The Effects of Subcritical Water Treatment on Antioxidant Activity of Golden Oyster Mushroom

Subcritical water (SCW) extraction of golden oyster mushroom (GOM) was carried out at various temperatures (50, 100, 150, 200, 250, and 300 °C) for 10, 30, and 60 min, and the antioxidant and certain physiological activities of the extracts were evaluated. SCW treatment of GOM increased the antioxidant activity of the extracts. The SCW extraction of GOM at 250 °C for 60 min or 300 °C for 30 min showed relatively high levels of total phenolic content, 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, and reducing power. The β-glucan content was the highest when SCW extraction was carried at 200 °C for 60 min, while the highest 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radical scavenging activity occurred at 300 °C for 60 min. These results indicate that the temperature and time of SCW extraction significantly affect the antioxidant activity as well as the nutraceutical compound levels of GOM extracts.     

Identification of key aroma compounds generated from cysteine and carbohydrates under roasting conditions

 Application of the aroma extract dilution analysis to volatile fractions obtained from dry-heated (180  °C for 6 min on silica) mixtures of cysteine and ribose (I), glucose (II) or rhamnose (III) revealed the following compounds with the highest flavour dilution factors: 2-furfurylthiol (FFT) and 2-acetyl-2-thiazoline in I; 2-acetyl-2-thiazoline, 2-propionyl-2-thiazoline and FFT in II; 5-methyl-2-furfurylthiol, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, 2-acetyl-2-thiazoline, 2-propionyl-2-thiazoline and (Z)-2-propenyl-3,5-dimethylpyrazine in III. A comparison of the data with results of previous studies, in which the same mixtures had been reacted under aqueous conditions (145  °C, 20 min) revealed that the dry-heating process favoured the formation of the roasty, popcorn-like smelling 2-acetyl- and 2-propionyl-2-thiazoline as well as the potato-chip-like 2-ethyl-3,5-dimethylpyrazine and 2,3-diethyl-5-methylpyrazine in all three reaction systems. 2-Ethenyl- and (Z)-2-propenyl-3,5-dimethylpyrazine, both having an intense roast potato smell were, however, selectively formed in the presence of ribose or rhamnose, respectively. Based on quantitative data, pathways generating the latter two pyrazines via their 1-desoxyosones as key intermediates are discussed. Received: 11 March 1998     

Effect of Chitin as Coagulating Aid on Protein Yield, Composition and Functionality of Tomato Seed Protein Concentrates

The effectiveness of chitin as coagulating aid, protein coagulants and coagulation temperatures in recovering tomato seed proteins, and their effect on composition and emulsion properties of tomato seed protein concentrates (TSPC) were investigated. Citric acid, hydrochloric acid, or a mixture of citric acid and hydrochloric acid were used and chitin addition ranged from 0 to 1.0% (protein basis). Coagulation temperatures employed were 25°C, 60°C or 95°C. Samples with no chitin added resulted in significantly (P < 0.05) lower protein yields than samples with chitin addition. Ash content of the TSPC was significantly (P < 0.05) affected by chitin addition and coagulation temperature. Lowest crude fat content was obtained with citric acid at 25°C. Lowry protein and total nitrogen was highest without chitin addition. Samples coagulated at 25°C showed highest emulsion ability and emulsion stability. The least stable emulsions were produced with hydrochloric acid. Chitin addition did not affect emulsion properties.     

High-Pressure-Induced Gel of Sardine (Sardina pilchardus) Washed Mince as Affected by Pressure-Time-Temperature

Response surface methodology was used to determine how interactions of pressure (150–500 MPa), time (10–30 min) and temperature (0–75°C) affected gelling of sardine washed mince (2.5% NaCl) as compared with conventional heat processing at atmospheric pressure. The best conditions for optimum rheological parameters were pressure around 300 MPa, chilled temperature (< 10°C) and short processing times (10 min). Pressurizing considerably improved the rheological values of a mince which exhibited low gel-forming ability under conventional heat treatment.     

