Changes in protein fractions of rainbow trout (Oncorhynchus mykiss) gravads during production and storage

Gravad fish products belong to a group of low-processed products obtained from fresh fish by sprinkling fillets with a mixture of sugar and salt and then placing them in cold storage. Little is known about changes in the tissue during the production and storage of gravads. The purpose of the present study was to investigate the type and scope of changes in rainbow trout (Oncorhynchus mykiss) gravad proteins during processing and vacuum storage at 3 °C and −30 °C. The results showed that the solubility of protein was barely affected by the gravading process, but did change during the cold storage and freezing of the gravad. Catheptic activity decreased with gravading and further storage. A SDS-PAGE analysis revealed that the intensity of the M-protein and troponin bands was reduced, while the bands of α-tropomyosin and the myosin heavy chain increased when the trout muscle was subjected to the gravading process. Two bands with molecular weights of 255 and 135 kDa disappeared in the gravad, and new bands with molecular weights of 163 and 117 kDa appeared. An HPLC analysis revealed that gravading had a limited effect on the relative areas of peaks corresponding to low molecular weight substances of protein origin, while more significant changes were observed during gravad storage. Moreover, the gravading process caused a lowering of the actin and myosin denaturation temperature, which was proved using the DSC method. In conclusion, changes in rainbow trout muscle protein appeared to have a crucial effect on product quality.     

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%.     

Biochemical changes in developing wheat grains. Changes in nitrogen fractions,amino acids and nutritional quality

Two spring wheat cultivars (Triticum aestivum L. em Thell.), one tall (Chris) and the other semi-dwarf (Era), with different yields and grain protein potentials, were grown in controlled environment chambers to compare the nitrogen fractions, amino acids and nutritional quality in developing grains at 12, 22, 29 and 36 days after heading. The proportions of gliadin I, gliadin II and glutenin II increased and those of albumin and globulin decreased as the wheat cultivars matured. The amount of lysine, methionine, threonine, valine, tyrosine, alanine, aspartic acid and glycine was lower and that of glutamic acid and proline was higher with grain development in both cultivars. At 12 days after heading Era had a higher content of amino acids (16 g^?1 N) than Chris. Isoleucine was the first limiting amino acid in Era and Chris at the first collection period whereas at later stages lysine was the limiting amino acid in both cultivars. Chemical score, essential amino acid index, requirement index and calculated biological value all decreased as the grain matured and, except for the 12-days collection period, the data were almost similar for both the cultivars.     

Chemical and microbiological quality of grass carp (Ctenopharyngodon idella) slaughtered by different methods

The effect of two slaughter methods (immersion in ice-water slurry and electrical stunning followed by ice slurry asphyxiation) on chemical and microbiological parameters of grass carp (Ctenopharyngodon idella) stored in ice for 20 days was evaluated. No differences in total volatile basic nitrogen (TVB-N), pH, carbohydrate or protein content of mucus were observed between the slaughter methods. Ice-slaughtered fish had lower bacteria counts at the beginning of storage, but higher counts than fish slaughtered by electricity at the end of storage (p < 0.05). However, no significant differences in the shelf life were observed between the slaughter methods evaluated (limit of acceptability – counts > 3 × 10⁶ CFU g⁻¹ – attained after 13–16 days). Results indicated that the chemical parameters evaluated have a limited applicability to assess the shelf life of grass carp stored in ice, since pH limit (6.8) was exceeded after 4 days, while TVB-N limit (30 mg%) was not attained after 20 days of storage.     

Short communication: Viability of culture organisms in honey-enriched acidophilus-bifidus-thermophilus (ABT)-type fermented camel milk

