Effect of high pressure homogenization (HPH) on microstructure and rheological properties of hazelnut milk

The effect of high pressure homogenization (HPH) on microstructure and rheological properties of hazelnut milks was investigated. Hazelnut milk samples were produced from cold pressed hazelnut cake and homogenized up to 150 MPa pressure. Microstructural and rheological properties of products, except temperature sweep, were greatly affected by HPH treatments. Homogenized samples showed significant reduction in particle size, which turned from bimodal and poly-disperse to monodisperse distributions. HPH decreased the consistency of products from 91.82 to 0.51 Pa.sⁿ and increased flow behavior index from 0.15 to 0.36. All samples showed higher values G′ than G″, which indicates that samples could be classified as soft-gel network, and hazelnut milk samples did not obey the Cox-Merz rule without multiplying angular frequency with shift factor. In conclusion, HPH can be used to reduce the consistency of samples and the friction loss, thus minimizing the amount of energy required to flow during processing and distribution.Industrial relevance.Vegetable based beverages are available at any supermarket as an alternative to dairy products with an increasing consumer acceptance. Between these beverages hazelnut milk samples are the most noteworthy products due to important role in human nutrition and health, and moreover due to well accepted and widely consumed product. Due to its composition, hazelnut milks have very high consistency, and therefore, the energy consumption for processing and handling is too high. In this research, the high pressure homogenization (HPH) technology was successfully proposed to be used for improving microstructural properties, and hence reducing its consistency. The energy consumption during processing and distribution can be minimized by reducing the consistency and friction losses of product.     

Detection of the adulteration of olive oils by solid phase microextraction and multidimensional gas chromatography

The presence or absence of filbertone in 21 admixtures of olive oil with virgin and refined hazelnut oils obtained using various processing techniques from different varieties and geographical origins was evaluated by solid phase microextraction and multidimensional gas chromatography (SPME–MDGC). The obtained results showed that the sensitivity achievable with the proposed procedure was enough to detect filbertone and, hence, to establish the adulteration of olive oil of different varieties with virgin hazelnut oils in percentages of up to 7%. The very low concentrations in which filbertone occurs in some refined hazelnut oils made difficult its detection in specific admixtures. In any case, the minimum adulteration level to be detected depends on the oil varieties present in the adulterated samples. In the present study, the presence of R- and S-enantiomers of filbertone could be occasionally detected in olive oils adulterated with 10–20% of refined hazelnut oil.     

Characterisation of Chilean hazelnut (Gevuina avellana) tissues: light microscopy and cell wall polysaccharides

By applying several differential staining techniques and light microscopy, the structure and composition of Chilean hazelnut (Gevuina avellana) seeds were analysed. The structure of the G avellana seed is very simple, with a thin, heavily lignified seed coat and two voluminous cotyledons. The embryo food reserves are uniformly distributed over the cotyledon cells. The cell wall polysaccharides were recovered from the alcohol‐insoluble residue by mild treatment with warm chlorite solution and sequential extraction with alkali solutions of increasing concentration. FT‐IR spectra in the 1200–850 cm^?1 region were used together with chemometric techniques to distinguish the hemicellulosic and pectic polysaccharides in the extracts. The most abundant extracts were fractionated by graded precipitation in ethanol. A xyloglucan was identified by ¹H and ¹³C NMR as the major hemicellulosic polysaccharide, with a sugar composition of 4Glc:3.5Xyl:1Gal:0.5Fuc. The hazelnut cell walls are composed of equivalent amounts of pectic polysaccharides, xyloglucans and cellulose. © 2003 Society of Chemical Industry     

Nutritional composition and antioxidant activity in hazelnut shells from US‐grown cultivars

The hard shell of a hazelnut is a major waste of the hazelnut industry. The chemical composition, phenolic compounds (total phenolics, tannins and condensed tannins), antioxidant activity (DPPH and ABTS free‐radical scavenging assays), and the relationships between phenolic compounds and antioxidant activities of the hazelnut shells from twelve US grown cultivars were investigated to for potential commercial development. Crude fibre accounted for over 85% of total carbohydrate. The shells contained high concentrations of phenolic compounds. Concentrations of phenolic constituents and ABTS^?+ ‐scavenging capacities were significantly higher (P > 0.05) in the Oregon cultivars than their Nebraska counterparts. There were significant positive correlations between ABTS^?+ scavenging capacities and the phenolic compounds, whereas DPPH^? ‐scavenging capacity demonstrated a weak negative correlation with ABTS^?+ scavenging capacity and the phenolics. The results suggest that hazelnut hard shell may serve as a potential source of natural antioxidants for food applications.     