Effects of high pressure and temperature on buckwheat starch characteristics

Pressure-induced gelatinisation of buckwheat starch suspensions (25% w/w) was studied and compared to heat-induced gelatinisation. Starch suspensions were treated at increased pressure (200–600 MPa) or temperature (60–95 °C) for 10 min. The degree of gelatinisation and the temperature and pressure ranges of gelatinisation were determined using differential scanning calorimetry, changes in birefringence and pasting behaviour. Furthermore, the structural changes during gelatinisation were investigated using microscopy. The pressure-induced as well as the temperature-induced gelatinisation curves were sigmoid shaped. Gelatinisation occurred between 300 and 500 MPa or between 60 and 70 °C. Scanning electron microscopy images showed retention of the granular structure after treatment with 600 MPa. However, when heated at temperatures above 65 °C, the formation of a “sponge-like” structure was observed. Better preservation of the granular structure for pressure treatment compared to temperature treatment resulted in stronger gels for the former. Pre-treatment with pressure as well as temperature made the buckwheat starch granules more resistant to swelling and disintegration under the influence of additional heat.     

Processing of cauliflower by ohmic heating: influence of precooking on firmness

The feasibility of processing cauliflower by ohmic heating was investigated. Firstly, cauliflower florets were precooked in tap water at low temperatures (40–70 °C) for 0 to 60 min. A control sample was cooked at 95 °C for 5 min. No significant textural differences were found between samples treated at 40 or 50 °C and fresh samples, but the firmness of samples cooked above 60 °C decreased. The effect of precooking time was not found to be significant. Secondly, low temperature precooking was performed in salted water for 30 min and followed by ohmic heating (holding time 30 s at 135 °C). After ohmic heating, florets pretreated at low temperatures were firmer than control samples. The firmness of florets precooked at 40 °C or 50 °C was considerably increased (>300%) compared to those precooked at 95 °C. Low-temperature precooking increased the firmness of cauliflower subjected to ohmic heating. The experimental results show that ohmic heating combined with low-temperature precooking in saline solutions offers a viable solution to high temperature/short time sterilisation of cauliflower florets. © 1999 Society of Chemical Industry     

Formation of Volatile Compounds During Bacillus subtilis Fermentation of Soya Beans

The formation of volatile compounds during the Bacillus subtilis fermentation of cooked, roasted soya bean cotyledons was investigated. The materials examined were: dry roasted cotyledons; autoclaved, roasted cotyledons; and autoclaved, roasted cotyledons fermented for 18 h and 36 h at 35°C. Growth of B subtilis led to the formation of many volatile compounds. The volatile compounds formed in the largest amounts during fermentation were 3-hydroxy-2-butanone (acetoin), 2,5-dimethylpyrazine and trimethylpyrazine. Compounds present at concentrations exceeding their odour threshold values included nonanal, decanal, 1-octen-3-ol, butanedione, 3-hydroxy-2-butanone, 3-octanone, 2,5-dimethylpyrazine, 3,6-dimethyl-2-ethylpyrazine, 2-pentylfuran, dimethyl sulfide, benzaldehyde and 2-methoxyphenol. Compounds found in 18 h fermented cotyledons which were absent, or present in much lower concentrations, in roasted or autoclaved cotyledons included several aliphatic ketones, acetic acid, two aliphatic esters, several pyrazines, 2-pentylfuran, dimethyl sulphide, 2-methoxyphenol and trimethyloxazole. The total mass of volatile compounds present after 36 h incubation was less than half that present after 18 h. This was mainly due to the disappearance of 3-hydroxy-2-butanone, 2,5-dimethylpyrazine and 2,6-dimethylpyrazine. The biogenesis of the volatile compounds is discussed. © 1997 SCI.     

Effect of Temperature on the Serum Viscosity of Tomato Juice

Tomato juice was canned and exposed to processing temperatures of 82°C., 102°C and 112°C. Serum viscosity was measured after 30, 60, and 120 min at each temperature. Heat treatment affected serum viscosity. A temperature of 82°C applied for 2 hr resulted in a 17-30% loss of serum viscosity depending on the cultivar. Treatment at 112°C applied for 2 hr caused 67-82% loss, again depending on the cultivar.     

