Showing papers in "Journal of Food Processing and Preservation in 2006"

Influence of roasting conditions on volatile flavor of roasted malaysian cocoa beans

Abstract: In this study, commercial Malaysian cocoa beans (SMC1A) were roasted in a forced airflow-drying oven for 20, 30, 40 and 50 min at 120, 130, 140, 150, 160 and 170C. The products were evaluated for flavor compounds and sensory evaluation (as dark chocolate). The volatile fraction was isolated using the combined steam distillation–extraction procedure and was identified by gas chromatography–mass spectrometry. A quantitative descriptive analysis was used to evaluate the flavor intensity of the chocolates using a 9-point rating scale for selected flavor attributes, namely astringency, bitter taste, sour taste, cocoa and burnt. Panelists were asked to smell and taste the sample against a standard chocolate. It was found that there were significant differences in flavor compounds between the different conditions of roasting. The main flavoring compounds identified composed of aliphatic and alicyclic groups such as alcohol and ester, and heterocyclic groups such as pyrazine and aldehyde. A total of 19 volatile major components were identified: nine pyrazines (2,5-dimethyl-, 2,3-dimethyl-, 2-ethyl-6-methyl-, trimethyl-, 3-ethyl-2,5-dimethyl-, tetramethyl-, 2-ethenyl-6-methyl- and 3,5-dimethyl-2-methylpyrazine); five aldehydes (5-methyl-2-phenyl-2-hexenal, benzaldehyde, benzalacetaldehyde and α-ethyliden-benzenacetaldehyde); one methyl ketone (2-nonanone); two alcohols (linalool and 2-heptanol); and two esters (4-ethylphenyl acetate and 2-phenylethyl acetate). Based on the flavor profile of the compounds identified, an optimum production of the major flavoring compounds such as pyrazine, aldehyde, ketone, alcohol and ester occurred at 160C for 30 min of roasting. Trimethylpyrazine and tetramethylpyrazine compounds together with 5-methyl-2-phenyl-2-hexanal were found to be good indicators for the evaluation of the roasting process. However, based on chocolate evaluation, the best roasting temperature was 150C for 30 min, which gave the lowest astringency and at the same time gave the lowest bitter taste and low level of sour and burnt tastes. At 150C roasting temperature, the desirable cocoa flavor was at its optimum. Correlation coefficients among certain volatile flavor and sensory characteristics of cocoa beans and dark chocolate were significant (P < 0.05).

Evaluation of processing tomatoes from two consecutive growing seasons: quality attributes, peelability and yield

Abstract: Peelability is an important quality parameter in the selection of tomato cultivars (cvs.) for whole peeled and dice processing. Six processing tomato cvs. were evaluated in two consecutive years to examine the effects of cv., maturity and physical attributes on peelability and yield. Physical attributes of the raw tomatoes (size, weight, pericarp wall thickness, color) and processed paste quality (pH, titratable acidity, soluble solids, Bostwick consistency, serum viscosity, color) were determined. Large variations in physical attributes and paste quality were observed in selected tomato cvs. and maturities. In general, most of the attributes indicative of paste quality were more desirable at the less mature (e.g., pink) stage and declined with maturity. Statistical analysis suggests that there were significant differences in percentage of peeled tomatoes, peel index, and yields of whole peeled and diced tomatoes between two consecutive growing years.

Extraction yield of soluble protein and microstructure of soybean affected by microwave heating

Abstract: A laboratory-scale microwave (MW)-assisted extraction system was constructed and compared with a conventional shaking water bath regarding the extraction of soluble proteins in soybeans. Dynamic reaction was monitored by response surface methodology in the MW-assisted extraction system. The yield of soluble protein increased until either temperature (T) or water/solid (W/S) ratio reached an optimum point (60.1C, 12.6 mL/g), and then decreased with further increase of Tor W/S ratio. In addition, the yield of soluble protein increased with time within a range of 30 min, and no critical point was observed. The molecular mass of soluble protein was distributed from 19.3 to 81.3 kDa estimated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. Scanning electron microscopy showed the destruction of the microstructure of soybean cells, which increased the extraction of soluble soy protein.