MALDI-based identification of stable hazelnut protein derived tryptic marker peptides

Food allergy is an important health problem especially in industrialised countries. Tree nuts, among which are hazelnuts (Corylus avellana), are typically causing serious and life-threatening symptoms in sensitive subjects. Hazelnut is used as a food ingredient in pastry, confectionary products, ice cream and meat products, therefore undeclared hazelnut can be often present as a cross-contaminant representing a threat for allergic consumers. Mass spectrometric techniques are used for the detection of food allergens in processed foods, but limited information regarding stable tryptic peptide markers for hazelnut is available. The aim of this study was to detect stable peptide markers from modified hazelnut protein through the Maillard reaction and oxidation in a buffered solution. Peptides ³⁹⁵Gly-Arg⁴⁰³ from Cor a 11 and ²⁰⁹Gln-Arg²¹⁷, ³⁵¹Ile-Arg³⁶³, ⁴⁶⁴Ala-Arg⁴⁷⁸ and ⁴⁰¹Val-Arg⁴¹⁷ from Cor a 9 hazelnut allergens proved to be the most stable and could be detected and confirmed with high scores in most of the modified samples. The identified peptides can be further used as analytical targets for the development of more robust quantitative methods for hazelnut detection in processed foods.     

Aflatoxin levels in raw and processed hazelnuts in Turkey

Aflatoxin levels in hazelnut samples obtained from exporter companies were monitored over a 3-year period. A total of 3188 samples of raw and processed hazelnuts were analysed using an HPLC method. The total aflatoxin content of the contaminated samples was in the range of 0.02–78.98?µg?kg^?1 for hazelnut kernels, 0.07–43.59?µg?kg^?1 for roasted hazelnut kernels, 0.02–39.17?µg?kg^?1 for roasted sliced hazelnut kernels, and 0.02–11.20?µg?kg^?1 for hazelnut purees, respectively, showing that the variations of aflatoxin contamination were very high. The results of aflatoxin analysis revealed that the aflatoxin contamination in the hazelnut samples was at a tolerable level. A total of 3147 samples were contaminated with aflatoxins, although below the legal limits. However, the aflatoxin contents of 41 samples exceeded the legal limits. Therefore, aflatoxin contents of hazelnuts should be monitored regularly to minimise the risk of aflatoxin hazard, and pre- and post-harvest strategies should be developed to prevent aflatoxin formation.     

Spectrometric determination of iron and copper in vegetable oils after separation with Schiff base impregnated silica gel column: A simple approach for eliminating the high organic matrix

A simple solid‐phase extraction method has been described for the separation of Fe(III) and Cu(II) from liquid vegetable oils using N,N′‐bis(4‐methoxy salicylidene) ethylenediamine impregnated silica gel and the determination of these ions. The experimental parameters that affect the separation/preconcentration of ions were investigated by batch and column methods prior to the determination by flame atomic absorption spectrometry. Fe(III) and Cu(II) ions in 20.0 g portion of oil samples can be quantitatively sorbed and then eluted completely with 5.0 mL of 2.0 mol L^?1 HNO₃. Limits of detection were calculated as 22.8 and 13.9 μg kg^?1 for Fe(III) and Cu(II), respectively. The repetition of the suggested method was checked by finding relative standard deviation for five repeated analyses, which was 1.5% for Fe(III) and 0.1% for Cu(II). Applicability of the method was controlled with spiked and unspiked sunflower, corn, canola, olive, soya and hazelnut oils.     