Ascertaining of Optimum Pyrolysis Conditions in Producing Refuse Tea Biochar as a Soil Amendment

Refused tea is a waste product of tea processing. Manufacturing of biochar from organic waste is an emerging technology where biochar can be used as a soil amendment for environmental remediation and carbon sequestration. As such the aim of this study was to determine the optimum pyrolysis conditions in producing refuse tea biochar for the said uses. Three refused tea samples were collected randomly from the bulk from tea processing factory in Gampola area of Sri Lanka and basic physical and proximate analysis were done. Initially, refused tea was packed tightly in the pyrolytic reactor which was designed to pyrolysis refused tea and pyrolysis was carried out by using five combinations of temperature (300, 350, 400, 450, 500 ^oC) and four retention times (15 min, 30 min, 45 min and 1 hour). The physical and chemical characteristics of biochar were analysed in line with the biochar quality standards proposed by International Biochar Initiatives (IBI). Results showed that the yield of biochar varied with the residence time for a given temperature treatment. The chemical, physical and morphological properties of biochar are largely influenced by the residence time for a given temperature treatment. Temperatures between 450^oC and 500^oC, and residence time between 45 and 60 minutes showed the highest biochar mass recovery. This research revealed that refuse tea can be effectively converted to biochar between 450 to 500 oC temperatures subjected to a residence time of 45 to 60 minutes. It also showed that higher volatilization rates at optimum temperature and residence time combination can be positively used for up scaling the pyrolysis reactor.     

Effects of High Hydrostatic Pressure on the Physical,Microbial, and Chemical Attributes of Oysters (Crassostrea virginica)

The change in the quality attributes (physical, microbial, and chemical) of oysters (Crassostrea virginica) after high hydrostatic pressure (HHP) treatment at 300 MPa at room temperature (RT, 25 °C) 300, 450, and 500 MPa at 0 °C for 2 min and control oysters without treatment were evaluated over 3 wk. The texture and tissue yield percentages of oysters HHP treated at 300 MPa, RT increased significantly (P < 0.05) compared to control. Aerobic and psychrotrophic bacteria in control oysters reached the spoilage point of 7 log CFU/g after 15 d. Coliform counts (log MPN/g) were low during storage with total and fecal coliforms less than 3.5 and 1.0. High pressure treated oysters at 500 MPa at 0 °C were significantly higher (P < 0.05) than oysters HHP treated at 300 MPa at 0 °C in lipid oxidation values. The highest pressure (500 MPa) treatment in this study, significantly (P < 0.05) decreased unsaturated fatty acid percentage compared to control. The glycogen content of control oysters at 3 wk was significantly higher (P < 0.05) when compared to HHP treated oysters [300 MPa, (RT); 450 MPa (0 °C); and 500 MPa (0 °C)]. HHP treatments of oysters were not significantly different in pH, percent salt extractable protein (SEP), and total lipid values compared to control. Based on our results, HHP prolongs the physical, microbial, and chemical quality of oysters.     

The effects of temperature on the retention and denaturation of protein in lucerne leaves subjected to mechanical dewatering

The effects of pretreatment temperature on the retention and denaturation of protein were studied in relation to moisture removal from lucerne forage subjected to mechanical pressing. Leaf samples were held for 5 min at a temperature between 40-100°C, then pressed. Although the protein concentration of the expressed juice decreased with increasing temperature, the amount of soluble protein lost in the expressed juice was fairly constant, amounting at most to only 4%. The maximum reduction in water content (76 ± 1%) was achieved by pressing after a treatment of 60-70°C. However, the protein retained in the residue was not denatured completely until the pretreatment temperature exceeded 80°C. At 60°C, with maximum water removal, only one-third of the protein became denatured; at 50°C, 80% of the maximum water removal was obtained with only 16% denaturation of retained protein.     

Decomposition of betacyanins and betaxanthins by heat and pH changes

Authors investigated the decomposition of the main beetroot colourings betanin and vulgaxanthin I as a function of temperature and pH value in acetate and citrate buffer solutions, in a temperature-range between 60 °C and 80 °C and pH range of 3.3–6.2. The temperature dependence of betain decomposition is characterized by a Q₁₀ value of 2.23 ± 0.45, and the reaction rate was doubled by reducing the pH value from 6.2 to 3.3 independent from the type of acid used. Also the interaction between temperature and pH value on colour decomposition was verified. Investigations were carried out at low oxygen content, and under this conditions the reaction was exactly described - considering the time interval of 20 min - by a linear function at 60 °C, pH value 3.3–6.2 and by an exponential function at 70 °C and 80 °C and pH 3.3–4.65. Activation energy for betain degradation is 77.5 ± 6.76 kJ/mol.     

