out at 37 °C produced larger quantity of COS (chitooligosaccharides) than that at 55 °C when the reaction time was longer than 6 h, and COS yield of 24 h hydrolysis at 37 °C was 93.8%. Products analysis results demonstrate that the enzyme produced glucosamine and chitooligosaccharides with DP (degree of polymerization) of 2–6 and above, and it acted on chitosan in both exo- and endo-hydrolytic manner.     

Antioxidant constituents in feverfew (Tanacetum parthenium) extract and their chromatographic quantification

Medicinal herb feverfew (Tanacetum parthenium) has been reported to possess prophylactic properties over migraine and arthritis. However, less attention has been given to its antioxidant activities. In our study the antioxidant activities of the feverfew extract and its bioactive components in terms of their free radical-scavenging activities against the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and their Fe²⁺-chelating capacities were determined. In addition, the bioactive constituents in feverfew were determined by GC–MS and HPLC–UV. The results showed that feverfew powder extracted by 80% alcohol contained camphor, parthenolide, luteolin and apigenin in 0.30 ± 0.08%, 0.22% ± 0.03%, 0.84% ± 0.10% and 0.68% ± 0.07%, respectively. Total phenolic content of the feverfew extract was measured in 21.21 ± 2.11 μg gallic acid equivalent per mg dry material. The feverfew alcoholic extract possessed a strong DPPH free radical-scavenging activity of 84.4% and moderate Fe²⁺-chelating capacity of 53.1%. Luteolin also showed strong DPPH scavenging activity of approximately 80% at ? 0.52 mg/mL. Parthenolide exhibited weak DPPH scavenging activity of 15% and moderate Fe²⁺-chelating capacity of nearly 60%. Similar moderate Fe²⁺-chelating activity (approximately 60%) was observed for luteolin and apigenin at 2 mg/mL.     

Effect of microencapsulation on survival of Lactobacillus plantarum in simulated gastrointestinal conditions, refrigeration, and yogurt

In the present research the survival of free and microencapsulated cells of a new strain of Lactobacillus plantarum BL011 under stress conditions was tested in sodium alginate or pectin, coated with sodium alginate or chitosan. Results for the simulated gastrointestinal medium (SGT) showed no change in viability of cells in relation to the control. However, the simulated gastric medium (GM) drastically reduced the viability under the tested conditions, with no significant differences between free and immobilized cells. Under refrigerated storage viability of immobilized cells were greatly enhanced compared to the free microorganisms, and the treatments showing the lowest loss of viability were those of 4% (w/v) pectin, 3% (w/v) sodium alginate coated with chitosan and a mixture of 2% (w/v) sodium alginate and 2% (w/v) pectin, respectively. Loss of viability of immobilized L. plantarum in 3% alginate coated with chitosan in yogurt was of 0.55 log cycles during 38 days of storage. The results of this study suggest the efficiency of immobilization techniques to increase the survival of lactobacilli in yogurt under refrigerated storage.     

Screening of the antioxidative and antimicrobial properties of the essential oils of Pimpinella anisetum and Pimpinella flabellifolia from Turkey

The aerial parts of two endemic Pimpinella [Pimpinella anisetum Boiss. & Ball. and Pimpinella flabellifolia (Boiss.) Benth. ex Drude] were hydro-distilled to produce oils in the yields of 2.07% (v/w) and 2.61% (v/w), respectively. The oils were analysed by GC and GC/MS. Twenty-one and nineteen components were identified, representing 99.5% and 99.7% of the oils, respectively. The main compounds of P. anisetum were (E)-anethole (82.8%) and methyl chavicol (14.5%), whereas limonene (47.0%), (E)-anethole (37.9%) and α-pinene (6.0%) were the major constituents of P. flabellifolia. The oils were screened for their possible antioxidant activities by two complementary test systems, namely DPPH free radical-scavenging and β-carotene/linoleic acid systems. In the first case, P. anisetum oil exerted greater antioxidant activity than that of P. flabellifolia oil with an IC₅₀ value of 5.62 ± 1.34 μg/ml. In the β-carotene/linoleic acid test system, the oil of P. anisetum was superior to P. flabellifolia with 70.5% ± 2.86 inhibition rate. Essential oils of the plants studied here were also screened for their antimicrobial activities against six bacteria and two fungi. The oils showed moderate antimicrobial activity against all microorganisms tested.     

Effects on Salmonella shell contamination and trans-shell penetration of coating hens' eggs with chitosan

Chitosan is a biopolymer with antimicrobial activity and film-forming properties. In this study, the effects on Salmonella shell contamination and trans-shell penetration of coating hens' eggs with chitosan was evaluated. A chitosan was selected from eight types (four non-commercial and four commercial) based on its antimicrobial activity against Salmonella enterica serovar Enteritidis (S. Enteritidis). For this purpose, a contact plate method was developed and chitosans were applied at a concentration of 0.25% (w/v). A commercial type with a molecular weight of 310-375 kDa and a deacetylation degree of 75% that reduced S. Enteritidis by 0.71 log₁₀ colony forming units compared to the control (without chitosan) was selected for further studies. The chitosan was shown to have antimicrobial activity against other egg borne bacteria, i.e., Acinetobacter baumannii, Alcaligenes sp., Carnobacterium sp., Pseudomonas sp., Serratia marcescens and Staphylococcus warneri, and against S. enterica serovar Typhimurium, Escherichia coli and Listeria monocytogenes. The effects of various concentrations of the selected chitosan (0.25%, 1% and 2%) on Salmonella shell contamination and trans-shell penetration were assessed using the agar molding technique. Effective reduction of eggshell contamination could not be demonstrated, but trans-shell penetration was significantly reduced in the presence of a 2% chitosan eggshell coating, with only 6.1% of the eggs being penetrated compared to 24.5% of the uncoated eggs. It was concluded that the 2% chitosan coating has the potential to reduce contamination of egg contents resulting from trans-shell penetration by S. Enteritidis.     