东北红豆杉枝叶中紫杉醇和10-脱乙酰巴卡亭的分离纯化及检测

目的用HPLC法对东北红豆杉枝叶中的紫杉醇和10-脱乙酰巴卡亭(10-DAB)进行分离、纯化并对其进行检测。方法采用提取的办法从红豆杉枝叶中粗提紫杉醇和10-DAB;用硅胶色谱柱对粗提物进行分离纯化并进行重结晶;用HPLC法对纯化物进行检测。结果建立了HPLC法,对紫杉醇和10-DAB进行分离、纯化及检测。结论方法简便、准确度高、重现性好。     

Utilization of interesterified oil blends in the production of frankfurters

Ten treatments of frankfurters were produced with interesterified oil and oil blends (palm oil, palm stearin, cottonseed oil, hazelnut oil and their mixtures) and were compared to control, produced with all animal fat. Addition of interesterified oil and oil blends affected (p < 0.05) the moisture and fat content and pH values of frankfurters. According to the colour measurements, the brightness value (L^∗) of most of the samples with interesterified oil and oil blends were higher (p < 0.05) than the control. The fatty acid composition of frankfurters was modified. The PUFA/SFA values of frankfurters were increased due to the presence of interesterified oil and oil blends in the formulation. Frankfurters with 100% interesterified cottonseed oil or with interesterified oil blends with 66.6% and 83.4% cottonseed oil had PUFA/SFA ratio higher than 0.4 and are considered better than all others from the health point of view. Frankfurters produced with 100% interesterified cottonseed and hazelnut oil or with interesterified hazelnut oil blends had the same (p > 0.05) scores for sensory attributes with the control, while all other treatments were also acceptable.     

Lipolytic activity of Trichothecium roseum on hazelnut

Trichothecium roseum is a mould which grows on hazelnut after harvesting. It produces lipase enzyme which hydrolyses fat to produce free fatty acids (FFA) and partial glycerides. Free fatty acid content (which causes bitterness) is an important criterion, determining the quality and taste of hazelnut. The lipase production characteristics ofT. roseum have been investigated on agar and hazelnut in this study. Trichothecium roseum -inoculated hazelnuts have been stored at 25°C at 90%, 85% and 80% relative humidity. Free fatty acids as a percentage of the total fat content were found to be 1·6%, 1·4% and 1·4% respectively. Free fatty acids forT. roseum -inoculated hazelnut whose water content had been increased by water addition, was found to be 2% after 4 days, and 25% after 28 days storage. This is due to rapid hydrolysis under this condition. Partial glycerides were also observed after 4 days of storage.     

Partial purification and characterization of proteases from Norway lobster (Nephrops norvegicus) and their role in the phenolase activation process

Proteolytic activity in Norway lobster (Nephrops norvegicus) was studied. An improved separation and partial purification of the three proteases (designated as proteases I, II and III) was achieved from Norway lobster heads by a combination of acetone precipitation and DEAE-Sepharose CL-6B column chromatography.The purification achieved was 63-, 25- and 217-fold at pH 8.2, and 40-, 25- and 160-fold at pH 6.4 for protease I, II and III, respectively.With casein as substrate, protease III was most active at pH 8.2, whilst proteases I and II showed activity over a wide range of pH.Protease III was characterized as an alkaline Zn-serine protease as it was strongly inhibited by PMSF, soybean trypsin inhibitor, Co²⁺, Mn²⁺ and 1–10 phenanthroline. Protease I was strongly inhibited by p-benzoquinone, iodo-acetamide, heavy metals (Ag⁺, Cu²⁺) and 1–10 phenanthroline and was thus characterized as a Zn-thiol protease. Protease II was also inhibited by the same inhibitors as protease I (but to a lesser extent) and was characterized as a thiol protease.The molecular weights were determined to be 22.5, 45 and 42.5 kDa (with activity at 18 kDa) for proteases I, II and III, respectively.It was found that protease III activates phenolase at pH 8.2, whilst proteases II and I can activate phenolase at both pH 6.7 and 8.2.     