A modified laboratory canning protocol for quality evaluation of dry bean (Phaseolus vulgaris L)

The effects of calcium (Ca²⁺) level in the soak water, blanch water and brine, blanching temperature, and total seed solids on dry bean canning quality were investigated to optimise a laboratory canning protocol. A linear increase in the Ca²⁺ level of soak water, blanch water and brine resulted in a linear decrease in hydration coefficient and percent washed drained weight but a linear increase in texture. Low Ca²⁺ level (10 mg kg⁻¹) reduced the hydration time for dry bean seed from 14 to 1 h. Blanching temperatures of 50, 70 and 88 °C had non‐significant effects on canning quality traits. Blanching for 30 min at 70 °C for black bean or at 88 °C for navy bean and pinto bean resulted in percent washed drained weight ≥ 60, as required by the Canada Agricultural Products Standards Act. Seed solids levels of 95–97 g per 300 × 407 (14 fl oz) can were sufficient to attain a percent washed drained weight of 60. It was confirmed that the thermal processing conditions (115.6 °C retort temperature, 45 min) used in this study were sufficient to achieve commercial sterility. The optimised lab protocol for evaluation of the canning quality of dry bean breeding lines is as follows. Seed containing 95 g of solids for pinto bean, 96 g for navy bean and 97 g for black bean is soaked in water for 30 min at 20 °C and blanched for 30 min at 70 °C for black bean and 88 °C for navy bean and pinto bean in water containing 10 mg kg⁻¹ of Ca²⁺. The seed is then transferred to a 300 × 407 can, filled with brine containing 10 mg kg⁻¹ of Ca²⁺, 1.3% (w/v) of NaCl and 1.6% (w/v) of sugar. The can is then sealed, processed in steam at 115.6 °C for 45 min and cooled at 20 °C for 20 min. Cans are stored for at least 2 weeks prior to quality evaluation of the canned product. Canning of dry bean seed according to this protocol results in precise estimation of canning quality traits, particularly percent washed drained weight. © 2000 Society of Chemical Industry     

Supercritical carbon dioxide extraction of astaxanthin and other carotenoids from the microalga Haematococcus pluvialis

Supercritical carbon dioxide extraction of astaxanthin and other carotenoids from Haematococcus pluvialis was carried out, for several experimental conditions, using a semi-continuous apparatus. The microalga was previously freeze-dried and ground with a ball mill. The effects of pressure (200 and 300 bar), temperature (40 and 60 °C), degree of crushing, as well as the use of ethanol as a co-solvent (10%) on the extraction efficiency were assessed. Organic solvent extractions, using acetone, were also carried out in a vortex, on ground cells mixed with very small glass beads. Supercritical extraction from the completely crushed alga was compared with acetone and the highest recovery of carotenoids (92%) was obtained at the pressure of 300 bar and the temperature of 60 °C, using ethanol as a co-solvent.The extraction recovery increased with the pressure at 60 °C. On the other hand, the increase in temperature, at 300 bar, led to a slight improvement. The main carotenoid of Haematococcus pluvialis is the esterified astaxanthin (about 75%). Other carotenoids present are lutein, astaxanthin (free), β-carotene and canthaxanthin. All of them were recovered through supercritical fluid extraction with values higher than 90%, with the exception of canthaxanthin (about 85%), at a pressure of 300 bar and a temperature of 60 °C.     

Volatile Compounds of the Wax Gourd (Benincasa hispida, Cogn) and a Wax Gourd Beverage

The volatile compounds of the wax gourd (Benincasa hispida, Cogn) and a wax gourd beverage were isolated by the Likens-Nickerson method and identified by Kovats indices and mass spectra. The major compounds identified in the gourds were E-2-hexenal, n-hexanal and n-hexyl formate; however, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, 2,3,5-trimethylprazine, 2-methylpyrazine, and 2-ethyl-5-methylpyrazine were the major compounds in the wax gourd beverage.     

From woody biomass waste to biocoke: influence of the proportion of different tree components

This paper assesses the feasibility of producing a metallurgical quality charcoal (biocoke) through slow high temperature pyrolysis of woody biomass. The samples used for the experiments were different types of olive wood biomass from southern Spain as well as eucalyptus trunks from Uruguay. The experiments were conducted in a two-step process: a pyrolysis semi-batch reaction at 750 °C and 3 °C/min heating rate, followed by a second step of thermal treatment at 900 °C of the pyrolysis vapours. The type of raw material used plays an important role with respect to the amount and quality of the different pyrolysis products. With the operating conditions used, high solid (24–26 wt%) and gas yields (43–54 wt%) were obtained. The solids obtained (biocoke) fulfil the requirements of good metallurgical reducers. However, leaves and bark are detrimental to biocoke quality and should be avoided. Pyrolysis gases are rich in CO and hydrogen, whereas pyrolysis liquids are mainly composed of water.     

