Effect of partial replacement of potassium lactate and sodium diacetate by natural green tea and grape seed extracts and postpackaging thermal treatment on the growth of Listeria monocytogenes in hotdog model system

Low‐ (5%) and high‐fat (20%) chicken and turkey hotdogs were formulated in three groups: no antimicrobials (control), chemical preservatives (potassium lactate and sodium diacetate) alone and partial replacement of chemical preservatives by green tea (GTE) and grape seed extracts (GSE), surface inoculated (c. 10³ CFU g^?1) with Listeria monocytogenes, treated with or without heat treatment (65 °C for 104 s) to determine the growth of L. monocytogenes until spoilage (28 days). Maximum growth inhibitions (c. 2.0 CFU g^?1) were observed in the treatments having chemical preservatives and plant extracts regardless of the meat and fat type. Furthermore, plant extracts along with chemical preservatives demonstrated additional inhibitory effect on the growth of L. monocytogenes survivors in chicken hotdog samples followed by postpackaging heat treatment. Results demonstrated that natural GTE and GSE can partially replace the chemical preservatives and further enhance the antilisterial activities when combined with heat treatment.     

Immunomodulatory and antioxidative potential of herb (Pueraria tuberosa) in mice using milk as the carrier

Eighteen healthy male mice were divided into three equal groups and given specific diets for a period of 28 days: Group M were fed a normal synthetic diet (NSD) and milk; Group P were fed NSD and Pueraria tuberosa (PT) extract (0.4%), while the diet of group PM was NSD supplemented with PT extract (0.4%) and milk. The phagocytic activity and immunoglobulin A (in intestines) and immunoglobulin G (serum) levels increased significantly in comparison with group M in PT supplemented groups after a period of 28 days. Group P and Group PM showed significantly higher reduced glutathione level and significantly lowered thiobarbituric acid reactive substances levels in liver and red blood cells as compared to control.     

Recovery of anthocyanins from grape pomace extracts (Vitis vinifera L. cv. Cabernet Mitos) using a polymeric adsorber resin

Anthocyanins from a Cabernet Mitos grape pomace were extracted without sulfitation, purified and concentrated on a laboratory scale by adsorption to a styrene–divinylbenzene copolymerisate. The pigment loss during sample loading and washing of the column with water was negligible. Elution was performed with acidified methanol, ethanol and 2-propanol, respectively. The recovery rates ranged from 96 to 100% of anthocyanins when methanol was used, from 86 to 96% for ethanol and from 78 to 88% when pigments were eluted with 2-propanol. The temperature during adsorption and desorption (25 and 50 °C) did not significantly influence the pigment binding capacity. The recovery rates were not affected by the scale-up from laboratory to pilot-plant adsorption experiments. The use of polymeric resins facilitates nonthermal anthocyanin concentration since highly pigmented alcoholic eluates were obtained which can further be concentrated under mild conditions. The present study provides systematic data on adsorber technology increasingly used for the recovery of plant secondary metabolites.     

Effect of starter cultures on the quality of Suan yu,a Chinese traditional fermented freshwater fish

The generation of volatile compounds of four starter cultures composed of isolated microorganisms from traditional Suan yu was investigated. The cultures included two pure starters (PS1: Lactobacillus plantarum 120 and PS2: Pediococcus pentosaceus 220) and two mixed starters (MS1: L. plantarum 120, Staphylococcus xylosus 135 and Saccharomyces cerevisiae 31 at 1:1:1; MS2: P. pentosaceus 220, S. xylosus 135 and S. cerevisiae 31 at 1:1:1). Naturally fermented Suan yu was used as control. The volatile compounds were collected from the headspace of the samples by Solid‐phase microextraction and analysed by gas chromatography–mass spectrometry. The type and total content of volatile compounds in the mixed‐starter‐fermented fish were higher than those of the pure‐starter‐fermented samples and control. A total of seventy nine and eighty volatile compounds were detected in Suan yu fermented with MS1 and MS2, respectively, with ethanol as the predominant compound and hexanal, ethyl acetate, 3‐methylbutanol, 3‐hydroxy‐2‐butanone, hexanoic acid ethyl ester and 2,3‐butanedione as the other compounds. Furthermore, the sensorial acceptance of the different products with mixed starter cultures seemed to improve the quality of Suan yu products.     