The effects of different initial lactobacillus plantarum concentrations on some properties of fermented carrot juice

Abstract: Carrot juice (Daucus carota L.) is one of the most popular vegetable juices and represents a rich source of natural β-carotene. Vegetable juices are available either fermented or not fermented. With the production of lactofermented juices, carrot juices are microbiologically stable, delicious and potentially provide high nutritional value. In this study, Refik Saydam Kulfur Kolleksiyanu (RSKK) 1602 Lactobacillus plantarum is used as a starter culture in carrot mash. Sensory evaluation demonstrated that an initial bacteria concentration of 3 × 10 5 cfu/g mash resulted in the most preferred fermented carrot juice. The acidity of the fermented carrot juice can be adjusted by altering the population of the starter RSKK 1602 L. plantarum culture and the 15-16 h of fermentation time. A modified Gompertz equation was selected to describe the growth curve of RSKK 1602 L. plantarum in carrot mash.

Soaking, boiling and antinutritional factors in pigeon peas (cajanus cajan) and cowpeas (vigna unguiculata)

Abstract: The effects of soaking, boiling and combination of soaking and boiling at various treatment levels on the detoxification of trypsin inhibitor, cyanogenic glycoside, hemagglutinin, alkaloids and tannin in pigeon pea and vegetable cowpea were studied. Soaking was carried out for 6, 12 and 18 h while boiling was carried out for 40, 60 and 80 min. In combined soaking and boiling method, the beans were soaked for 12 h and then boiled for 40, 60 and 80 min. The results showed that the most effective method of detoxifying any of the toxicants was soaking for 12 h and boiling for 80 min. This method was able to reduce the trypsin inhibitor from 12.45 to 2.59 TUI/mg in pigeon pea and 25.60 to 3.20 TUI/mg in vegetable cowpea. The method also reduced the hemagglutinin content from 27.88 HU/mg to nil and 49.50 to 9.52 HU/mg; the cyanogenic glycoside from 40.50 mg/kg to nil and 83.81 to 5.06 mg/kg; alkaloids from 0.26 to 0.16% and 9.61 to 0.50%; and tannin from 1.60% to nil and from 3.42 to 1.28% in pigeon pea and vegetable cowpea, respectively. This method was found to be more potent in eliminating any of the toxicants rather than soaking or boiling alone.

Compositional changes of strawberry due to dehydration, cold storage and freezing–thawing processes

Abstract: Strawberry is an excellent source of food ingredients, although compositional changes might occur in improperly controlled processing, affecting product quality. In this article, changes in sugar composition (glucose, fructose and sucrose), citric acid, water and total soluble content, as induced by partial dehydration and freezing-thawing processes, were analyzed in strawberries (var. Camarosa). Osmotic dehydration (OD) with 65 °Brix sucrose solution, air drying (AD) at 45C, or combined treatments (OD-AD) were applied to reduce strawberries' water content to 70-85%. Fresh and dehydrated samples were frozen (-40C, 24 h) and stored (-18C, 30 and 180 days). All samples processed by OD and OD-AD showed a significant sugar gain, and depending on the dehydration treatment, total or partial sucrose hydrolysis was observed. Dehydration treatments caused small losses of citric acid. During the freezing-thawing process, drip loss and enzymatic action also cause changes in sugar concentration, especially in OD-treated samples.

Kinetics of osmotic dehydration of mango

Abstract: The effects of sucrose syrup concentration (40-70 g/100-g solution) and temperature (40-90C) on water loss and sucrose uptake by mango mesocarp slices during osmotic dehydration were investigated. The effective diffusivities for mass transfer were determined using the slope method based on the Fickian diffusion model. Water loss and sucrose uptake were proportional to the square root of osmotic contact time, implying that the process is Fickian. The specific mass transfer rate constants and effective diffusivities (D e ), derived from Fick's unsteady-state diffusion equation, increased with temperature and sucrose syrup concentration. D e values for water loss and sucrose uptake, which ranged between 2.59×10 -6 to 5.12×10 -6 m 2 /h and 1.70 x 10 -6 to 4.14 x 10 -6 m 2 /h, respectively, were related to absolute temperature using an Arrhenius-type relationship. The activation energies, which fell in the range previously reported for diffusion-controlled processes, increased with sucrose syrup concentration and varied from 9.74 to15.16 KJ/mol.

