Reduction of Listeria monocytogenes in cold‐smoked salmon by bacteriophage P100, nisin and lauric arginate,singly or in combinations

Three GRAS antimicrobials including, lauric arginate (LAE), bacteriophage P100 (phage P100) and bacteriocin nisin, were evaluated either singly or in combinations for the reduction of initial load of Listeria monocytogenes in cold‐smoked salmon (CSS). The stability of phage P100 in the presence of LAE (200 ppm) and nisin (500 ppm) or at 10× and 100× of these concentrations was determined at 4 °C or 30 °C for 24 h in a broth model. Phage P100 was found to be highly stable in the presence of these antimicrobial agents as plaque‐forming units (PFU) did not vary between control and antimicrobial‐treated phage. The survival of L. monocytogenes in the presence of phage P100, nisin and LAE showed remarkable reduction within 24 h both at 4 °C or 30 °C in broth. Treatment of CSS containing 3.5 log CFU cm^?2 L. monocytogenes with phage P100 (10⁸ PFU mL^?1), nisin (500 ppm) and LAE (200 ppm) showed strong listericidal action and reduced the L. monocytogenes by 2–3 log CFU cm^?2 after 24 h. Among the combined treatments, phage P100 + LAE or nisin + LAE exhibited the most listericidal action in which L. monocytogenes cells were reduced to undetectable level within 24 h in CSS.     

Shelf life and quality of probiotic yogurt produced with Lactobacillus acidophilus and Gobdin

This study evaluated the effect of dry white mulberry and walnut paste (Gobdin, a traditional Turkish food) in probiotic yogurt on the survival of Lactobacillus acidophilus and yogurt properties. Six different yogurts were produced with 0%, 5% and 10% Gobdin using Lactobacillus bulgaricus + Streptococcus thermophilus and with 0%, 5% and 10% Gobdin using L. bulgaricus + S. thermophilus + L. acidophilus. The physical, chemical, microbiological and sensorial properties of the yogurts were evaluated based on storage at 4 ± 1 °C. Probiotic shelf life and the most suitable combinations were determined. The highest L. acidophilus count (8.65 log cfu g^?1) was found in the 5% Gobdin‐supplemented yogurt on the 7th day of storage, while the lowest count (8.11 log cfu g^?1) was found in the probiotic control yogurt on the 21st day. Although the L. acidophilus counts in the probiotic yogurts declined during storage, all values found throughout the 21‐day storage period were >8 log cfu g^?1. This is above the level necessary to provide the desired therapeutic effect in probiotic products (10⁶–10⁷ cfu g^?1). The highest overall acceptability score was obtained on the first day from the yogurt with 5% Gobdin. However, all yogurt samples had general acceptability scores between 7 and 8 points from a 9‐point maximum. Thus, this study determined that a new functional yogurt can be produced using L. acidophilus with 5% Gobdin.     

Antioxidative and antimicrobial activities of shrimp chitosan on gilthead sea bream (Sparus aurata) during refrigerated storage

This study aims to determine the effects of chitosan obtained from Metapenaeus stebbingi shells on the shelf life of refrigerated gilthead sea bream. It was determined that 1% chitosan‐coated samples had the lowest thiobarbituric acid (TBA) (3.05 mg malondialdehyde (MDA) kg^?1) and free fatty acids (FFA) value (2.79% oleic acid), while the control group had the highest TBA (5.08 mg MDA kg^?1) and FFA value (6.13% oleic acid) on the 27th day of storage. In the last day of storage, TVB‐N was found higher in control group (25.62 mg 100 g^?1) than chitosan‐coated samples (14.57 mg 100 g^?1). Total viable count value of the control group exceeded maximum permissible limit on the 27th day of storage. However, it was lower than 7.0 log CFU/g in chitosan‐coated samples during the refrigerated storage. As a result of this study, it was determined that shelf life of refrigerated gilthead sea bream can be increased up to 27 days with chitosan.     