Changes in volatile aroma compounds of pineapple (Ananas comosus) during freezing and thawing

Changes in the volatile aroma compounds of pineapple (Ananas comosus) during freezing and thawing were compared against fresh samples to determine the effect of freezing on pineapple flavour. An HS‐SPME–GC–MS analysis showed that the Smooth Cayenne pineapple variety had nineteen volatile compounds, in four classes of compounds including fourteen esters, two hydrocarbons, two sulphur‐containing compounds and one lactone. The main characteristic volatile compounds of the fresh pineapple were methyl hexanoate, ethyl hexanoate, ethyl 3‐methylthiopropanoate and 1‐(E,Z)‐3,5‐undecatriene. Freeze–thaw cycles were associated with the loss of some volatile aroma compounds, particularly the esters which were found to be the main characteristic of fresh pineapples. The freezing and thawing process was found to cause damage to the pineapple tissues due to ice recrystallisation and dehydration which lead to the reduction of volatile aroma compounds.     

Volatile secondary metabolites of Greco (Vitis vinifera L.) must

Greco grape (Vitis vinifera L.), a typical white variety of Campania region in the South of Italy, was investigated for the first time determining volatile‐free and glycosidically bound secondary metabolites that could be at the base of the aroma profile of DOCG ‘Greco di Tufo’ wines. C₁₈ reversed‐phase isolates of ‘Greco’ musts have been investigated by gas chromatography/mass spectrometry. ‘Greco’ must resulted characterised by a content of glycoconjugated terpenoids ranging from 180 to 370 μg L^?1. Linalool and geraniol detected in the ‘Greco’ must above their odour thresholds could explain a floral character attributed to the wine. Guaiacol in free fraction, 4‐vinylguaiacol and eugenol in the bound fraction could be at the origin of nutty and spicy notes of the wine. Some observations of this study also show that precursors of floral, spicy and nutty odorants seem to be enhanced by clay soil and good sun exposure.     

Identification of the aroma compounds in stinky mandarin fish (Siniperca chuatsi) and comparison of volatiles during fermentation and storage

Identification of aroma compounds in Stinky Mandarin fish (Siniperca chuatsi) and comparison of volatiles during fermentation (with spices and salt) and storage were analysed by electronic nose (e‐nose) combining with gas chromatography–mass spectrometry (GC‐MS). Among the sixty‐one detected volatiles, thirteen aroma‐active compounds, especially linalool, were identified in stinky mandarin fish according to thresholds and concentrations. Totally, twenty‐four aroma compounds correlated well with the periods of fermentation and storage. Trimethylamine, indole, sulphur‐containing compounds, acetic acid, esters and phenols increased continually, while aldehydes decreased. According to these quality indicators, e‐nose data using principal component analysis showed a clear discrimination of the fermented fish and were in good agreement with the results of GC‐MS. In conclusion, fermentation favoured to retard spoilage and provided new aroma compounds. The technique employing an e‐nose in combination with GC‐MS could compare and identify the aroma and quality of stinky mandarin fish.     

Analysis of odour‐active compounds of black mangrove (Avicennia germinans L.) honey by solid‐phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The volatile compounds of Cuban black mangrove (Avicennia germinans L.) honey were analysed by solid‐phase microextraction (SPME) followed by gas chromatography–mass spectrometry and gas chromatography–olfactometry. A total of 66 compounds were positively identified in this product for the first time. Application of the aroma extract dilution analysis in a novel approach, which consisted of carrying out successively dilutions of the honey sample with a synthetic honey before the SPME, revealed 17 odour‐active areas in the flavour dilution factor range of 32–1024. On the basis of the quantitative data and odour thresholds, odour activity values (OAV; ratio of concentration to odour threshold) were calculated. Sixteen compounds showed OAVs >1, among which dimethyl sulphide, 3‐methyl butanal, 2‐methylbutanal, heptanal, octanal, phenylacetaldehyde, (Z)‐linalool oxide, (E)‐linalool oxide, nonanal, hotrienol, isophorone, lilac aldehyde A, 1‐nonanol, decanal, 4‐vinyl‐2‐methoxyphenol and (E)‐β‐damascenone showed the highest values and should be considered as the most odour‐active compounds, particularly (E)‐β‐damascenone, nonanal and decanal.     