Extruded corn meal and whey protein concentrate: effect of particle size

Abstract: Blends of whey protein concentrate (WPC) and corn meal, which were separated into four particle fractions (residual on a #30 screen, #40 screen, #60 screen and through a #60 screen), were extruded at two moisture conditions (23 and 28%) to determine the effects of particle size on the extrudate properties. Smaller particle size fractions exhibited increased solubility and significantly higher viscosity both with and without added protein. When WPC was added to the corn meal, a large reduction in paste viscosity was observed regardless of the particle size. The blend with similar particle size distributions of corn meal and WPC had a significantly higher viscosity than the other blends. The expansion ratio, porosity and breaking strength of this blend, when extruded at the lower moisture content, were improved to the extent that they behaved similarly to extrudate made from corn meal alone.

Assessing lycopene content in california processing tomatoes

Abstract: Tomatoes constitute the main source of lycopene in the U.S. diet. Growing interest in the potential health-protective role of lycopene is bringing attention to the content of lycopene in tomatoes. A wide range of lycopene content (55–181 mg/kg) was observed in juice prepared from selected cultivars of tomatoes grown in nine California counties. A comparison of cultivars H 8892, H 9665 and Halley 3155 grown in Colusa, Fresno, San Joaquin and Yolo counties during three seasons concludes that mean lycopene concentrations were significantly greater (P < 0.01) in 2000 (106 mg/kg) than in 1999 (101 mg/kg) and 2001 (88 mg/kg). An evaluation of nine processing tomato cultivars harvested in one season on four separate dates indicated that lycopene concentration of tomatoes decreases with maturation on the plant. Lycopene concentration of tomatoes is dependent on the growing season, location, cultivar and maturity.

Fermentation of cashew (anacardium occidentale l.) “apple” into wine

Abstract: Cashew apple is considered as a waste in cashew nut processing industry. An undistilled alcoholic beverage (wine) was prepared by fermenting cashew apple juice with wine yeast, Saccharomyces cerevisiae var. bayanus. The wine was slightly yellowish, acidic in taste (titratable acidity [1.21 ± 0.0 g tartaric acid/100 mL]), high in tannin (1.9 ± 0.22 mg/100 mL) and low in alcohol (7%) concentration. Although sensory evaluation rated the cashew apple wine as quite acceptable as an alcoholic beverage, significant differences (P < 0.01) exist between the cashew wine and the commercial grape wine particularly in taste, aroma, flavor and aftertaste because of probably high tannin content in the cashew wine.

Characteristics of tigernut (cyperus esculentus) tubers and their performance in the production of a milky drink

Abstract: This article reports the effect of site and variety on some physicochemical characteristics of tigernuts (Cyperus esculentus) and consequently on its milk production. Two varieties (black and brown) from three different sites (Guily, Meme and Mayo-Oulo) in the Far North Province of Cameroon and three milk-processing conditions (grain size, soaking temperatures and grinding time) were assessed in the study. Results show that site and variety had a significant influence on the chemical composition of the tuber and its oil. The sample with the best overall performance in terms of its contents of proteins, lipids, ash, total sugars, saponification values and iodine values was the brown variety of tubers from Meme. Water absorption is at its maximum between 80 and 100C and for a period of 5 h. For temperatures lower than this, water absorption is slower. Extraction is influenced by soaking temperature, grain size and grinding time. Except for proteins, grinding time and temperature of soaking reduce significantly the different parameters analyzed. Thus, in terms of performance, milk extracted from the largest tubers soaked at 60C and ground for 20 min is the best condition for extraction. At this temperature, the maximum quantity of proteins is extracted.