Antioxidative activity of Rosmarinus officinalis L. essential oil compared to its main components

This study was designed to examine the in vitro antioxidant activities of Rosmarinus officinalis L. essential oil compared to three of its main components (1,8-cineole, α-pinene, β-pinene). GC–MS analysis of the essential oil resulted in the identification of 19 compounds, representing 97.97% of the oil, the major constituents of the oil were described as 1,8-cineole (27.23%), α-pinene (19.43%), camphor (14.26%), camphene (11.52%) and β-pinene (6.71%). The oil and the components were subjected to screening for their possible antioxidant activity by means of 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and β-carotene bleaching test. In the DPPH test system, free radical-scavenging activity of R. officinalis L. essential oil, 1,8-cineole, α-pinene and β-pinene were determined to be 62.45% ± 3.42%, 42.7% ± 2.5%, 45.61% ± 4.23% and 46.21% ± 2.24% (v/v), respectively. In the β-carotene bleaching test system, we tested series concentration of samples to show the antioxidant activities of the oil and its main components, whereas the concentrations providing 50% inhibition (IC₅₀) values of R. officinalis L. essential oil, 1,8-cineole, α-pinene and β-pinene were 2.04% ± 0.42%, 4.05% ± 0.65%, 2.28% ± 0.23% and 2.56% ± 0.16% (v/v), respectively. In general, R. officinalis L. essential oil showed greater activity than its components in both systems, and the antioxidant activities of all the tested samples were mostly related to their concentrations. Antioxidant activities of the synthetic antioxidant, ascorbic acid and BHT, were also determined in parallel experiments as positive control.     

Effect of chitosan-based solutions applied as edible coatings and water glazing on frozen salmon preservation – A pilot-scale study

The aim of this research was to compare the effect of chitosan solutions on frozen salmon preservation with that of water glazing. For this purpose, three chitosan solutions (0.25%, 0.50% and 0.75% w/v) and water were applied in different amounts (6%, 8% and 11% of coated fillet weight) directly on the surface of frozen salmon. In order to accelerate the deterioration processes, salmon was stored during 14 weeks at −5 °C. Microbial and chemical indices were used to assess deterioration during storage and the coating stability was evaluated through weight loss measurements. The results obtained showed that chitosan coatings can be a good barrier to protect frozen fish from deterioration. Microbial growth, assessed by total viable counts (TVC), and total volatile basic nitrogen (TVB-N) were maintained below the maximum limits recommended which are 5 × 105 CFU/g and 35 mg nitrogen/100 g fish, respectively. The use of 0.50% and 0.75% chitosan solutions generally demonstrated to be more efficient in preventing salmon weight loss.     

Antioxidant properties of peptide fractions from silver carp (Hypophthalmichthys molitrix) processing by-product protein hydrolysates evaluated by electron spin resonance spectrometry

Silver carp processing by-product protein is usually discarded as an industrial solid waste. In this study the protein was recovered using a pH-shift method, after which seven commercial proteases were separately employed to prepare antioxidative hydrolysates. Among the hydrolysates, pepsin hydrolysates, which had the highest free radical-scavenging activity, were further separated into five peptide fractions, SCPH-I (>10 kDa), SCPH-II (5–10 kDa), SCPH-III (3–5 kDa), SCPH-IV (1–3 kDa), and SCPH-V (<1 kDa), by using ultrafiltration. The antioxidative properties of the peptide fractions were investigated, using a free radical-scavenging assay, by electron spin resonance. The results show that SCPH-V had the highest scavenging effects on DPPH (1,1-diphenyl-2-picrylhydrazyl), hydroxyl and superoxide anion radicals. SCPH-V had potent antioxidant activity in the prevention of the peroxidation of linoleic acid and alleviation of H₂O₂-induced oxidative stress in human intestinal epithelial caco-2 cells. The results indicated that the antioxidant capacity of silver carp by-product hydrolysates could be enhanced by ultrafiltration.     

The antioxidative properties of mustard leaf (Brassica juncea) kimchi extracts on refrigerated raw ground pork meat against lipid oxidation

The efficacy of varying concentration of mustard leaf kimchi ethanolic extracts (MK) in retarding oxidative rancidity was tested with raw ground pork. Freshly ground pork meat was assigned to one of the following five treatments: control (no antioxidants); AC-0.02 (0.02% ascorbic acid); MK-0.05, 0.1, and 0.2 (0.05%, 0.1% and 0.2% MK, respectively). The pH of the samples decreased and the TBARS values and free fatty acids (%) increased considerably (P < 0.05) during storage. The total bacterial count was lower in MK-0.1 and MK-0.2 than the control during storage. The internal L∗ value and a∗ value decreased (P < 0.05) with the addition of MK. The internal b∗ value of MK treatments were higher (P < 0.05) than that for the control and increased incrementally with MK concentration. The TBARS values and free fatty acids (%) of MK-0.02 was lowest among the treatments. The peroxide value of the control increased until 7 days and reached the maximum value at a certain storage time and decreased thereafter. In the other treatments it increased. All treatments had lower concentration of conjugated dienes (P < 0.05) compared to the control sample, after the first day. Mustard leaf kimchi ethanolic extracts exhibited a protective effect against lipid oxidation in raw ground pork.     

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).