Metabolic profiling of Angelica acutiloba roots utilizing gas chromatography-time-of-flight-mass spectrometry for quality assessment based on cultivation area and cultivar via multivariate pattern recognition

Gas chromatography time-of-flight mass spectrometry was applied to elucidate the profiling of primary metabolites and to evaluate the differences between quality differences in Angelica acutiloba (or Yamato-toki) roots through the utilization of multivariate pattern recognition-principal component analysis (PCA). Twenty-two metabolites consisting of sugars, amino and organic acids were identified. PCA analysis successfully discriminated the good, the moderate and the bad quality Yamato-toki roots in accordance to their cultivation areas. The results signified two reducing sugars, fructose and glucose being the most accumulated in the bad quality, whereas higher quantity of phosphoric acid, proline, malic acid and citric acid were found in the good and the moderate quality toki roots. PCA was also effective in discriminating samples derive from different cultivars. Yamato-toki roots with the moderate quality were compared by means of PCA, and the results illustrated good discrimination which was influenced most by malic acid. Overall, this study demonstrated that metabolomics technique is accurate and efficient in determining the quality differences in Yamato-toki roots, and has a potential to be a superior and suitable method to assess the quality of this medicinal plant.     

Developing a potential prebiotic of yogurt: growth of Bifidobacterium and yogurt cultures with addition of glycomacropeptide hydrolysate

This study is aimed at investigating the feasibility of casein glycomacropeptide (GMP) hydrolysates as potential prebiotics in yogurt. The growth performance of Bifidobacterium animalis subsp. lactis (Bb12) was determined in the presence of GMP hydrolysates produced by the action of proteolytic enzymes (trypsin and papain) with various degrees of hydrolysis. The growth‐promoting effect of GHP on Lactobacillus bulgaricus and Streptococcu thermophilus were also evaluated. Results showed that the optimum hydrolysis time of GMP with trypsin or papain for Bb12 growth promotion was 2 and 0.5 h, respectively. Compared with GMP and its trypsin hydrolysate, the GMP hydrolysate produced with papain (GHP) was the best for Bb12 growth, which obtained the highest viable count (9.3 log cfu mL^?1) and the lowest pH of 4.69. The obtained GHP significantly improved the growth of S. thermophilus (P < 0.05), while it had little effect on the growth of L. bulgaricus (P > 0.05)., The viable count of Bb12 of the yogurt obtained with the addition of 1.5% GHP was about four times higher than that of the control without GHP addition. The growth‐promoting effect of GHP might be related to its high content of Glu, Leu and Ala while had no direct relationship with sialic acid content.     

γ‐Glu‐Met synthesised using a bacterial glutaminase as a potential inhibitor of dipeptidyl peptidase IV

This study describes γ‐glutamyl dipeptides as competitive inhibitors of dipeptidyl peptidase‐IV (DPP‐IV), and the feasible synthesis of γ‐Glu‐Met through transpeptidation catalysed by a commercial glutaminase of Bacillus amyloliquefaciens. γ‐Glu‐Met, γ‐Glu‐Leu, γ‐Glu‐Phe, γ‐Glu‐Trp or γ‐Glu‐Tyr exhibited a competitive inhibitory effect on DPP‐IV. The yield of γ‐Glu‐Met was 26.16% under optimised conditions: 200 mm Gln, 20 mm Met, 0.1 U mL^?1 enzyme, pH 9.0, 37 °C and reaction time 3 h. For the first time, the side products containing characteristic sequences, that is poly‐γ‐glutamyl short chains with a terminal Met residue (γ‐Glu‐γ‐Glu‐Met and γ‐Glu‐γ‐Glu‐γ‐Glu‐Met) were identified. The superiority of the commercial glutaminase in the synthesis of DPP‐IV‐inhibitory peptides can enable the application of this novel process for manufacturing γ‐glutamyl‐peptides as potential functional ingredients in the type 2 diabetic diet.     