EFFECT OF pH AND ASCORBIC ACID ON HIGH HYDROSTATIC PRESSURE-PROCESSED MANGO PUREE

Abstract: Mango puree containing ascorbic acid (AA) (500 ppm) standardized at low pH (3.5) with phosphoric acid and inoculated or noninoculated with Saccharomyces cerevisiae was treated at high pressure (207, 345, 483 and 552 MPa) for selected times. High hydrostatic pressure (HHP)-processed (552 MPa/5 min) standardized mango puree (SMP) was stored at 3C for 1 month and periodically analyzed for color, residual polyphenoloxidase (PPO) activity and microbial load. The remaining PPO activity average in SMP, after HHP processing at 207, 345, 483 and 552 MPa, at all times, was 35.8 ± 6, 21.5 ± 13.2, 46.8 ± 53.2 and 61.8 ± 5.8% PPO activity units, respectively. The D(207) values of 8.5 and 7.2 min for total count and yeasts were observed, respectively, after 207 MPa of pressure. A log reduction of 1.62 and 1.35 was observed after applying 345 MPa of pressure (2 s) for total count and yeasts, respectively. However, no microbial growth (<10 cfu/g) was observed after applying 483 or 552 MPa at any time. The addition of AA and the standardization at pH 3.5 reduced the rate of browning during storage.

Peelability and yield of processing tomatoes by steam or lye

Abstract: Approximately 25% of the processed tomatoes grown in California are made into value-added foods such as whole peeled and diced tomatoes. Peel removal is the first step in this process, and it must be optimized for both quality and yield. The effect of peeling conditions on tomato cultivars Halley 3155 and Heinz 8892 (H 8892) was evaluated. Considerable texture loss results from peeling; however, firmness was greater for cv. Halley 3155 than for cv. H 8892 regardless of peeling conditions utilized. Peeling under low steam pressures (12 psig) was insufficient to adequately peel either cultivar. While high pressure steam (18 psig) was more efficient at peel removal, increasing vacuum level from 20 in. to 24 in. did not improve peelability of either cultivar. Because cultivar affected peelability and yield, specific tomato cultivars should be evaluated and directed to either paste or whole peeled and diced tomatoes as appropriate.

Extrusion cooking of rice : Effect of amylose content and barrel temperature on product profile

Abstract: The effect of amylose content (5.0–28.6%) of rice and barrel temperature (80–120C) on extrusion system parameters torque and net specific mechanical energy and extrudate characteristics extrudate bulk density (ED), water solubility index, expansion ratio (ER) and Warner–Bratzler shear stress were studied using a twin-screw extruder. The feed rate (15 kgh 1), moisture content (20.0% ± 0.2) of feed and the screw speed (400 rpm) were kept constant. ED and ER of the product suggested that a barrel temperature of 120C was desirable to generate an expanded extrudate rice product from low-amylose rice cultivar. Experimental data on system parameters and extrudate characteristics fit to second-degree polynomial regression equations (r ≥ 0.904, P ≤ 0.01) with the amylose content of rice and barrel temperature of the extruder.

Processing of foxtail millet for improved nutrient availability

Abstract: Foxtail millet grains were soaked in distilled water (1:5, w/v) for 12 h at room temperature, dehulled; dehulled and soaked; and dehulled, soaked and cooked in distilled water (1:3, w/v), and the effects of removal of polyphenols and phytate on the in vitro protein digestibility (IVPD) and availability of iron and zinc were measured. The results showed that polyphenols and phytate were decreased significantly up to 50.92 and 49.89%, respectively. The IVPD, however, increased up to 38.71 %. The iron and zinc contents decreased up to 18.79 and 18.61%, respectively, but the ionizable iron and zinc were increased up to 55.45 and 80.18%, respectively. This indicated the suitability of simple processing techniques for improvement of availability of nutrients from foxtail millet.

Effect of pectinolytic and amylolytic enzymes on apple juice turbidity

Abstract: The mechanisms governing the enzymatic clarification of apple juice were studied by electron microscopy techniques. Full ripe and unripe apple juice samples (Granny Smith) were treated with commercial pectinase (Solvay 5XLHA) and amylase (Rohalase HT) enzymes, respectively. Scanning electron microscopy studies revealed that commercial amylolytic enzymes quickly reduced starch content in unripe apple juice to undetectable values. It was also observed that after pasteurization of this juice (90C, 5 min) all starch granules gelatinized. Using transmission electron microscopy, it was possible to observe pectin bonded to ripe apple juice particles. This protective colloid is known to be responsible for cloudy juice stability. The effect of pectic enzyme to destroy the protective pectin colloid was also detected with this technique. As a result of the enzymatic treatment, average particle size initially increased from 1000 to 1500 nm and decreased thereafter to ≈1100 nm, and Z-potential increased in absolute values from -9.6 to -11.4 mV. It was speculated that the destruction of the weak pectin net by the action of the specific enzyme caused particle aggregation, followed by the collapse of aggregates, increasing the number of particles <500 nm.