Occurrence of biogenic amines in Doubanjiang and Tofu

This study was performed to analyze biogenic amine contents and other parameters in doubanjiang and tofu. Through this study, it was found that doubanjiang contained considerably large amounts of most biogenic amines (>30 mg/kg of β-phenylethylamine in particular), and tofu had a relatively high level of spermidine (>20 mg/ kg). Therefore, the amounts of biogenic amines in the foods seem to be occasionally beyond the safe level for human consumption. Meanwhile, the biogenic amine contents in doubanjiang showed a good relationship with salt content (R²=0.89). The spermidine content in tofu samples was closely related to that in soybean, the raw material of tofu. There also appeared to be a good relationship (R²=0.82) between the biogenic amine contents and total plate counts in doubanjiang, but not in tofu. Most strains from the foods were capable of producing biogenic amines, and the identification revealed that bacterial ability to produce biogenic amines was determined at the level of strains rather than species. Taken together, it seems that biogenic amine contents in doubanjiang are mainly affected by fermentation processes, whereas those in tofu are primarily affected by raw materials.     

Using <Superscript>1</Superscript>H and <Superscript>13</Superscript>C NMR techniques and artificial neural networks to detect the adulteration of olive oil with hazelnut oil

The lack of any official analytical method to detect the adulteration of olive oil with a low percentage of hazelnut oil is explained by the similarities in the chemical compositions of both kinds of oils. To counter this problem, an artificial neural network based on ¹H-NMR and ¹³C-NMR data has been developed to detect olive oil adulteration, and the results from this ANN are presented here. A training set consisting of hazelnut oils, pure olive oils, and olive oils blended with 2–20% hazelnut oils was used to design and train a multilayer perceptron with 100% correct classifications. This mathematical model was also validated using an external validation set of blend samples (3–15%) and genuine samples. The detection limit of the model was around 8%.     

Increasing espresso coffee brew antioxidant capacity using phenolic extract recovered from hazelnut skin waste

The simultaneous consumption of different classes of phytochemical antioxidants in the diet can result in more beneficial effects than when consumed alone. In the present study, the in vitro and in vivo antioxidative effects of espresso coffee brew (EC) (rich in chlorogenic acids) with added crude hazelnut skin phenolic extract (HSPE) from hazelnut skin waste (rich in flavonoids) were studied. Both post-brewing and pre-brewing phenolic-enriched espresso coffees (PE-ECs) were analysed for total phenols and screened for their in vitro antiradical ability. Moreover, the in vivo biological effect on the antioxidant potential of plasma in rats was evaluated. The PE-ECs showed increased both in vitro and in vivo antiradical activity proportional to the added HSPE. The in vivo experiments suggested that HSPE was much more antioxidant active than the phenolic fraction naturally contained in EC. Moreover, evidence of possible synergic effects of EC and HSPE phenolics was observed in vivo.     

Effect of moisture on salmonella spp. heat resistance in cocoa and hazelnut shells

The heat resistance of food-poisoning outbreak and non-outbreak associated strains of Salmonella (S. Enteritidis, S. Montevideo, S. Napoli, S. Oranienburg, S. Poona, S. Senftenberg and S. Typhimurium) was established in confectionery-related materials such as crushed cocoa bean and hazelnut shells at low moisture contents (≤ 4% w/w). The two most heat resistant strains in cocoa and hazelnut shells at ca. 4% w/w moisture were S. Oranienburg and S. Enteritidis PT30. Both strains were associated with outbreaks from dried materials. Their D_100°C values were ca. 2.5 min in crushed cocoa bean shells and 7–11 min in crushed hazelnut shells. Addition of moisture to ca. 7% w/w markedly reduced D-values (D_80°C of 2–4.5 min) for both strains in the two matrices.     

Response surfaces of hazelnut oil yield in supercritical carbon dioxide

Response Surface Methodology was used to determine the effects of solvent flow rate (1, 3 and 5 g/min), pressure (300, 375 and 450 bar) and temperature (40, 50 and 60 °C) on hazelnut oil yield in supercritical carbon dioxide (SC-CO₂). Oil yield was represented by a second order response surface equation (R²=0.997) using Box-Bhenken design of experiments. Oil yield increased with increasing SC-CO₂ flow rate, pressure and temperature. The maximum oil yield was predicted from the response surface equation as 0.19 g oil/g hazelnut (34% of initial oil) when 4 g hazelnut particles (particle diameter<0.85 mm) were extracted with 5 g/min SC-CO₂ flow rate at 450 bar, and 60 °C for 10 min. Total extraction time at these conditions was predicted to be 35 min.     

