Identification and sensory evaluation of flavour enhancers in Japanese traditional dried herring (Clupea pallasii) fillet

Flavour-enhancing components of dried herring fillet (migaki-nishin in Japanese) were isolated and evaluated for their effects on sensory perception. Sensory evaluation revealed that addition of dried herring fillet water-soluble extracts to Japanese noodle soup significantly (P < 0.05) enhanced soup flavour characters, such as thickness, mouthfulness and continuity. The extracts were fractionated by dialysis and chromatography. Fractions containing flavour enhancers were isolated by sensory perception. Results from instrumental analyses showed that the kokumi flavour enhancers in dried herring fillet were creatine and creatinine.     

Changes of lipids in sardine (Sardinella gibbosa) muscle during iced storage

Changes in lipids of sardine (Sardinella gibbosa) muscle during 15 days of iced storage were investigated. Lipid deterioration, lipolysis and lipid oxidation, occurred throughout the storage. The progressive peroxide formation was monitored by the increase in the absorbance band at 3600–3200 cm⁻¹ in Fourier transform infrared (FTIR) spectra and increased peroxide values were observed in sardine muscle up to 6 days of iced storage, followed by a continuous decrease from then for 9 days (P < 0.05). The increase in thiobarbituric acid reactive substances (TBARS) was noticeable throughout the iced storage (P < 0.05). However, no difference in conjugated diene (CD) of sardine muscle was found within the first 12 days of iced storage (P > 0.05). Marked decreases in unsaturated fatty acids, especially eicosapentaenoic acid (EPA; C20:5(n − 3)) and docosahexaenoic acid (DHA; C22:6(n − 3)) were observed as the storage time increased. Those changes indicated that lipid oxidation occurred in sardine muscle. A gradual increase in free fatty acid formation, with decreases in triglyceride and phospholipid contents, was found during iced storage (P < 0.05), suggesting hydrolysis induced by lipases and phospholipases.     

Sensory,microbiological and chemical assessment of the freshness of red mullet (Mullus barbatus) and goldband goatfish (Upeneus moluccensis) during storage in ice

The shelf life of red mullet and goldband goatfish during ice storage were studied in terms of sensory, microbiological and chemical changes. The sensory acceptability limit was 8 days for goldband goatfish (Upeneus moluccensis) and 11 days for red mullet (Mullus barbatus) stored in ice. The TVC level was correlated with sensory assessment. The TVC exceeded 7 log cfu g⁻¹ after 8 days for goldband goatfish, and 11 days for red mullet. At the end of storage period, pH, TVB-N, TBA, FFA and PV for red mullet were 7.84, 47.19 mg/100 g, 0.69 mg MA kg⁻¹, 1.17% oleic acid and 1.58 meq O₂/kg and for goldband goatfish they were 7.53, 43.97 mg/100 g, 0.74 mg MA kg⁻¹, 1.62% oleic acid and 1.68 meq O₂/kg, respectively. In red mullet, agmatine, serotonin, histamine and dopamine became the dominant amines, reaching 7.30, 5.97, 2.52 and 2.31 mg/100 g, respectively. Also the dominant amines for goldband goatfish were 4.37, 3.88, 3.38 and 2.00 mg/100 g for histamine, agmatine, dopamine and putrescine, respectively.     

Composition and non-volatile taste components of Hypsizigus marmoreus

Two strains of Hypsizigus marmoreus (Peck.) Bigelow (Tricholomataceae) are successfully cultivated and commercially available in Taiwan, and their composition and non-volatile taste components of fruit bodies and mycelia were studied. Both fruit bodies were higher than mycelia in contents of carbohydrate, ash and fiber but lower in contents of fat and protein. Total sugar and polyol contents were 45.47-91.50 mg/g and total free amino acid contents were in the descending order of white strain fruit bodies (122.97) > normal strain fruit bodies (95.94) > white strain mycelia (53.20) > normal strain mycelia (46.87 mg/g). Monosodium glutamate-like components of both fruit bodies were 3-4-fold higher than those of both mycelia. Total 5′-nucleotides contents were 6.43-11.02 mg/g with white strain fruit bodies being the highest. Equivalent umami concentrations of both fruit bodies were higher than those of mycelia. Overall, H. marmoreus fruit bodies possessed highly intense umami taste.     