Potassium hydroxide replacement for lye (sodium hydroxide) in tomato peeling

Abstract: Lye (sodium hydroxide [NaOH]) peeling is the most common method for peeling tomatoes in the Midwest U.S. With the rise in the cost of NaOH and the associated disposal problems, alternative methods for peeling need to be examined. Solutions of NaOH, potassium hydoxide (KOH) and calcium hydroxide (Ca[OH] 2 ) at different concentrations were compared to determine their efficacy as peeling agents. Ca(OH) 2 was ineffective as a peeling agent because of its low solubility. KOH produced peeling equivalent to NaOH, but at half the normality. A lower normality is needed because of the increased reactivity of KOH compared to NaOH. This is further demonstrated by the addition of salts to the solution. The use of KOH instead of NaOH may result in cost savings and decreased waste disposal problems.

Functional properties of high hydrostatic pressure‐treated whey protein

Abstract: Surface hydrophobicity, solubility, gelation and emulsifying properties of high hydrostatic pressure (HHP)-treated whey protein were evaluated. HHP treatment of whey protein buffer or salt solutions were performed at 690 MPa and initial ambient temperature for 5, 10, 20 or 30 min. Untreated whey protein was used as a control. The surface hydrophobicity of whey protein in 0.1 M phosphate buffers treated at pH 7.0 increased with an increase in HHP treatment time from 10 to 30 min. HHP treatments of whey protein in salt solutions at pH 7.0 for 5, 10, 20 or 30 min decreased the solubility of whey proteins. A significant correlation was observed between the surface hydrophobicity and solubility of untreated and HHP-treated whey protein with r = −0.946. Hardness of HHP-induced 20, 25 or 30% whey protein gels increased with an increase in HHP treatment time from 5 to 30 min. An increase in the hardness of whey protein gels was observed as whey protein concentration increased. Whey proteins treated in phosphate buffer at pH 5.8 and 690 MPa for 5 min exhibited increased emulsifying activity. Whey proteins treated in phosphate buffer at pH 7.0 and 690 MPa for 10, 20 or 30 min exhibited decreased emulsifying activity. HHP-treated whey proteins in phosphate buffer at pH 5.8 or 7.0 contributed to an increase in emulsion stability of model oil-in-water emulsions. This study demonstrates that HHP treatment of whey protein in phosphate buffer or salt solutions leads to whey protein unfolding observed as increased surface hydrophobicity. Whey proteins treated in phosphate buffers at pH 5.8 and 690 MPa for 5 min may potentially be used to enhance emulsion stability in foods such as salad dressings, sausage and processed cheese.

X-ray assessment of translucency in pineapple

Abstract: A nondestructive method for detection of translucency, a physiological disorder in pineapple, would be beneficial to the industry. Ninety-two pineapples were imaged with X-ray to determine whether translucency could be detected. After imaging, each pineapple was cut open to determine the true level of the disorder and rated on a scale from 1 (no translucency) to 5 (extremely translucent). The X-ray images were inspected by human subjects who evaluated them as either good or bad based on the appearance of translucent and nontranslucent pineapples in training images. The results show a high correlation (R 2 = 0.96) between the likelihood of a sample being rated as good and the actual level of translucency observed. Samples with no translucency were correctly identified 95% of the time, while those with extreme translucency were correctly identified 86% of the time. The results indicate that X-ray imaging is a useful method for selecting either pineapples that are most likely to be free of translucency or those that are most likely to be extremely translucent.

