Variation in 1‐fructo‐exohydrolase (1‐FEH) and 1‐kestose‐hydrolysing (1‐KH) activities and fructo‐oligosaccharide (FOS) status in onion bulbs. Influence of temperature and storage time

Effects of storage temperature and duration on 1‐fructo‐exohydrolase (1‐FEH) and 1‐kestose‐hydrolysing (1‐KH) activities and trisaccharide (Tri) and fructo‐oligosaccharide (FOS) status in onion bulbs var Tenshin kept for 24 weeks at 10 and 20 °C were investigated. 1‐FEH activity peaked sharply after 10 weeks and seemed to be triggered by a decrease in sucrose content. 1‐KH activity increased during the first 8 weeks and remained stable during the last 8 weeks. Contents of Tri, FOS and total FOS decreased abruptly during the first 8 weeks; however, at 10 °C, contents of Tri, FOS (DP 3–12) and total FOS were lower than those at 20 °C. The consumption rate of fructo‐oligosaccharides also appeared to be higher at 20 °C than at 10 °C, despite the slight degradation in activities observed at this low temperature. 1‐FEH seems to be under the control of a triggering signal which induces its activity, and sucrose seems to be this biochemical signal which initiates dormancy release and the onset of sprouting, as found previously. Thus changes in carbohydrates seem to be a strong indicator of the end of the dormant state of the bulb and the beginning of the sprouting period. Copyright © 2004 Society of Chemical Industry     

In vitro anti‐HSV‐2 activity and mechanism of action of proanthocyanidin A‐1 from Vaccinium vitis‐idaea

The aim of this study was to investigate the in vitro anti‐HSV‐2 activity and mechanism of action of proanthocyanidin A‐1, a compound isolated from Vaccinium vitis‐idaea Linn (Ericaceae). The results demonstrated that proanthocyanidin A‐1 exhibited anti‐HSV‐2 activity. The IC₅₀ value for the XTT assay was 73.3 ± 14.5 µM and the IC₅₀ and IC₉₀ values for the plaque reduction assay were 41.9 ± 2.0 and 62.8 ± 6.3 µM respectively. Proanthocyanidin A‐1 showed no cell cytotoxic effect at concentrations that blocked HSV‐2 infection, with a CC₅₀ value of 282.1 ± 27.5 µM . The mechanism studies demonstrated that proanthocyanidin A‐1 did not reduce viral infectivity but inhibited viral attachment and penetration and affected the late stage(s) of HSV‐2 infection. It was concluded that proanthocyanidin A‐1 suppressed HSV‐2 infection through many modes of action and thus merits further investigation. Copyright © 2004 Society of Chemical Industry     

Glutaminase‐induced deamidation and hydrolysis of casein and metal‐chelating or ACE‐inhibitory activity of the hydrolysates in vitro

Glutaminase (EC 3.5.1.2) was applied in this work to induce deamidation and hydrolysis of casein. Some reaction conditions based on casein deamidation were studied. Three casein hydrolysates with degree of deamidation of 2.8%, 5.8% and 8.5%, or degree of hydrolysis of 2.5%, 3.4% and 4.9%, respectively, were prepared at casein concentration 5% (w/v), glutaminase addition level 400 U kg^?1 casein, reaction temperature 37 °C and reaction times 6, 12 and 24 h, respectively. Evaluation results showed that when iron (II) was added at 60 μm , iron (II)‐chelating powers of three hydrolysates were 41.1, 45.4 and 55.3%, while that of original casein and EDTA were 36.1 and 13.6%. Calcium (II)‐chelating power of three hydrolysates was 1.23, 1.41 and 1.49 mmol g^?1 casein, whereas that of original casein was 1.05 mmol g^?1 casein. Three hydrolysates also had ACE‐inhibitory activity in vitro, with IC₅₀ values from 0.75 to 2.34 mg mL^?1.     

Antioxidant capacity of methanolic and water extracts prepared from food‐processing by‐products

This study aims to evaluate the antioxidant capacity of mango peel, roselle seed, okara (by‐product of soya milk industry), cocoa shell and pink guava (by‐product of pink guava industry) in comparison to 6‐hydroxy‐2,5,7,8‐tetramethylchroman‐2‐carboxylic acid (Trolox). The β‐carotene bleaching, 1,1‐diphenyl‐2‐picrylhydrazyl and reducing power assays were used to determine the antioxidant capacity of selected by‐products by measuring the absorbance at 470, 520 and 700 nm, respectively. The results showed that methanolic extracts of pink guava and cocoa shell exhibited the highest antioxidant activity and free radical scavenging activity compared to other studied samples. Roselle seed water extract exhibited the highest antioxidant activity and free radical scavenging when extracted with water. Pink guava possessed the highest reducing power in methanolic extract at a concentration of 0.16 mg mL^?1. At the same concentration, mango peel exhibited the highest reducing power when extracted with water. The present study shows that pink guava, roselle seed and cocoa shell are potential sources of antioxidant components that can be exploited as food preservative agents or nutraceuticals. Copyright © 2006 Society of Chemical Industry     