Raffinose family oligosaccharides in seed of Glycine max cv. Chiang Mai60 and potential source of prebiotic substances

Raffinose family oligosaccharides (RFOs) content in Glycine max seed of cultivar Chiang Mai60, a local soybean of Thailand, was investigated. RFOs and other low molecular weight sugars were extracted by 50% (v/v) ethanol and quantified by high‐performance liquid chromatography (HPLC). The prebiotic property of this extract was subsequently studied by in vitro method. The results showed that the concentrations of raffinose, stachyose and verbascose were 6.74 ± 1.62, 145.32 ± 18.74 and 1.60 ± 0.52 mg g^?1 dry seed, respectively, while glucose and sucrose were detected at 10.73 ± 1.35 and 13.28 ± 2.16 mg g^?1 dry seed, respectively. The growth of four Lactobacilli probiotics were increased significantly in a basal liquid medium supplemented with this ethanolic extract as carbon source compared to glucose supplementation. Subsequently, defined mixed culture was studied and it was found that growth stimulation of total Lactobacilli by extracted sugars resulted in the suppression of Escherichia coli and Salmonella enterica serovar Typhimurium growth. It could be concluded that this cultivar showed the RFOs‐rich content and a potential to be a source of an effective prebiotic substance for food application.     

Antioxidant effects of rosemary extracts on sunflower oil compared with synthetic antioxidants

The antioxidant activities of ethanol extracts of rosemary (Rosmarinus officinalis L.) (RE) were tested in natural sunflower oil stored at 60 °C by measuring their peroxide values (POV), thiobarbituric acid‐reactive substances (TBARS), free fatty acid (FFA) content and p‐anisidine value (AnV) after regular intervals compared with synthetic antioxidants. After 3 weeks of storage at 60 °C, sunflower oil containing 200 mg kg^?1 rosemary extracts showed lower POVs (75.7 ± 0.47  meq kg^?1), thiobarbituric acid‐reactive substances (TBARS)(0.161 ± 0.002 μg mL^?1), FFA contents (0.45 ± 0.04 mg g^?1) and AnV (12.4 ± 0.02) than the control sample. Sunflower oil containing 200 ppm butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert‐butylhydroquinone (TBHQ) showed POVs (204 ± 0.68, 159 ± 0.55, 20 ± 0.49 meq kg^?1), thiobarbituric acid‐reactive substances (TBARS) (0.171 ± 0.002, 0.184 ± 0.002, 0.069 ± 0.001 μg mL^?1), FFA contents (0.34 ± 0.03, 0.46 ± 0.03, 0.2 ± 0.01 mg g^?1) and AnV (14.7 ± 0.03, 16.5 ± 0.04, 6.77 ± 0.01), respectively, after 3 weeks of storage at 60 °C. These results illustrate that rosemary extracts exhibited very strong antioxidant activity, almost equal to that of synthetic antioxidants (BHA and BHT).     

Effects of Pseudomonas chlororaphis and gaseous chlorine dioxide on the survival of Salmonella enterica on tomatoes

Control of Salmonella enterica on tomatoes is important for food safety. The aim of this research was to evaluate the survival of Salmonella enterica serovars Montevideo (SM) and Typhimurium (ST) on tomatoes exposed to gaseous chlorine dioxide and Pseudomonas chlororaphis (Pc). Pc was applied to stem scars of tomatoes prior to inoculations with SM and ST. Tomatoes were treated with gaseous ClO₂ at 0.4 mg L^?1 for 2 and 4 h (90% R.H. 13 °C), respectively. At 4 h of ClO₂ treatment, SM and ST populations were reduced to 0.82 and <0.30 log CFU g^?1, respectively. Tomatoes treated with SM and ST had 5.42 and 5.37 log CFU g^?1 of Salmonella. Tomatoes treated with Pc + Salmonella count was 2.59 (treated) and 5.83 log CFU g^?1 (control). Salmonella survival was similar at 2 and 4 h of ClO₂ treatment. Application of ClO₂ and Pc may reduce contamination of tomatoes by Salmonella serovars.     