Physicochemical properties of four tomato cultivars grown in nigeria

Abstract: The physicochemical characteristics of tomato fruits from three commercial cultivars available in the local market were compared with a Wild cultivar. The results showed that the Ibadan-Local and Wild cultivars had a higher fruit yield than Ife-1 and Roma-VF cultivars. The Wild cultivar has a high skin and seed content. The shape of the fruits varied from spherical to pear-like. Physicochemical properties such as specific gravity, pH, titratable acidity, ash and refractive index did not vary significantly while total solids, longitudinal (stem→blossom end) and cross-sectional diameters (transverse diameter), vitamin C and reducing sugars were significantly different (P > 0.05) among the cultivars investigated. The results showed that the Wild cultivar has attributes (i.e., physicochemical characteristics) comparable to commercial cultivars to recommend it to breeders for cultivation.

Degradation kinetics of anthocyanin in ethanolic solutions

Abstract: The objective of this study was to investigate the degradation kinetics ofanthocyanininethanolicmodelsolutionssimulatingwineandliqueurinagingor long-term storage. Malvidin-3-glucoside, as the predominant anthocyaninin many cultivars of grape, was chosen to represent anthocyanins. The resultsfrom high performance liquid chromatography analysis show that the disap-pearance of malvidin-3-glucoside follows apparent first-order kinetics, andaccelerates with the increase in ethanol concentration. The E a values werefound to be 22.80, 24.45, 24.35 and 22.75 kcal/mole at 0, 10, 30 and 50%ethanolconcentrations,respectively.Weproposethatthedecreasedstabilityofanthocyanin at an elevated ethanol concentration is a result of a decreasedextent of self-association in the solution. INTRODUCTION Wines and fruit liqueurs that contain anthocyanins are among thecommon alcoholic beverages.Anthocyanins are the major color components inred wine and the color is recognized as an important attribute of wine quality(Romero and Bakker 2000). Many factors affect the stability of anthocyanins,including temperature, pH, the presence of oxygen, enzymes, copigments,metal ions, ascorbic acid, sulfur dioxide, sugars and sugar degradation prod-ucts (Jackman

Ochratoxin a, hydroxymethylfurfural and vitamin c levels of sun-dried grapes and sultanas

Abstract: Ochratoxin A (OTA), hydroxymethylfurfural (HMF) and L-ascorbic acid (vitamin C) levels were detected in sun-dried sultanas and raisins (Vitis vinifera L. cv. Sultanina). Ochratoxins produced by Aspergillus ochraceus, Aspergillus spp., Penicillium viridicatum, Penicillium cyclopium and Rhizophus spp. The main toxin of this group is OTA. It is nephrotoxic and immunotoxic. HMF can occur during nonenzymatic browning reactions that take the form of condensation reactions between amino acids and reducing sugars. It is known as a mutagenic and carcinogenic compound. The sultanas and raisin research samples were sun dried in the field and stored over a long period in the plant. Toxicological quality patterns evaluated for OTA and HMF levels were also evaluated. These are very important compounds for food safety. They are important critical control quality criteria of sun-dried grapes. Vitamin C was examined because of sensitivity against physical and chemical factors such as oxygen, light, thermal treatments, alkali treatment and heavy metals, as well as being important for food labeling. The mean values of OTA in sultanas and raisins were 4.64 and 2.98 μg/kg, respectively. It is determined that the studied samples could be evaluated for safety limit of OTA, which is suggested by the European Community as 10 μg/kg. The HMF values of the samples were 5.50 and 33.57 mg/kg, respectively. The raisins were sun dried. The two types of samples without any pretreatment had a long sun drying period, and they showed higher mean of HMF level with content is had showed higher mean HMF level sultanas. The HMF content is with a critical control point for human health. The mean vitamin C levels of sultanas and raisins were 3.67 and 5.15 mg/100 g, respectively. The mean vitamin C values of sultanas were lower than those of raisins. It was estimated that alkali treatment could cause the destruction of L-ascorbic acid. The vitamin C content of sun-dried grapes does not contribute much to nutrition.