The aim of this research was to monitor the survival during refrigerated storage of Lactobacillus acidophilus LA-5 (A), Bifidobacterium animalis ssp. lactis BB-12 (B), and Streptococcus thermophilus CHCC 742/2130 (T) in cultured dairy foods made from camel and, for comparison, cow milks supplemented with black locust (Robinia pseudoacacia L.) honey and fermented by an acidophilus-bifidus-thermophilus (ABT)-type culture. Two liters of dromedary camel milk and 2 L of cow milk were heated to 90°C and held for 10 min, then cooled to 40°C. One half of both types of milk was fortified with black locust honey at the rate of 5.0% (wt/vol), whereas the other half was devoid of honey and served as a control. The camel and cow milks with and without honey were subsequently inoculated with ABT-5 culture and were fermented at 37°C until a pH value of 4.6 was reached. Thereafter, the probiotic fermented milks were cooled to 15°C in ice water and were each separated into 18 fractions that were transferred in sterile, tightly capped centrifuge tubes. After 24 h of cooling at 8°C (d 0), the samples were stored at refrigeration temperature (4°C). Three tubes of all 4 products (i.e., fermented camel and cow milks with and without honey) were taken at each sampling time (i.e., following 0, 7, 14, 21, 28, and 35 d of storage), and the counts of characteristic microorganisms and those of certain spoilage microbes (yeasts, molds, coliforms, Escherichia coli) were enumerated. The entire experimental program was repeated twice. The results showed that addition of black locust honey at 5% to heat-treated camel and cow milks did not influence the growth and survival of starter streptococci during production and subsequent refrigerated storage of fermented ABT milks. In contrast, honey improved retention of viability of B. animalis ssp. lactis BB-12 in the camel milk-based product during storage at 4°C up to 5 wk. No spoilage organisms were detected in any of the samples tested in this study. In conclusion, supplementation of cultured dairy foods, especially those made from camel milk, with honey is recommended because honey is a healthy natural sweetener with a variety of beneficial microbiological, nutritional, and sensory properties.     

Biochemical intervention of ergothioneine-rich edible mushroom (Flammulina velutipes) extract inhibits melanosis in crab (Chionoecetes japonicus)

We investigated the effects of decreasing phenoloxidase (PO) activity and prophenoloxidase (proPO) gene expression on the inhibition of postharvest melanosis formation in the red queen crab, Chionoecetes japonicus. The cDNA of proPO from hemocytes of C. japonicus was partially cloned and sequenced. Immersion of live crabs in a 1.0% ergothioneine (ESH)-rich mushroom extract (Flammulina velutipes; ME) solution resulted in significant inhibition of haemolymph PO activity and a reduction of the proPO gene expression in hemocytes that consequently controlled melanosis in the crabs during ice storage. Treatments with a 0.05% w/v sodium sulphite solution or a 0.05% w/v 4-hexyl-1,3-benzenediol solution had similar positive effects as the treatment with a 1.0% ME solution in vivo. In vitro experiments showed that authentic l-(+)-ESH inhibited PO activity and decreased proPO gene expression in crab hemocytes. Thus, the application of ESH-rich ME can be a novel alternative to synthetic melanosis-inhibiting agents to control postharvest melanosis in crabs.     

Extraction of pepsin-soluble collagen from grass carp (Ctenopharyngodon idella) skin using an artificial neural network

A multilayer feed-forward neural network trained with an error back-propagation algorithm was used to evaluate the effects of pepsin amount, reaction time and pH on the yield of pepsin-soluble collagen. A positive correlation was observed between the yield and the amount of pepsin and also the reaction time. The yield increased with an increase of pH to nearly 3, thereafter yield decreased. The trained network gave a regression coefficient (r²) of 0.97 and a mean squared error (MSE) of 0.21, which implied a good generalisation of the network. Based on the genetic algorithm, the optimal extraction conditions to obtain the highest yield were determined to be pH 3.4, 53.3 unit/mg of pepsin and 35.2 h. The predicted yield value was 30.3%. As the estimated optimal extraction conditions were used in the actual preparation of the pepsin-soluble collagen, the yield was measured experimentally to be 29.3 ± 0.8%, which was not significantly different (p > 0.05) from the predicted value. The response surface plots showed the yield of pepsin-soluble collagen as a function of two factors under various extraction conditions.     

In vitro antioxidant activity of liquor and semi-purified fractions from fermented squid pen biowaste by Serratia ureilytica TKU013

Antioxidative activities were found in the culture supernatant of Serratia ureilytica TKU013 with squid pen as the sole carbon/nitrogen source. The 4th day supernatant showed the strongest antioxidant activities and the highest total phenolic content. The supernatant was further purified by liquid–liquid partition, and it was found that the ethyl acetate-soluble (EA) extract exhibited the strongest antioxidant activity in a DPPH radical-scavenging assay and this was compared with the positive control, α-tocopherol. This extract was further divided into eight fractions, designated as F1–F8, by silica gel liquid chromatography. In most cases, F4 and F8 were found to possess the strongest antioxidative activities. Significant associations between the antioxidant potency and the total phenolic content, as well as between the antioxidant potency and free amino groups, were found for the supernatant, extract, and fractions. With this method, squid pen waste can be utilized and has potential in the production of functional foods.     