Development and evaluation of chitosan and its derivative for the shelf life extension of beef meat under refrigeration storage

The current study was aimed to study the shelf life of beef meat at refrigeration storage using novel chitosan derivative (Ch‐D). Chitosan was modified with antimicrobial monomethyl fumaric acid (MFA). The chemical structure of the resulting material was characterized by FT‐IR and HR‐XRD. The results confirmed the successful synthesis of conjugate sample. For the shelf life study, following lots were used: control (distilled water), chitosan 0.5%, Ch‐D 0.5%. The samples were kept at 4 °C for 16 days and analyzed at 4‐day intervals. Ch‐D treatment significantly reduced the total viable counts, enterobacteriaceae, lactic acid bacteria, psychrotrophic bacteria, and yeasts–moulds when compared with the chitosan and control during refrigeration storage. The peroxide value (PV) for Ch‐D was 0.19 ± 0.04 meq O₂ kg^?1 fat and chitosan was 0.21 ± 0.07 meq O₂ kg^?1 fat and showed no significant difference (P < 0.05) at the end of the storage. Thiobarbituric acid reactive substance (TBARs) value for Ch‐D was 0.48 ± 0.02 mg MDA kg^?1 and chitosan was 0.57 ± 0.09 mg MDA kg^?1, while the carbonyl contents for Ch‐D was 3.16 ± 0.23 nm  mg^?1 protein and chitosan was 3.11 ± 0.16 nm  mg^?1 protein at 16 days of storage. Values for Ch‐D and chitosan treatments were significantly lower (P < 0.05) for all the quality attributes as compared with the control throughout storage. At the end of storage, Ch‐D treatment showed a significant increase (P < 0.05) in lightness (L^* = 41.54 ± 0.09) and yellowness (b* = 2.23 ± 0.04). The redness for control was high (a* = 6.12 ± 0.09) as compared with the treated samples. Based primarily on microbial counts, Ch‐D treatment extended the shelf life of beef meat by about 8 days, maintaining acceptable quality attributes.     

Preparation of alcalase hydrolysed rice bran protein concentrate and its inhibitory effect on soybean lipoxygenase activity

Rice bran protein concentrate (RBPC) was prepared from defatted rice bran and hydrolysed by alcalase at different hydrolysis times. As the hydrolysis times increased, the degree of hydrolysis (DHs) increased. RBPC hydrolysate obtained at 50 min (RBPCH‐50) had the highest inhibitory efficiency on soybean lipoxygenase (LOX) activity (66%). The inhibition kinetics of the reaction analysed by Lineweaver–Burk plots indicates that RBPCH‐50 is a competitive inhibitor. RBPCH‐50 inhibited soybean LOX with an IC₅₀ of 11.73 μg μL^?1 RBPCH‐50, and the obtained K_I was 4.59 μg μL^?1 RBPCH‐50. LOX inhibitory activity of RBPCH‐50 was significantly higher than that of 50 and 100 ppm butylated hydroxyanisole (BHA) and 50, 100, and 200 ppm butylated hydroxytoluene (BHT) (P ≤ 0.05); however, LOX inhibitory activity of RBPCH‐50 was similar to that of 200 ppm BHA (P > 0.05). Therefore, RBPCH might potentially be used as a natural LOX inhibitor.     

The impact of strawflower and mistletoe extract on quality properties of rainbow trout fillets

Many plants, including strawflower and mistletoe, contain antioxidants and antimicrobials, which can increase the shelf life of seafood. The main aim of this study was to investigate the effect of mistletoe and strawflower extracts at doses of 0.5% (w/v) on the sensory, chemical and microbiological properties of rainbow trout fillets during 27 days of storage at 2 ± 1 °C. The phenolic compounds in these plants have been studied, but their effects on food quality and storage properties have not been reported. We found that extract of mistletoe did not extend the shelf life of the fillets; however, the strawflower extract show high antimicrobial activity in fish fillets. The shelf life of rainbow trout was 20 days for the control and fish treated with mistletoe extract and 23 days for fish treated with strawflower extract. The antioxidant effect of extracts on fish fillets was weak, whereas strawflower extract had high antimicrobial effect. Peroxide value (PV) and thiobarbituric acid (TBA) values fluctuated during storage periods around main values below 14 meq O₂ kg^?1 and 0.6 MA kg^?1, respectively. Putrescine, cadaverine, spermine, spermidine, serotonin, tyramine and dopamine were main amine, whereas histamine accumulated at low levels (<2 mg per 100 g). Strawflower suppressed biogenic amine accumulation in fish fillets. At the limit of acceptability, total viable count (TVC), Enterobacteriaceae and lactic acid bacteria count remained below 7.6, 6.83 and 8.01 log CFU g^?1, respectively. The results of this study show that ethanol extracts of strawflower improve the shelf life of rainbow trout.     