Toasting (dry heat) and nutrient composition, functional properties and antinutritional factors of pigeon pea (cajanus cajan) flour

Abstract: Pigeon pea (Cajanus cajan) beans were separately toasted (dry heat) at 80 and 100C to determine the effects of heat treatment on the nutrients, functional and antinutritional factor contents of the flour. Results showed that the raw sample, 80C treated sample and 100C treated sample had 6.6, 5.18 and 4.48% moisture content, respectively. Ash contents were 5.14, 5.26 and 5.46%; fat contents were 5.40, 5.53 and 6.73%; crude protein contents were 21.32, 21.19 and 20.82%; crude fiber contents were 7.29, 8.02 and 8.01%; and carbohydrate contents were 54.27, 53.82 and 54.52% for raw, 80C treated and 100C treated samples, respectively. Values for functional properties showed that toasting slightly increased water and oil absorption capacities of the flour, while emulsion activities and stability, foam capacities and stability and bulk density were significantly reduced (P < 0.05). Toasting also significantly reduced the antinutritional factors in pigeon flour from 68.0 mg/100 g in raw samples to 23.2 mg/100 g in 100C treated samples in cyanide content, while phytic acid contents were reduced from 120.0 mg/100 g in raw samples to 100.2 mg/100 g in 100C treated samples.

Investigation of protein denaturation and pigment fading in farmed steelhead (onchorhychus mykiss) fillets during frozen storage

Abstract: The present experiment was conducted to measure the extent and nature of quality loss in farmed steelhead fillets during frozen storage, to determine the possible causes of steelhead pigment fading as a result of frozen storage and to suggest some methods for improving storage conditions in order to obtain good-quality frozen steelhead. This two-part study confirms the importance of frozen temperature and appropriate storage conditions on the extension of product shelf life. The fading phenomenon of steelhead fillets during 10 months of frozen storage at -20C was subsequently studied in detail over a 6-week period for fillets stored at both -5 and -30C. Associated protein denaturation, tough/dry texture and rancidity were also examined. Temperature had a stronger effect on the development of rancidity in steelhead fillets than the duration of the storage period for fillets stored for up to 6 weeks. Highest levels of oxidation products were observed in the fillets stored at -5C even in the short-term storage experiment while extensive lipid oxidation, toughening, expressible fluid loss on thawed fillets and apparent pigment fading took place during long-term storage at -20C. The results from sensory evaluation of texture, color and flavor agreed well with the chemical assessment of rancidity. Flavor scores from the fillets stored at -5C revealed a slightly oily/rancid taste as compared to the samples at -30C after 6 weeks of storage. The expressible fluid results indicated that the binding of water to protein decreased significantly in fillets stored at -5C as compared to the matching fillets at -30C and during long-term storage at -20C. The increases in expressible fluid correlated positively with fading (L*) and negatively with redness (a*). The quantity of extractable protein nitrogen (EPN) decreased drastically over the 6-week period in both temperature groups (-5 and -30C), but during this relatively short experiment, the EPN levels between temperature treatments were not significantly different. In both experiments, fillet redness faded dramatically as a result of frozen storage. Abusive cold storage at -5C resulted in far more fading than at -30C even after 6 weeks. Fading was measured both subjectively and objectively using reflectance colorimetry, and an increase in whiteness value was concomitant with a decrease in redness. It is suggested that whiteness may be used as an accurate subjective parameter for color fading in frozen storage. Redness values were significantly higher in the fillets at -30C. The study showed that pigment fading was not a result of a decrease in carotenoid concentration but may be related to protein denaturation, which causes muscle tissue appearance to change from translucent to opaque, thereby giving the illusion of pigment fading.

Flavor and aroma attributes of riesling wines produced by freeze concentration and microwave vacuum dehydration

Abstract: This article describes the production of sweet dessert wines produced using late-harvest freeze concentration, wine produced from fresh grapes frozen using refrigeration and wine produced from grapes partially dried using microwave vacuum dehydration. The objective was to compare the aroma and flavor attributes of the wines to determine the effect of each method of juice concentration. The replicated wine samples were evaluated by 12 experienced judges, and the wines were analyzed using solid-phase microextraction. The microextraction detected 28 compounds; however, levels of concentration of these compounds were below published aroma thresholds. Although all the wines were judged as acceptable sweet dessert wines, the judges detected significant differences. The wine made from the dehydrated grapes exhibited lower fresh fruit aroma, higher fusel oils and oxidation, and flavor notes including citrus/grapefruit and acidity were lower.