The antioxidant activity and transcellular pathway of Asp‐Leu‐Glu‐Glu in a Caco‑2 cell monolayer

Asp‐Leu‐Glu‐Glu (DLEE) is one of the antioxidant peptides purified from Chinese dry‐cured Xuanwei ham in our previous study. In the current work, the stability in a simulated digestion system, the transportation pathway and the antioxidant ability of DLEE were further investigated in a Caco‐2 cell monolayer. In the simulated gastrointestinal digestion system, no oligopeptides were generated. In the transport trial, the inhibitors cytochalasin D increased the transport of DLEE across the Caco‐2 cell monolayer, with P_app values of 3.22 × 10^?6 cm s^?1. A decreased expression occludin was observed with the DLEE incubation in the cell monolayer, and the antioxidant activity showed to be increased gradually in basolateral side. This study indicates that the absorption of DLEE could mainly occur via paracellular transport and provides information about its antioxidant activity after being absorbed across a cell monolayer.     

Characterization,Anti‐Inflammatory and Antiproliferative Activities of Natural and Sulfonated Exo‐Polysaccharides from Streptococcus thermophilus ASCC 1275

Exo‐polysaccharides (EPS) isolated from Streptococcus thermophilus ASCC 1275 were sulfated (31%). High‐performance liquid chromatography identified that EPS was composed of mannose (30.19%), galactose (20.10%), glucose (18.05%), glucosamine (16.04%), galactosamine (9.06%), glucuronic acid (3.55%), and ribose (3.01%). Pro‐/anti‐inflammatory cytokine secretion ratios (IL‐1β/IL‐10, IL‐6/IL‐10, and TNF‐α/IL‐10) of lipopolysaccharide stimulated RAW 264.7 macrophages were significantly decreased by EPS and S.EPS treatments in a dose dependent manner. Furthermore, anti‐inflammatory activities of S.EPS improved 49.3% and 24.0% than those of EPS before or after LPS treatment. The reactive oxygen species were inhibited by EPS and S.EPS by 49.6% and 55.1% at 50 μg/mL, respectively. Inhibition activities of S.EPS on nitric oxide production were 12.9% and 55.4% higher than those of EPS at 10 and 50 μg/mL. Additionally, S.EPS exhibited stronger antiproliferative activity on Caco‐2 and HepG2 cells. Our results indicated that anti‐inflammatory and antiproliferative activities of EPS were significantly (P < 0.01) improved by sulfonation.     

Inhibition of 2‐Amino‐1‐methyl‐6‐phenylimidazo [4,5‐b]pyridine (PhIP) Formation by Alkoxy Radical Scavenging of Flavonoids and Their Quantitative Structure–Activity Relationship in a Model System

The inhibitory effect of 10 flavonoids on the formation of 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) in a creatinine–phenylalanine model system was investigated through electronic spin resonance and a quantitative structure–activity relationship. Alkoxy radicals were observed during the heating process, providing evidence for a radical pathway in the formation of PhIP. The alkoxy radical scavenging capability of the flavonoids was proportional to their inhibition of PhIP formation (IC₅₀). We deduced that flavonoid inhibition of PhIP generation occurs via scavenging of alkoxy radicals during the heating process. Multiple linear regression and partial least squares models were used to elucidate the relationship between PhIP inhibition activity and structure characteristics of the flavonoids. The lipo–hydro partition coefficient and molecular fractional polar surface area of the flavonoids were found to be predictive of the inhibition effect.     