Monitoring of free glutamic acid in Malaysian processed foods,dishes and condiments

A study to quantify the free glutamic acid content of six processed foods, 44 dishes and 26 condiments available in Malaysia was performed using high-performance liquid chromatography with a fluorescence detector (HPLC-FRD). Recovery tests were carried out with spiked samples at levels from 6 to 31 mg g^?1. High recovery in different matrices was achieved ranging from 88% ± 13% to 102% ± 5.12%, with an average of 97% ± 8.92%. Results from the study revealed that the average free glutamic acid content ranged from 0.34 ± 0.20 to 4.63 ± 0.41 mg g^?1 in processed foods, while in prepared dishes it was as low as 0.24 ± 0.15 mg g^?1 in roti canai (puffed bread served with curry or dhal) to 8.16 ± 1.99 mg g^?1 in dim sum (a small casing of dough, usually filled with minced meat, seafood, and vegetables, either steamed or fried). Relatively, the content of free glutamic acid was found to be higher in condiments at 0.28 ± 0 mg g^?1 in mayonnaise to 170.90 ± 6.40 mg g^?1 in chicken stock powder.     

Zataria multiflora Boiss essential oil and sodium acetate: how they affect shelf life of vacuum‐packaged trout burgers

The preservative effects of Zataria multiflora Boiss essential oil (ZEO) at 0.025%, 0.05% and 0.1%, sodium acetate (SA) at 2% and their combination on the quality changes of vacuum‐packaged trout burgers during 21‐day refrigerated storage (4 ± 1°C) were investigated. Results showed that control and ZEO‐treated samples reached undesirable levels of rancidity (P < 0.05) at 15th day, whereas samples with the combined effect of SA and ZEOs, especially at higher concentrations, proved to be more stable in sensory, biochemical (PV, TBA, FFA and pH) and microbiological analyses (P < 0.05). Therefore, ZEO+SA‐treated samples showed good overall acceptability even until 21st day. Regarding the results obtained from ZEO‐treated samples, it becomes apparent that combined application of SA and ZEO extended the shelf life of fish burgers during cold storage to 21 days, 1.4‐fold longer than other treatments, which indicates the potential application of synergistic activity of these agents in vacuum‐packaged fishburgers.     

Characteristics of Aspergillus niger xylanases produced on rice husk and wheat bran in submerged culture and solid‐state fermentation for an applicability proposal

Xylanolytic rich filtrates were obtained by A. niger sp in both submerged and solid‐state culture using rice husk or wheat bran as the only carbon source. Filtrates obtained on rice husk showed the highest activities (~6500 and 5200 U g^?1, respectively). Independent of carbon source, these filtrates were very stable in an acidic pH range (4–7) and mild temperatures, with high half‐life time values (more than 7 h at 50 °C) in the corresponding inactivation kinetic models. Also the effect of different metallic ions and denaturing substances was verified finding that these enzymes are not metaloproteins, and metals as Hg²⁺ and Pb²⁺ caused the greatest loss of xylanolytic activity (not higher than 30%). Xylanases produced by this A. niger strain showed important features that make them potential candidates for applications on human and livestock food industries.     

Bifurcaria bifurcata: a key macro‐alga as a source of bioactive compounds and functional ingredients

The aim of this work was to study the proximate composition and the bioactive profile of Bifurcaria bifurcata. It contains 73.31 ± 0.69% of moisture, 8.57 ± 0.11 g per 100 g dry weight (d.w.) of protein, 5.81 ± 0.14 g per 100 g d.w. of lipid content and 30.15 ± 0.00 g per 100 g d.w. of ash. The polyunsaturated fatty acids were the most abundant fatty acid (FA), accounting for 2426.56 mg per 100 g which represents 41.77% of the total FA. The methanolic fraction showed high quantity of polyphenols (220.01 ± 0.010 phloroglucinol equivalents g^?1 extract), DPPH radical reduction capacity (EC₅₀:58.82 μg mL^?1) and oxygen radical absorbent capacity (3151.35 ± 119.33 μmol Trolox equivalents g^?1 extract). The highest antimicrobial effect was observed against Pseudomonas aeruginosa (11.3 ± 1.5 mm) and Saccharomyces cerevisiae (IC₅₀:17.07 μg mL^?1) induced by methanolic and dichloromethane fractions, respectively. Dichloromethane fraction revealed the highest antitumor activity on Caco‐2 and HepG‐2 cells. Bifurcaria bifurcata can be a promising source of bioactive compounds and functional ingredients.     