Rice Bran Stabilization by Extrusion Cooking for Extraction of Edible Oil

An extrusion cooking procedure was developed which produces stabie rice bran which shows no significant increase in free fatty acid content for at least 30–60 days. In the optimum process, 500 kg/hr of 12 - 13% moisture bran was extruded at 130°C and held 3 min at 97 - 99°C before cooling. Stabilized bran contained 6 - 7% moisture and was in the form of small flakes with 88% larger than 0.7 mm (25 mesh). Energy required to extrude the bran was 0.07 - 0.08 kW-hr/lcg bran, and wear on the extrusion surface indicated a life of 500 hr for the cone and 1000 - 2000 hr for other wearing parts.     

Effects of High‐Hydrostatic Pressure on Inactivation of Human Norovirus and Physical and Sensory Characteristics of Oysters

The purpose of the study was to determine the effect of high‐hydrostatic pressure (HHP) on inactivation of human norovirus (HuNoV) in oysters and to evaluate organoleptic characteristics of oysters treated at pressure levels required for HuNoV inactivation. Genogroup I.1 (GI.1) or Genogroup II.4 (GII.4) HuNoV was inoculated into oysters and treated at 300 to 600 MPa at 25 and 0 °C for 2 min. After HHP, viral particles were extracted by porcine gastric mucin‐conjugated magnetic beads (PGM‐MBs) and viral RNA was quantified by real‐time RT‐PCR. Lower initial temperature (0 °C) significantly enhanced HHP inactivation of HuNoV compared to ambient temperature (25 °C; P < 0.05). HHP at 350 and 500 MPa at 0 °C could achieve more than 4 log₁₀ reduction of GII.4 and GI.1 HuNoV in oysters, respectively. HHP treatments did not significantly change color or texture of oyster tissue. A 1‐ to 5‐scale hedonic sensory evaluation on appearance, aroma, color, and overall acceptability showed that pressure‐treated oysters received significantly higher quality scores than the untreated control (P < 0.05). Elevated pressure levels at 450 and 500 MPa did not significantly affect scores compared to 300 MPa at 0 °C, indicating increasing pressure level did not affect sensory acceptability of oysters. Oysters treated at 0 °C had slightly lower acceptability than the group treated at room temperature on day 1 (P < 0.05), but after 1 wk storage, no significant difference in sensory attributes and consumer desirability was observed (P > 0.05).     

Effect of Various Pyrolysis Parameters on the Fragmentation Patterns of Peanut Oil

A simple and rapid pyrolysis-gas liquid chromatographic technique to quantitate the fragmentation pattern of a commercial peanut oil was developed. The oil was pyrolyzed at 300, 500, 700, 900, and 1100°C for 4, 10, and 16 sec. The optimum condition was determined by analyzing aliquots of the pyrolyzates by gas liquid chromatography and by quantitating data from 16 peaks. The operating parameters selected for optimum pyrolysis were 700°C for 10 sec under N₂ gas and 360 mm Hg partial pressure. Preliminary tests showed that this condition could be extended to other fats and oils.     

Effect of High Hydrostatic Pressure Combined with Moderate Heat to Inactivate Pressure‐Resistant Bacteria in Water‐Boiled Salted Duck

The objective of this work was to study the effect of high hydrostatic pressure combined with moderate heat to inactivate pressure‐resistant bacteria in water‐boiled salted duck meat (WBSDM), and to establish suitable procedures to improve the quality of WBSDM. The conditions (300 MPa/60 °C, 400 MPa/60 °C, and 500 MPa/50 °C) effectively inactivated the pressure‐resistant bacteria (Bacillus cereus and Staphylococcus warneri) in WBSDM. Although more pressure‐resistant than S. warneri, the above treatment conditions inactivated B. cereus more than 10⁷ CFU/mL in buffer, and more than 10⁶ CFU/g in WBSDM, and did not cause any changes in color, texture, or moisture content of products. The interaction between pressure and temperature is a more significant factor than only pressure in inactivating both B. cereus and S. warneri, the treatment of WBSDM at 400 MPa/ 60 °C/ 10 min is the most practical condition for postprocess of WBSDM after cooking.