Prebiotic effect of fermented cashew apple (Anacardium occidentale L) juice

Leuconostc mesenteroides B-512F and L. mesenteroides B-742 were cultivated in clarified cashew apple juice to produce prebiotic oligosaccharides. Yeast extract (20 g/L); K₂HPO₄ (g/L) and sucrose (50 g/L) were added to the juice to promote the microbial growth and dextransucrase production. Initial pH was adjusted to 6.5 with H₃PO₄. Fermentations were carried out at 30 °C and 150 rpm for 24 h. The prebiotic effect of the fermented cashew apple juice, containing oligosaccharides, was evaluated through the Lactobacillus johnsonii B-2178 growth. L. johnsonii was incubated for 48 h using fermented cashew apple juice as substrate. Lactobacillus growth was compared to the microbial growth in non-fermented juice and in MRS broth. L. johnsonii growth in the fermented cashew apple juice was threefolds the observed growth in the non-fermented juice.     

Isolation and partial characterization of pepsin-soluble collagen from the skin of grass carp (Ctenopharyngodon idella)

Pepsin-soluble collagen was extracted from the skin of grass carp (Ctenopharyngodon idella) with a yield of 46.6%, on a dry weight basis. Electrophoretic patterns showed that the collagen contained α1 and α2 chains, similar to those of calf skin collagen. The imino acid content of the collagen from grass carp skin was much lower than those of mammalian’s collagens, as also were the transition temperature and denaturation temperature which were only 24.6 °C and 28.4 °C respectively. Peptide maps of the collagen digested by trypsin and V8 protease showed different peptide fragments from those of calf skin collagen and other fish skin collagens, suggesting differences in amino acid sequences and collagen conformation. In addition, the lyophilized collagen sponge from grass carp skin had a uniform and regular network structure, just like calf skin collagen sponge. These results suggest that grass carp skin has potential for use as a supplementary source of collagen.     

Changes in benzo(a)pyrene content in fermented salami

Summary The benzo(a)pyrene (BaP) content of fermented salami was monitored during the technological processes of cold smoking, ripening and storage. The changes in BaP content were not so great as in products smoked with hot smoke. However, the decrease in BaP content caused by destructive action of physico-chemical environmental factors was compensated by succesive dehydration of the fermented product. After recalculating the BaP content on a dry weight basis a concentration decrease was evident. Significant changes were registered during smoking and ripening while storage under different conditions caused no further effect on these changes.

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Gehaltsänderungen an Benzo(a)pyren in fermentierten Salamiwurst

Zusammenfassung Die Arbeit befaßt sich mit Untersuchungen der Änderungen im Benzo(a)pyren-Gehalt in fermentierter Salamiwurst. Diese Änderungen wurden nicht nur während des Räucherungsprozesses mit kaltem Rauch untersucht, sondern auch im Verlauf des Reifeprozesses und der Lagerung des Produktes unter verschiedenen Bedingungen. Aus diesen Ergebnissen kann man feststellen, daß Gehaltsänderungen an Benzo(a)pyren nicht so markant sind wie bei mit warmem Rauch geräucherten Produkten. Andererseits wird die Abnahme an Benzo(a)pyren durch die destruktive Wirkung der physikalisch-chemischen Faktoren der Umwelt durch die successive Dehydratation des fermentierten Produktes kompensiert. Nach Umrechnung des Gehaltes von Benzo(a)pyren auf Trockensubstanz ist aber die Abnahme evident. Markante Änderungen ergaben sich im Laufe der Räucherung und Reifung, während die Lagerung unter verschiedenen Bedingungen ohne Wirkung war.