Lycopene: A natural antioxidant for anhydrous buffalo milk fat

The potential of lycopene extract, to enhance the shelf life of anhydrous buffalo milk fat, at five levels, viz. 30, 60, 90, 120 and 150 ppm, was evaluated. Lycopene was found significantly (P < 0.05) effective in preventing the development of oxidative rancidity. The overall preference score for samples containing 30, 60, 90, 120 and 150 ppm of lycopene were 7.43, 7.60, 7.80, 7.96 and 7.90, respectively, and found to be significantly higher than the control (no lycopene, 6.79). The overall preference score with 200 ppm BHA was 7.94, which was not significantly different from ghee samples containing 120 and 150 ppm lycopene.     

Partial purification of a polygalacturonase from a new Aspergillus sojae mutant and its application in grape mash maceration

The use of polygalacturonase (PG) preparations in winemaking promotes the release of phenolic compounds. A PG from a new source, Aspergillus sojae mutant, was semi‐purified and tested for grape mash maceration. Crude extract (CE), a commercial pectinase, and two high PG activity semi‐purified preparations, F_I and F_II, were applied for maceration at PG activity of 3.5 U g^?1 of grape for 46 h. Enzyme‐assisted maceration significantly (P < 0.05) increased the total phenolic content from 255.8 to 916.3 ± 5.2, 5732.9 ± 9.9, 563.4 ± 6.7 and 620.6 ± 18.4 mg L^?1 for CE, commercial pectinase, F_I and F_II, respectively. The content of individual phenolics such as gallic, protocatechuic, chlorogenic and p‐coumaric acids was improved. Principal component and hierarchical clustering analyses suggested that CE has a better performance upon the release of phenols. Semi‐purified preparations acted similar to commercial pectinase. These findings open an opportunity for the potential use of PG from the mutant strain as an alternative macerating enzyme.     

Comparative assessment of two extraction procedures for determination of bioactive compounds in some berries used for daily food consumption

Two extractions with methanol and water were used to determine the antioxidant and binding properties of some berries as a supplement to food. Fluorometry, FTIR spectra and radical scavenging assays were used for characterisation of bioactive compounds (polyphenols, flavonoids, flavanols and tannins) and the levels of their antioxidant activities (AAs). The contents of bioactive compounds and AAs in water and methanol polyphenol extracts in gooseberries, blueberries and cranberries differed, but not always significantly. Water extracts of gooseberries showed the lowest amounts of polyphenols (mg GAE g^?1), 6.24 ± 0.6, and flavonoids (mg CE g^?1), 0.29 ± 0.01, and AAs (μMTE g^?1) determined by DPPH, FRAP, ABTS and CUPRAC assays such as 6.05 ± 0.6, 8.07 ± 0.9, 18.70 ± 1.8 and 13.44 ± 1.2, respectively, in comparison with blueberries and cranberries. Polyphenol content highly correlated with antioxidant activity (R² from 0.94 to 0.81). The quenching properties of berries were studied by the interaction of water and methanol polyphenol extracts with HSA by 3D fluorescence. In conclusion, the bioactivity of gooseberries was lower than in blueberries and cranberries. Gooseberries can be used as a new source for food consumption and supplementation based on their antioxidant and binding properties. 3D fluorescence spectroscopy and FTIR spectroscopy can be applied as additional analytical tools for rapid estimation of the quality of different food products.     