Effect of supplementing ewes’ diet with thyme (Thymus zygis ssp. gracilis) leaves on the lipid oxidation of cooked lamb meat

The aim of this study was to ascertain whether the inclusion of thyme leaves in the diet of pregnant sheep affects the sensorial characteristics and oxidative stability of cooked lamb meat. Thirty-six Segureña sheeps were randomly assigned into three homogeneous groups. One group was fed a basal diet as control, while the diet of the other two groups was modified by substituting 3.75% and 7.5% of the control diet with thyme leaves. TBARS, volatile compounds, and the sensory characteristics of cooked lamb meat were analysed on days 0, 2 and 4. The incorporation of thyme into the animal diet favoured the antioxidant capacity of these cooked lamb meat samples. The cooked meat of lambs from ewes fed thyme leaves showed lower TBARS, hexanal values, rancid odour and rancid flavour scores. No statistically significant differences were detected between the results obtained for the two leaf levels.     

Chemical and DNA authentication of taste variants of Gynostemma pentaphyllum herbal tea

Gynostemma pentaphyllum Makino (Gp) was once used as a sweetener in Japan and is now widely consumed as an herbal tea worldwide for lowering cholesterol levels. Two taste variants, bitter and sweet, of Gp exist in the commercial market, but they cannot be differentiated morphologically nor by existing chemical analytical methods. This has been creating a problem in quality control of Gp products. In the present study, using HPLC-DAD and HPLC–ESI-MS analysis, we found that the Gp saponins, not flavonoids, from the sweet and bitter variants have distinctly different profiles. In addition, the two variants share only 69.01% homology in the ribosomal ITS-1 region, suggesting a phylogenic gap between these two variants. The combinations of chemical profiling and phylogenic analysis clearly confirm, for the first time, the distinction between these two taste variants. This information has direct application in the authentication and quality assessment of the various Gynostemma tea products.     

Umami taste characteristics of water extract of Doenjang, a Korean soybean paste: Low-molecular acidic peptides may be a possible clue to the taste

We investigated the taste characteristics of doenjang water extract (DWE) for component compounds that contribute to its taste. A 1% DWE solution elicited the highest umami taste ratings in a taste profile test. A 3% solution of DWE was used as substitute for 9.4% of monosodium glutamate in a taste soup base, and it masked the bitter taste of hydrolysed animal protein when mixed in solution. DWE was fractionated, based on molecular weights, and fraction IV (F-IV; 1000 > MW ? 500) had the highest peptide contents and elicited the strongest umami taste. The acidic peptide fraction of F-IV elicited the strongest umami taste. The major bound-type amino acids in DWE, F-IV and the acidic peptide fraction were Glu and Asp. These data show that the umami taste characteristics were a result of the low molecular weight acidic peptides naturally produced during the fermentation of soybeans.     

Non-volatile taste components of Agaricus blazei, Agrocybe cylindracea and Boletus edulis

Three species of dried mushrooms are commercially available in Taiwan, namely Agaricus blazei (Brazilian mushroom), Agrocybe cylindracea (black popular mushroom) and Boletus edulis (king bolete), and their non-volatile taste components were studied. All mushrooms were high in contents of carbohydrate, crude fiber and protein but low in contents of crude ash and fat. Arabitol, myo-inositol, mannitol and trehalose were detected in these three mushrooms, whereas glucose was not found in B. edulis. Contents of total soluble sugars and polyols ranged from 150.33 to 225.08 mg/g. Total free amino acid contents were low in these three mushrooms and ranged from 8.97 to 14.91 mg/g. The contents of MSG-like components ranged from 1.24 to 4.40 mg/g were in the descending order of the A. blazei, A. cylindracea and B. edulis. Total 5′-nucleotides contents of A. blazei and A. cylindracea were higher than that of B. edulis whereas flavor 5′-nucleotides content of A. blazei was higher than those of A. cylindracea and B. edulis. Equivalent umami concentrations values in three mushrooms ranged from 10.46 to 135.90 g per 100 g. Overall, these three mushrooms possessed highly umami taste.     