     

Antioxidant activities of phenolic rich fractions (PRFs) obtained from black mahlab (Monechma ciliatum) and white mahlab (Prunus mahaleb) seedcakes

The antioxidant activities of phenolic rich fractions (PRFs) from crude methanolic extract (CME), and its fractions using ethyl acetate (EAF), hexane (HF) and water (WF) of black mahlab (Monechma ciliatum) and white mahlab (Prunus mahaleb) seedcakes were investigated. The total phenolic compounds were found to be higher in white mahlab than black mahlab seedcakes. The antioxidant activity determined by the DPPH method revealed that black mahlab PRFs had the highest antioxidant activity, compared to white mahlab fractions. The presence of antioxidants in the two mahlab PRFs reduced the oxidation of β-carotene by hydroperoxides from these extracts/fractions. The effect of the two mahlab PRFs on the oxidative stability of corn oil at 70 °C was tested in the dark and compared with butylated hydroxyanisole (BHA). The CME performed better antioxidant activity in inhibiting the formation of both primary and secondary oxidation products. The qualitative and quantitative characterisation of phenolic compounds was carried out by HPLC/DAD.     

Changes in benzo(a)pyrene content in fermented salami.

The benzo(a)pyrene (BaP) content of fermented salami was monitored during the technological processes of cold smoking, ripening and storage. The changes in BaP content were not so great as in products smoked with hot smoke. However, the decrease in BaP content caused by destructive action of physico-chemical environmental factors was compensated by successive dehydration of the fermented product. After recalculating the BaP content on a dry weight basis a concentration decrease was evident. Significant changes were registered during smoking and ripening while storage under different conditions caused no further effect on these changes.     

Thermal and surface behavior of yeast protein fractions from Saccharomyces cerevisiae

An easy and inexpensive method of fractionation of a yeast homogenate was proposed and it is based on differential centrifugation steps of insoluble components and subsequent precipitations of soluble fractions. In this fractionation, the effect of addition of protease inhibitor was studied. The procedure, which was performed in mild conditions in order to minimize protein denaturation, produced four fractions that proceed from distinct parts of the yeast cell and with a different chemical composition: Fr I, Fr II, Fr III and Fr IV. Thermal and surface behavior of these samples was also analyzed. Fr I and Fr II, mainly composed by cell wall debris and membrane cell components, respectively, exhibited an adsorption rate (Δγ/Δt^1/2) ten-fold higher than Fr III and Fr IV, composed by nucleoproteins and cytoplasmic proteins. All fractions exhibited a unique DSC endotherm with different peak temperature (T_p) and enthalpy values (ΔH). Fr IV exhibited the highest T_p value (74 °C) and less affected by inhibitor absence. Fr I and Fr II showed the highest ΔH values (27-47 J/g protein) but they were markedly affected reducing their enthalpy values and increasing their surface properties in absence of protease inhibitor.     

Effects of food additives on biogenic amine formation in Myeolchi-jeot, a salted and fermented anchovy (Engraulis japonicus)

This study was carried out to reduce biogenic amine contents in Myeolchi-jeot, a salted and fermented anchovy (Engraulis japonicus). The effects of various food additives on biogenic amine formation were determined by HPLC. The greatest inhibitory effect on biogenic amine production was observed in the culture treated with glycine. In the culture, the contents of putrescine, cadaverine, histamine, tyramine and spermidine were reduced by 32.6%, 78.4%, 93.2%, 100.0% and 100.0%, respectively, compared to control. The other additives tested had less effect in inhibiting biogenic amine production. Out of food additives tested, glycine was finally applied to the ripening of Myeolchi-jeotin situ, and then overall production of biogenic amines was reduced by up to 63.0% and 73.4%, compared to controls prepared with no and 20% NaCl, respectively. Therefore, it is expected that the findings of this study enhance the safety of not only Myeolchi-jeot but other salted and/or fermented seafood.     

Changes in the antioxidant activity of loach (Misgurnus anguillicaudatus) protein hydrolysates during a simulated gastrointestinal digestion

A two-stage in vitro digestion model system (a pepsin treatment for 2 h followed by a pancreatin treatment for 2 h, both at 37 °C) was used to simulate the process of human gastrointestinal (GI) digestion to determine the changes in antioxidant activities of loach peptide previously prepared by papain digestion. Results showed that the final GI digests contained 38.1% free amino acids, with short chain peptides (<500 Da) making up the rest of the biomass. Enzymatic breakdown of the GI digests increased their hydroxyl (12% increase), 2,2′-azinobis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) (5% increase) radical scavenging activity, the reducing power (77% increase) and the chelating ability of Cu²⁺ (12% increase), compared to the blank. The results showed that the digestion by gastrointestinal proteases can be used to produce antioxidant peptides, with the advantage that the peptides formed will resist physiological digestion in GI tract.     