Determination of rosmarinic acid and luteolin in Perilla frutescens Britton (Labiatae)

An analytical method for measuring rosmarinic acid (RA) and luteolin (Lut), the major polyphenolic substances in Perilla frutescens Britton (Labiatae) was established. High‐performance liquid chromatography was used to determine the concentration of RA in perilla leaf solutions prepared by two successive extractions with water–acetone–hydrochloric acid (20:80:1, v/v/v). The concentration of Lut in solutions prepared by two successive extractions with ethanol–hydrochloric acid (100:1, v/v) was determined by liquid chromatography–mass spectrometry. The mean concentrations of RA and Lut in the same samples of perilla leaves were 3.95 ± 0.42 and 0.039 ± 0.004 mg·g^?1, respectively, with the concentration of RA being 100 times greater than that of Lut. It was also demonstrated that there were seasonal changes in the RA concentration of perilla leaves collected from the same field and that RA levels varied between different growing areas. Copyright © 2006 Society of Chemical Industry     

A systematic approach for extraction of phenolic compounds using parsley (Petroselinum crispum) flakes as a model substrate

The impact of extraction methodology and polarity of extraction solvents on the assay of phenolic compounds was investigated using parsley (Petroselinum crispum) flakes as a model substrate. This systematic study was undertaken to address substantial variations in the extraction procedures, solvents and conditions as described in the recent literature. Five different extraction procedures [shaking, vortex mixing, sonication, stirring and pressurized liquid extraction (PLE)] and three different solvents (methanol, ethanol and acetone), with five different solvent to water ratios per solvent, were used for extraction. Extracts were analyzed for phenolic content by high‐performance liquid chromatography and Folin–Ciocalteu assays. The yields of phenolic compounds extracted with a pressurized liquid extractor were comparable to or better than those of four classical extraction procedures. Optimum extraction efficiency with PLE was obtained when extractions were performed with four extraction cycles using ethanol–water (50:50, v/v). The amount of apiin (4,5,7‐trihydroxyflavone 7‐apiosylglucoside) and malonylapiin (apigenin malonylapiosylglucoside) isolated from parsley varied with the composition of extraction solvent. Apiin extractability was found to be a maximum when the solvent (ethanol, methanol or acetone) to water ratio was 30:70 (v/v), whereas higher amounts of malonylapiin were isolated with a reverse solvent to water ratio (70:30, v/v). Malonylapiin was not detected when parsley samples were extracted with organic solvent to water ratios of 10:90 (v/v) and 30:70 (v/v). Published in 2006 by John Wiley & Sons, Ltd     

A comparison of the peel oil components of Australian native lime (Microcitrus australe) and Mexican lime (Citrus aurantifolia Swingle)

The essential oil components extracted from the pericarp layer of two varieties of lime fruit, viz. Mexican lime (Citrus aurantifolia Swingle) and an Australian native lime (Microcitrus australe) have been analysed by gas chromatography/mass spectrometry. Thirty‐three components were identified in M australe and 34 in C aurantifolia. The compound types comprised monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpenes and coumarins. For the more volatile monoterpenoid compounds, the major component was limonene, with significant amounts of γ‐terpinene, β‐pinene, geranial, neral, neryl acetate and geranyl acetate. From an examination of the nature and contents of individual components, there was no indication that any one compound might be responsible for the predominant aroma impact. The possible contribution to aroma differences due to quantitative differences in the amounts of these components is discussed. However, sensory evaluation indicated that there was little or no difference between the aromas of the two oils. Copyright © 2004 Society of Chemical Industry     

Effect of simulated gastrointestinal digestion on phenolic composition and antioxidant capacity of cooked cowpea (Vigna unguiculata) varieties

Consumption of diets rich in phenolic compounds has been associated with reduced risk of chronic diseases. The effect of cooking and simulated gastrointestinal digestion on phenolic compounds and antioxidant properties of two cowpea (Vigna unguiculata) types was determined. Phenolic acids, flavan‐3‐ols and flavonols were the main groups of phenolic compounds identified. Cooking and simulated enzyme digestion of the cooked cowpea samples rendered some phenolics less extractable (possibly by promoting binding with other food components) or more extractable (possibly by release of bound forms). Total phenolic contents and radical scavenging properties of the cowpeas were reduced upon cooking, but increased upon simulated enzyme digestion. Cowpea extracts inhibited human LDL oxidation at a concentration of 2 mg mL^?1 possibly due to their phenolic content. Phenolic compounds in cowpea can potentially protect against cardiovascular diseases for which LDL oxidation is a risk factor.