A laboratory assessment of the potential of different strains of the entomopathogenic fungi Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae (Metschnikoff) to control Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) in stored cowpea

Twelve indigenous and exotic isolates of Beauveria bassiana and Metarhizium anisopliae were evaluated for their virulence and their ability to suppress populations of Callosobruchus maculatus in stored cowpea. LT₅₀ values ranged from 3.11 to 6.12 days following immersion in aqueous suspensions containing 1×10⁸ conidia ml⁻¹. Indigenous isolates that had been recovered from C. maculatus were more virulent in laboratory bioassays than exotic isolates from other insects. The two isolates with the shortest LT₅₀ values were compared in dose-response assays by immersion and by exposure to cowpea grains treated with dry conidia. In both assays B. bassiana 0362 was consistently more virulent than M. anisopliae 0351. By immersion, LC₅₀ values on day 6 post-treatment were 9.10×10⁴ and 7.10×10⁵ conidia ml⁻¹ for B. bassiana 0362 and M. anisopliae 0351, respectively. Exposure to treated grains gave LC₅₀ values of 1.15×10⁷ and 4.44×10⁷ conidia g⁻¹ grain for B. bassiana 0362 and M. anisopliae 0351, respectively. In 1 kg batches of cowpea stocked with 50 adult C. maculatus, B. bassiana 0362 at both 1×10⁷ and 1×10⁸ conidia g⁻¹ grain led to significant adult mortality and reduced F₁ emergence relative to untreated populations. At 1×10⁸ conidia g⁻¹ the effect of the fungus persisted into the F₁ generation. The net reproductive rates, R₀, measured 26 days after insects were released were 5.16 and 7.32 for the high and low doses compared to 9.52 for the untreated control.     

Storage stability of liver oil from two ray (Rhinoptera bonasus and Aetobatus narinari) species from the Gulf of Mexico

The effect of storage time on the quality of liver oil from two commercial rajiform species (Rhinoptera bonasus and Aetobatus narinari) captured in the Gulf of Mexico (State of Campeche coast line) was evaluated. Oil characterisation was conducted by physical (specific gravity, saponification index and water content) and chemical analyses (fatty acid content, carotenes and tocopherols) whilst storage stability (peroxide value, free fatty acids, conjugated dienes, anisidine value and changes in docosahexaenoic acid, DHA and content) was studied for 87 days at 25 °C. Increases (p < 0.05) in free fatty acids, conjugated dienes, peroxide value and anisidine value, and a decrease (p < 0.05) in DHA were observed during the storage time for both oil species as oxidation proceeded. It was concluded that R. bonasus and A. narinari oils lasted for 52 and 66 days under these storage conditions, respectively.     

Comparative evaluation of bacterial cellulose (nata) as a cryoprotectant and carrier support during the freeze drying process of probiotic lactic acid bacteria

Nata or bacterial cellulose produced by Acetobacter xylinum was compared for its cryoprotective and carrier support potential for probiotic lactic acid bacteria against other established cryoprotectants like 10% skim milk, calcium alginate encapsulation or 0.85% physiological saline and distilled water. Individual lactic acid bacteria were grown in MRS broth in the presence of nata cubes or the bacterial suspension mixed with either powdered bacterial cellulose (PBC), 10% skim milk, saline or distilled water and freeze dried. These freeze dried cells were stored at temperatures of either 30 °C or 4 °C and periodically checked for viability. The freeze dried cells on carrier supports were directly used to prepare fermented milks to establish the activity of these cultures. Scanning electron microscopy was employed to visualize the support matrix with the attached lactic acid bacteria. The freeze drying process resulted in a 3.0 log cycle reduction in the colony forming units as compared to the original cell suspension in the case of all the lactic acid bacteria. The growth of lactic acid bacteria in the presence of bacterial cellulose (nata) offers a convenient and easy method to preserve bacteria for short durations and use it as a support to carry out other fermentation processes.     