Diterpene glycosides from Korean fermented red pepper paste (gochujang) and their origin

Two acyclic diterpene glycosides were isolated from the n-butanol layer (50.84 g) of methanol extracts (1639 g) of gochujang (3 kg, wet wt.), Korean fermented red pepper paste. The chemical structures were elucidated as 6E,10E,14Z-(3S)-17-hydroxygeranyllinalool 17-O-α-l-rhamnopyranosyl(1 →$\to$ 4)-[α-l-rhamnopyranosyl-(1 →$\to$ 6)]-β-d-glucopyranoside (1, capsianoside XVIII, 2.3 mg, a novel compound) and capsianoside F (2, 5.3 mg) based on the spectroscopic data of MS and NMR. Compounds 1 and 2 are reported for the first time from gochujang. In addition, the origin of the compounds was determined to be red pepper (Capsicum annuum), which is one of the representative materials of gochujang.     

Functional properties of protein fractions obtained from commercial yellow field pea (Pisum sativum L.) seed protein isolate

Commercial pea protein isolate was separated into water-soluble (WS), salt-soluble (SS), alkaline-soluble (AS) and ethanol-soluble (ES) fractions. AS fraction was the most abundant, constituting about 87% of the proteins in PPI followed by WS, SS and ES fractions in decreasing order. ES fraction consistently formed emulsions with a narrow range of smaller oil droplet sizes (0.6–19 μm) at pH 4.0, 7.0 or 9.0 compared to a wider range of sizes for emulsions stabilised by WS, SS and AS fractions. Emulsions formed with ES fraction were also the most stable (p < 0.05) over the 3 h test period at all the pH values used in this work. The WS fraction had significantly highest (p < 0.05) protein solubility and foaming capacity at all the pH values when compared to solubility of PPI, SS, and ES. Except for AS and ES fractions, foaming capacities of the protein fractions were higher at pH 9.0 than at pH 4.0 or 7.0.     

Phosphine-induced sterility in Ephestia cautella (Lepidoptera: Pyralidae)

The present study was conducted to explore the sterilizing effect of phosphine on Ephestia cautella. Three to four-day old pupae were exposed to 0, 0.007, 0.014, 0.021, 0.028, 0.035, 0.042 and 0.049 mg/l of phosphine for 24 h at room temperature. The normally developed adults of each treatment were pair mated and several physiological and genetical parameters were investigated. The results showed gradual increases with dose in pupal mortality and adult malformation. The crossing results showed no changes in adult longevity and mating frequency. However, consistent reduction was noted in the fecundity and fertility of normally emerged adults. Preliminary data indicated similar levels of inherited sterility in the F₁ adults raised from the above mentioned crosses.     

Nutritional and functional properties of Vicia faba protein isolates and related fractions

The goal of this research was the characterisation of Vicia faba (broadbean) protein isolates and related fractions in order to determine whether this grain legume could be used for production of high quality protein products and other fractions rich in functional components. Alkaline extraction of the defatted seed flour, followed by precipitation at the isoelectric pH, yielded a 92% protein isolate with a high oil absorption capacity. The contents of the favism-inducing glycosides, vicine and convicine, in the isolate were reduced by more than 99% as compared to the original flour, although the amino acid composition was similar to that of the flour. Some of the by-products of protein isolate production may also be of interest from a nutritional and functional point of view. Thus, the oil resulting from hexane extraction of the flour is rich in unsaturated fatty acids, and polyphenols (resulting from extraction of the defatted flour with acetone) showed a high ABTS radical-scavenging activity. In addition, the solid residue (resulting from protein solubilisation) was high in fibre and showed good water absorption. These results show good nutritional and functional properties in V. faba protein isolates and related fractions, which may favour the revalorisation of this traditional bean crop.