Synthesis and Characterization of Nano‐Encapsulated Black Pepper Oleoresin using Hydroxypropyl Beta‐Cyclodextrin for Antioxidant and Antimicrobial Applications

Previous studies have reported antimicrobial and antioxidant activity of black pepper oleoresin which is associated to its phenolic compounds and piperine. The ability of cyclodextrins to form an inclusion complex with a guest molecule could improve black pepper oleoresin application, bioavailability, and stability in foods. Hydroxypropyl beta‐cyclodextrin (HPBCD) inclusion complex with black pepper olereosin were synthesized using the kneading method and characterized for its physico‐chemical properties and its antioxidant and antimicrobial activities. Inclusion complex size was 103.9 ± 7.6 nm and indicated to be a polydisperse system. The entrapment efficiency was 78.3 ± 3.6%, which suggests that other constituents in black pepper oleoresin have higher affinities for HPBCD than piperine (major compound in black pepper oleoresin). Thermograms showed the disappearance of oxidation peaks of black pepper oleoresin, proving complex formation with HPBCD. Phase solubility results indicated 1:1 stoichiometric inclusion complex formation and an increase of black pepper oleoresin aqueous solubility with HPBCD concentration. Nano‐encapsulation with HPBCD did not affect (P > 0.05) total phenolic content; however, it enhanced (P < 0.05) black pepper oleoresin antioxidant activity. Black pepper oleoresin and its inclusion complex were analyzed for their antimicrobial activity against Escherichia coli K12 and Salmonella enterica serovar Typhimurium LT2. Both free and encapsulated black pepper oleoresin effectively inhibited bacterial growth within the concentration range tested. Black pepper oleoresin encapsulated in HPBCD was able to inhibit Salmonella at lower (P < 0.05) concentrations than its corresponding free extract. Therefore, black pepper oleoresin‐HPBCD nanocapsules could have important applications in the food industry as antimicrobial and antioxidant system.     

Degradation of N‐(1‐Deoxy‐d‐xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐xylulos‐1‐yl)proline using thermal treatment

The formation and degradation of N‐(1‐Deoxy‐d ‐xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d ‐xylulos‐1‐yl)proline, derived from the secondary amine Maillard reaction in xylose‐amino acid model solutions, were detailed in this study. The identification and quantitative analysis of N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline were carried out using high‐performance anion‐exchange chromatography and high‐performance liquid chromatography. The formation of intermediate and advanced products derived from N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline was also tested using an UV‐Vis spectrophotometer to gain a better comparing of the degradation process of the two important Maillard reaction products using thermal treatment. Results showed that the degradation of N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine was more significant than N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline. Moreover, xylose was tested in the degradation products of both N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline, which indicated that the degradation of N‐substituted 1‐amino‐1‐deoxyketoses was a reversible reaction to form reducing sugar.     

Barley Grain Non‐specific Lipid‐Transfer Proteins (ns‐LTPs) in Beer Production and Quality

Plant non‐specific lipid‐transfer proteins (ns‐LTPs) are known for their ability to transfer various lipids between membranes in vitro. These ubiquitous basic proteins, that all share alpha structure stabilized by four disulphide bridges, are characterized by the presence of a hydrophobic cavity able to accommodate lipid molecules. According to molecular mass, this multigene family is subdivided into two subfamilies, ns‐LTP1 (9 kDa) and ns‐LTP2 (7 kDa); both located in the aleurone layer of the cereal grain endosperm. Ns‐LTP1 is a prominent protein in barley grain, malt and beer. Numerous studies performed on its structure and function confirm its important role in grain protection, as well as brewing technology. As the major beer protein crucial for many aspects of brewing, ns‐LTP1 can affect beer production and quality. Comparatively, there is less data available on the less abundant ns‐LTP2. In this review, the focus is on recent progress on the structure, biological and technological function of barley grain ns‐LTP1 and ns‐LTP2, with an emphasis on their importance in brewing.     

High‐pressure high‐temperature extraction of phenolic compounds from grape skins

This study focused on the use of a non‐conventional extraction technology by employing high‐pressure high‐temperature stirred reactor to extract polyphenols from grape skins. Extraction time (15–330 min) and temperature (30–150 °C) were selected as independent variables, and their effects were studied. A preliminary kinetic study on polyphenols extraction revealed that the second‐order model fitted satisfactorily the experimental results (R² ≥ 0.9798). Total polyphenol yield and total flavonoid (TF) yield, as well as the antiradical power (ARP) of the extracts, were analysed. The use of high‐pressure high‐temperature technology resulted in obtaining extracts rich in polyphenols with high ARP. The highest total polyphenol (60.7 mg_GAE ) and TF (15.1 mg_CE ) yields were obtained at 150 °C for 270 min and 150 °C for 15 min, respectively. HPLC was employed to analyse phenolic compounds. Considerable quantities of single phenolic compounds were extracted. The highest yields of gallic acid, 5‐hydroxymethylfurfural, protocatechuic acid, catechin, vanillic acid, syringic acid, cumaric acid, trans‐resveratrol and quercetin (163.2, 20.0, 69.9, 420.0, 20.6, 603.0, 20.1, 42.4 and 117.1 mg per 100 g_DS, respectively) were found. ARP values were found between 8.45 and 52.17 μg_DPPH .