The detection of the presence of hazelnut oil in olive oil by free and esterified sterols

Genuine olive and hazelnut oils from diverse geographical origins, as single varieties and blends, were mixed at different percentages and analysed by the method based on the quantification of free and esterified sterols. Two formulas based on three sterols (Campesterol, Δ⁷-stigmastenol and Δ⁷-avenasterol) together with empirical decision rules were able to detect the presence of hazelnut oil in olive oil when the percentage of the former was more than 6–8%, although this figure was much lower in the most of the adulterations. Results of univariate and multivariate statistical procedures based on the analysis of 116 samples are presented in support of the method efficiency.     

Effect of α‐tocopherol and α‐tocotrienol on the performance of Chilean hazelnut oil (Gevuina avellana Mol) at high temperature

The high temperature antioxidant efficiency of α‐tocopherol, α‐tocotrienol and a mixture of both on hazelnut oil were evaluated. Crude hazelnut oil (HZO), crude hazelnut oil treated with alumina (THZO), as well as three samples of THZO to which 150 mg kg^?1 of α‐tocopherol, 140 mg kg^?1 of α‐tocotrienol or a mixture containing 70 mg kg^?1 of α‐tocopherol and 70 mg kg^?1 of α‐tocotrienol, were added and submitted to thermal treatment at 180°C for 18 h. The addition of tocols to THZO decreased the formation of polar compounds and increased its oxidative stability in all the systems studied. However, α‐tocopherol showed a higher antioxidant capacity than α‐tocotrienol at high temperature. In addition, α‐tocotrienol showed a more rapid degradation rate than α‐tocopherol under the conditions studied. Copyright © 2004 Society of Chemical Industry     

Correction for seed-phosphorus effects in L-value determinations

Measurements of the specific activity of plants grown in ³²P-labelled soils have frequently been used to estimate soil labile phosphorus (L-values). It is usually assumed that the plant-P uptake is totally derived from soil-P. The contribution of seed-P to plant-P uptake and L-values is seldom considered. This paper describes results of an experiment which measured the effects of seed-P on L-values and how correction for seed-P effects may be made when only the tops of plants are analysed. L-values were obtained from three harvests of ryegrass grown in three soils of very low, low and medium P status (soils I, II and III), containing 4, 14 and 37 mg initial NaHCO₃-soluble P kg^?1 soil, and supplied with increasing amounts of added P. Ryegrass, supplied with increasing amounts of ³²P-labelled ³¹P, was simultaneously grown in P-free sand, under identical experimental conditions to the soil-grown plants. The seed-P in the tops of the sand-grown plants, at increasing dry matter yields, was calculated and used to make appropriate corrections for seed-P in the tops of soil-grown plants. After correction for seed-P effects, L-values were reduced at the first harvest by 69% in soil I, 18% in soil II and 10% in soil III, at the second harvest by 27, 11 and 5%, and at the third harvest by 18, 6 and 4%, respectively. Increasing the amount of added P to soil-grown plants also caused some reduction in L-values in soil I but the effect was much less in soils II and III. The reduction in L-values at higher rates of added P in soil I was probably a result of increased P uptake diluting the effects of seed-P. In the other two soils, plant-P uptake was much greater, at all rates of added P, and this effect was very small.     

HPLC–MS identification of phenols in hazelnut (Corylus avellana L.) kernels

In whole hazelnut kernels, as the main product of hazelnut (Corylus avellana L.), phenols were analysed in 20 hazelnut cultivars by high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS). Twenty-three compounds from different phenolic groups were detected, and 15 of them were identified. In hazelnut kernels, these substances were detected: nine flavan-3-ols, two benzoic acids (gallic and protocatechuic acid), three flavonols and phloretin glycoside. Total phenol concentrations ranged from 70 to 478 mg gallic acid equivalents per kg hazelnut kernels. A high content level of total phenols was observed in the ‘Tonda Gentile delle Langhe’ and ‘Lewis’ cultivars, which was followed by the ‘Corabel’, ‘Fertile de Coutard’, ‘Daria’ and ‘Tonda Gentile Romana’ cultivars. Similarly, the highest antioxidative activity, measured by employing DPPH-antiradical assay, was also found in the ‘Tonda Gentile delle Langhe’ cultivar, followed by the ‘Fertile de Coutard’.