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.     

Nonvolatile taste components of Grifola frondosa, Morchella esculenta and Termitomyces albuminosus mycelia

Three species of mushroom mycelia are commercially available in Taiwan, namely Grifola frondosa (maitake), Morchella esculenta (morel), and Termitomyces albuminosus (termite mushroom), and their nonvolatile taste components were studied. All mycelia were high in contents of carbohydrate, crude fat and protein but low in contents of crude ash and fiber. Arabitol, glucose, mannitol and trehalose were detected in these three mycelia and total amounts of sugars and polyols were 63.69-83.89 mg/g. Total free amino acid contents in three mycelia ranged from 35.67 to 50.37 mg/g. The monosodium glutamate-like components of G. frondosa mycelia (6.51 mg/g) was approximately twofold higher than M. esculenta and T. albuminosus mycelia (3.58 and 3.11 mg/g, respectively). As compared with other components, sweet and bitter components were much higher in these three mycelia. Contents of total 5′-nucleotides in these three mycelia ranged from 13.32 to 26.19 mg/g and were in the descending order of T. albuminosus>M. esculenta>G. frondosa. Equivalent umami concentration of T. albuminosus mycelia was higher than those of G. frondosa and M. esculenta mycelia. Overall, three mycelia possessed highly intense umami taste.     

Lipid characteristics in cooked, chill-reheated fillets of Indo-Pacific king mackerel (Scomberomorous guttatus)

Slices of Scomberomorous guttatus cooked by four different methods (microwave cooking, grilling, steaming and shallow fat frying) were kept chilled at 5 °C for 2 days, reheated by microwave and then evaluated for the changes in the lipid characteristics. The total lipid content for raw sample was 6.0 g/100 g which consist of 49.4 g/100 g saturated (SFA), 6.9 g/100 g monounsaturated (MUFA) and 43.8 g/100 g polyunsaturated fatty acids (PUFA). Upon cooking, the total lipids changed to about 7 (microwave), 11 (grilling), 5 (steaming) and 10 g/100 g (shallow fat frying). These changes are significant, with the exception of steam cooking. Cooking did not significantly affect the percentage of NPL, PL, SFA, MUFA and PUFA in the samples. Frying resulted in the change of the SFA/PUFA ratio more than other cooking methods. A significant (P < 0.05) decrease in the content of EPA was only found in the fried samples. A significant (P < 0.05) decrease in the content of DHA in all cooked samples were also obtained. The n-6/n-3 ratio did not change significantly in all cooked and reheated samples, except for shallow fat fried. Reheating did not significantly affect the NPL and PL contents of the fillets, except for microwave cooked samples. Cooking increases the FFA, PV and TBA of samples; reheating enhances the increase.     

Distribution of the Medea factor M in populations of Tribolium castaneum (Herbst) in the United States

The distribution of the maternally acting, selfish gene Medea⁴ (M⁴) was determined in populations of the red flour beetle, Tribolium castaneum (Herbst), collected in the southern and midwestern United States. We found clear evidence for the existence of two major regional subpopulations, with a boundary that roughly corresponds to 33°N latitude. All 26 strains collected in 10 states north of this latitude were homozygous for the M⁴ allele, while only two of 29 strains collected in six states south of this latitude were homozygous for the allele. Of the remaining 27 southern strains, 21 lacked the M⁴ allele entirely, while six contained a mixture of M⁴ and non-M⁴ alleles. This is the first evidence of either the existence of biotypes or the presence of major barriers to gene flow in wild populations of this ubiquitous insect species.     