Radio frequency-hot water dips for postharvest codling moth control in apples

Abstract: A combination radio frequency-hot water dip method was examined as a potential quarantine treatment against fifth instars of the codling moth, Cydia pomonella L. (Lepidoptera: Tortricidae), in apples, Malus sylvestris (L.) var. domestica (Borkh.) Mansf., which were intended for export to Japan. The apples were initially exposed to 27.12-MHz radio frequency energy at 12 kW for 2.75 min and were then submerged in a range of hot water dips (48‐50C) for different durations. Efficacious tests were at 48C for >2 h, at 49C for >50 min and at 50C for >40 min. Fruit quality tests indicated that the best hot water parameters were at 50C for 40 min. Fruit quality after 2 weeks was cultivar dependent where “Fuji” apples tolerated heat treatment better than “Delicious” and “Gala” apples. None of the treated fruits were acceptable after 60 days. Regardless of cultivar, heat treatment resulted in loss of both peel and fresh colors, coupled with reduced firmness and increased external and internal damage.

Mortality and quality indices of live west african hard-shell clams (galatea paradoxa born) during wet and dry postharvest storage

Abstract: Freshly harvested clams (Galatea paradoxa Born) obtained from the Cross River, Nigeria were subjected to live storage for 7 days in or outside of water. The objective was to study the effects of storage method and duration on mortality, weight changes and selected physical and physicochemical properties of the clams. Overall, 62 or 35% of the stored clams died over the 7-day duration under wet (potable water) or dry storage, respectively. No deaths were recorded in day 1 (wet storage) or in days 1-3 (dry storage). Regression analysis showed linear relationships between storage duration and each of the dependent-quality variables of weight change, density, pH and electrical conductivity (EC) evaluated under both storage methods. The regression coefficients (pl, β2) for assayed quality parameters in wet or dry storage were significantly different (P ≤ 0.05). R 2 were generally larger for dry storage than for wet storage. Initial clam weights did not significantly (P ≥ 0.05) affect weight change during storage, indicating that weight loss during dry storage was statistically invariant with clam weight. The study concludes that priority should be given to prompt sale and utilization (<3 days) of clams, particularly large clams. The use of dry storage to reduce postharvest mortality and weight losses will potentially increase the profitability of the clam industry.

Development of a high‐moisture shelf‐stable grated carrot product using hurdle technology

Abstract: Carrot (Daucus carota) can be highly perishable and difficult to preserve fresh for long periods at ambient temperature and humidity. Studies on grated carrots were carried out for the development of a shelf-stable moist-preservation process based on infusion of additives using hurdle technology. Additives comprising 3.0% sodium chloride (to reduce water activity [A w ] to 0.94), 0.9% citric acid (to reduce pH to below 4.5), 1.0% sodium citrate and 0.2% sodium benzoate (as antimicrobial agents) were followed by partial dehydration. The product was stored in flexible polymeric pouches. The physical, chemical and pathological stability was monitored during storage at ambient temperatures (19-33C). The partially dehydrated grated carrots (moisture 66.2%) were acceptable for more than six months at ambient temperature with the retention of carotenoid up to 82.5%. The product was microbiologically safe throughout the study.

Pressure conditions and quality of chicken nuggets fried under gaseous nitrogen atmosphere

Abstract: The potential for using nitrogen gas as a pressurizing medium in a deep-fat fryer was investigated. Effects of different frying temperatures (150, 175 and 190C) and pressures (101, 163 and 184 kPa) on the fried food quality were studied. Chicken nuggets were either fried for a constant frying time of 240 s or at a constant core temperature of 70C in a modified restaurant-type pressure fryer. Modifications were made to include external gases to pressurize the frying chamber. The quality characteristics of the fried products were determined. An increase in pressure applied during frying resulted in tender and juicier fried products because of the reduction in moisture loss. The increase in pressure reduced oil uptake by the fried products. Compared with the use of steam released from the food, frying under nitrogen gas provided similar or better quality of fried products in terms of moisture retention, juiciness and texture.