Assessment of thermo‐oxidative rancidity in sunflower oil and fried potato chips stabilised with oleoresin sage (Salvia officinalis L.) and ascorbyl palmitate by altered triglycerides and electronic nose

Oleoresin sage (Salvia officinalis) (SAG) (200–1500 mg kg^?1), ascorbyl palmitate (AP) (100–300 mg kg^?1) and TBHQ (200 mg kg^?1) were assessed for delaying the thermo‐oxidation in sunflower oil (SO) during 18 h of frying (180 °C). Electronic nose compared the global aroma fingerprints of potato chips fried in oils. The chemical rancidity indices viz., fatty acids, total polar compounds (TPC), altered triglycerides (dimers, polymers, oxidised monomers, diglycerides), free fatty acids, conjugated dienes and induction periods were monitored along with physical indices viz., viscosity and colour. SO_SAG+AP (1309.62 + 270.71 mg kg^?1) outperformed SO_TBHQ by preserving polyunsaturated fatty acids (60.48% vs. 56.23%), retarding TPCs (28.16% vs. 29.91%), triglyceride dimers (90.24 vs. 95.82 mg g^?1) and polymers (25.40 vs. 26.98 mg g^?1) concomitantly extending the oil disposal time (basis 25% TPC) (15.9 vs. 14.7 h). The postfrying viscosity, colour values and global aroma fingerprints of fried chips indicate a close match between SO_SAG+AP and SO_TBHQ.     

Freshness and quality attributes of cold stored Atlantic bonito (Sarda sarda) gravad

Quality and safety parameters of Atlantic bonito gravad during 42 days of storage at 7 ± 1 °C were analysed using monitoring sensory quality, microbial contamination, nucleotide degradation products, biogenic amines (BA), trimethylamine (TMA) and thiobarbituric acid reactive substances (TBARS). The shelf‐life of vacuum packed Atlantic bonito gravad was found to be 28 days. Total viable count (TVC) did not exceed 6 log CFU g^?1. Malonodialdehyde (MDA) content did not surpass 10 mg kg^?1. Nine biogenic amines were detected. Histamine level at the end of the storage was 355.3 mg kg^?1. TMA increased from 53.9 to 619.1 mg kg^?1. Among indicators based on the products of nucleotide degradation, the H value is best correlated with the sensory assessment. It can be concluded that the storage temperature of bonito gravad must be below 7 °C to prevent the threat to safety and quality posed by biogenic amines, especially histamine.     

Microbial inactivation and quality improvement of tomatoes treated by package film with allyl isothiocyanate vapour

In‐package sanitisation was developed using polylactic acid (PLA) films with allyl isothiocyanate (AIT) vapour. Tomatoes were artificially inoculated with Escherichia coli, Geotrichum candidum and Fusarium oxysporum and stored in clamshell boxes with the film fixed to the underside of the lid. The changes in bacterial and fungal populations and the quality of tomatoes during storage at 4 and 10 °C were evaluated. The results revealed that the film treatment (4 × 8 cm² film in 1 L box) reduced the populations of inoculated bacteria and fungi on tomatoes by 2–3 log CFU g^?1, and then significantly (P < 0.05) inhibited their growth during the 21‐day storage period at both temperatures. Tomatoes subject to film treatment had fewer changes in quality (colour, firmness, contents of total soluble solid, titratable acids and vitamin C) than the control samples during storage. The antimicrobial PLA film can be used for in‐package sanitisation to extend the shelf‐life of packaged tomatoes or similar perishable vegetables.     

Application of ultrafiltration in the study of phenolic isolates and melanoidins from pale and black brewers' spent grain

Two types of brewers' spent grain (BSG), pale and black, were studied employing ultrafiltration (UF cut‐off, 10 kDa) to obtain high‐molecular‐weight (HMW) and low‐molecular‐weight (LMW) phenolic fractions from one pale (P2) and one black (B2) BSG extracts. Of the four UF fractions obtained, the HMW B2 fraction had highest level of polyphenols (5.73 ± 0.25 mg GAE g^?1 BSG dw) and protein (18.82 ± 0.41 mg protein g^?1 BSG dw). Metal‐chelating ability and antioxidative properties were also identified. Antioxidant activity evaluated using the DPPH and FRAP assays, indicated that activity in B2 extracts was associated mainly with the HMW fraction (3.10 ± 0.10 and 2.49 ± 0.09 TE g^?1 BSG dw, respectively), whereas in P2 samples, antioxidant activity was highest in LMW fractions (0.58 ± 0.01 and 0.92 ± 0.03 TE g^?1 BSG dw, respectively). The high antioxidant activity and metal‐chelating ability observed for black BSG extracts may be attributed to the presence of coloured melanoidinic structures.