Toxicity of ethyl formate to adult Sitophilus oryzae (L.), Tribolium castaneum (herbst) and Rhyzopertha dominica (F.)

Fumigations were conducted using a continuous flow-through laboratory process to maintain constant concentrations of ethyl formate and low levels (<0.8%) of respiratory carbon dioxide. The procedure minimised the effects of sorption by exposing test insects without media and minimised the effect of carbon dioxide by use of continuous flow. The concentration×time (Ct) products of ethyl formate for adult Sitophilus oryzae, Tribolium castaneum and Rhyzopertha dominica at 25 °C and 70% relative humidity for the 6 h exposure were, respectively: (1) LD₅₀ 107.8, 108.8 and 72.8 mg h L⁻¹ and (2) LD_99.5 207.4, 167.1 and 122.2 mg h L⁻¹. Endpoint mortality was reached within 24 h of initial exposure.     

Flavonoids and other phenolic compounds in Andean indigenous grains: Quinoa (Chenopodium quinoa), kañiwa (Chenopodium pallidicaule) and kiwicha (Amaranthus caudatus)

The amount of phenolic acids, flavonoids and betalains in Andean indigenous grains, quinoa (Chenopodium quinoa), kañiwa (Chenopodium pallidicaule) and kiwicha (Amaranthus caudatus), was determined. The total amount of phenolic acids varied from 16.8 to 59.7 mg/100 g and the proportion of soluble phenolic acids varied from 7% to 61%. The phenolic acid content in Andean crops was low compared with common cereals like wheat and rye, but was similar to levels found in oat, barley, corn and rice. The flavonoid content of quinoa and kañiwa was exceptionally high, varying from 36.2 to 144.3 mg/100 g. Kiwicha did not contain quantifiable amounts of these compounds. Only one variety of kiwicha contained low amounts of betalains. These compounds were not detected in kañiwa or quinoa. Our study demonstrates that Andean indigenous crops have excellent potential as sources of health-promoting bioactive compounds such as flavonoids.     

Behavior of Salmonella during fermentation,drying and storage of cocoa beans

Due to cocoa being considered a possible source of Salmonella contamination in chocolate, the behavior of Salmonella during some cocoa pre-processing stages (fermentation, drying and storage) was investigated. The fermentation process was carried out on a pilot scale (2 kg beans/box) for 7 days. Every day a fermentation box was inoculated with a Salmonella pool (ca. 4 log MPN/g). The results showed that Salmonella did not affect (P > 0.05) the growth of the main microorganism groups involved in cocoa fermentation. On the other hand, the pathogen was influenced (P < 0.05) by yeast, acetic acid bacteria and pH. In spite of Salmonella showing counts ≤ 1 log MPN/g in the first days, at the end of fermentation it grew in all samples, reaching counts as high as 7.49 log MPN/g. For drying and storage, cocoa beans were inoculated during the fermentation (experiment A) or during the drying (experiment B). In these stages the decline of the water activity affected the pathogen behavior. In experiment A during the drying, Salmonella count increased in most of the samples. In experiment B either a slight growth or no growth in the samples inoculated up to 48 h was observed, whereas the other samples showed reductions from the initial count. After 30 days of storage at room temperature, the water activity decreased to 0.68, and reductions of Salmonella ranged from 0.93 to 2.52 log MPN/g. Despite the reductions observed during the storage, the pathogen was detected even after 120 days. Therefore, the results showed that Salmonella growth or survival depends on when the contamination occurs.     

Supercritical CO2 extraction of γ-linolenic acid and other lipids from Arthrospira (Spirulina)maxima: Comparison with organic solvent extraction

Freeze-dried biomass of Arthrospira maxima Setchell & Gardner was submitted to supercritical CO₂ extraction using a flow type apparatus at a temperature of 50 °C and a pressure of 250 bar.