Natural Orange Juice Research Articles

Eficácia de atrativos alimentares na captura de moscas-das-frutas em pomar de citros

As moscas-das-frutas (Diptera: Tephritoidea) são importantes pragas de frutas cítricas no Estado de São Paulo, principalmente Anastrepha fraterculus (Wied.) e Ceratitis capitata (Wied.). O objetivo deste estudo foi medir a eficiência dos atrativos alimentares para monitoramento de moscas-das-frutas, em pomar de citros. O delineamento experimental adotado foi de blocos ao acaso com cinco tratamentos e cinco repetições. O ensaio foi instalado em 30/9/2003 e desenvolvidopor nove semanas. Os atrativos testados foram: proteínas hidrolisadas comerciais Bio Anastrepha, Isca Mosca e Aumax®, todas diluídas em água a 5%; melaço a 7% isoladamente e melaço a 7% em mistura com suco de laranja a 10%. Foram utilizados semanalmente, 400mL da solução atrativa por frasco plástico McPhail instalado na copa de laranjeiras da variedade 'Pêra Rio'. As soluções eram renovadas semanalmente, ocasião em que os adultos eram coletados e çevados ao laboratório para contagem, sexagem e identificação. Foram capturados 1.821 adultos de Tephritoidea, sendo 892 de Anastrepha spp., 731 de C. capitata e 198 de Neosilba spp. Para essas espécies, as proteínas Bio Anastrepha e Isca Mosca foram altamente eficientes e semelhantes entre si, capturando 44,5% e 41,3% dos adultos de Tephritidae respectivamente. Não houve diferença entre as espécies de Tephritidae analisadas por sexo capturadas em Bio Anastrepha, Aumax® e melaço. Aumax®, melaço isoladamente e melaço + suco de laranja atraíram apenas 4,6%, 1,3% e 1,2% do total de adultos de Tephritidae, respectivamente. Melaço isoladamente e melaço com suco de laranja foram mais eficazes na atratividade de Zaprionus indianus (Gupta) (Diptera: Drosophilidae).

Control of Alicyclobacillus acidoterrestris in fruit juices by enterocin AS-48

Alicyclobacillus acidoterrestris is a spoilage-causing bacterium in fruit juices. Control of this bacterium by enterocin AS-48 from Enterococcus faecalis A-48-32 is described. Enterocin AS-48 was active against one A. acidocaldarius and three strains of A. acidoterrestris tested. In natural orange and apple juices incubated at 37 °C, vegetative cells of A. acidoterrestris DSMZ 2498 were inactivated by enterocin AS-48 (2.5 μg/ml) and no growth was observed in 14 days. In commercial fruit juices added of AS-48 (2.5 μg/ml) and inoculated with vegetative cells or with endospores of strain DSMZ 2498, no viable cells were detected during 90 days of incubation at temperatures of 37 °C, 15 °C or 4 °C, except for apple, peach and grapefruit juices inoculated with vegetative cells and incubated at 37 °C which were protected efficiently for up to 60 days. Remarkably, in all commercial fruit juices tested, no viable cells were detected as early as 15 min after incubation with the bacteriocin. Endospores incubated for a very short time (1 min) with increasing bacteriocin concentrations were inactivated by 2.5 μg/ml AS-48. Electron microscopy examination of vegetative cells and endospores treated with enterocin AS-48 revealed substantial cell damage and bacterial lysis as well as disorganization of endospore structure.

DYNAMIC ANALYSIS of the COOLING PROCESS IN PLATE HEAT EXCHANGERS

ABSTRACTThis paper describes a dynamic simulation of a mathematical model that describes the cooling process of natural orange juice in plate heat exchangers. the goal was to obtain an evaluation of the process reaction curves, represented by the behavior of the outlet orange juice's temperature after simultaneous disturbances to the following process variables: product and refrigerant fluid temperatures and mass flow rates. the simulator was encoded using the Mat‐Lab program, whose effectiveness had been previously validated (predicted values were within 2% of the published values). Assays were simulated based on the factorial design technique. the importance of variable interaction was evaluated and it was shown that each combination of disturbances to the process gave way to different effects on outlet temperature stabilization values and on the behavior of process reaction curves. the monitoring of the process variable transient behavior has been found to aid in tuning controllers throughout this process, which requires, according to the results, nonconventional coutrollers for truly efficient automation.

Changes in quality of natural orange juice pasteurised by high pressure during storage

Natural orange juice pasteurised (pascalised) by high pressure was stored for 180 days at room temperature in dark conditions. Sensory evaluation of several quality parameters was made. At the same time the frozen and heat pasteurised parallel samples of the juice of the same origin were evaluated for comparison. The sensory evaluation consists of overall image, flavour, taste and sensorial viscosity. The instrumental evaluation of colour, pH and kinematic viscosity was made. The best overall image was received for frozen juice. The pressurised and heated samples were nearly the same as regards the flavour. The sensorial viscosity of all samples was evaluated as thin with very small differences during storage. The preference test was also made – the best quality for the test panel was received for samples of frozen juice followed by pressurised juice. The third rank was given to heat treated samples. The pressurised samples exhibited the acceptable quality for 150 days of storage at room temperature.

Use of pectinesterase for detection of hydrocolloids addition in natural orange juice

In natural orange juice, pectin is the major constituent responsible for cloud stability. In adulterated and imitation orange juices, for technical reasons, cloud stability is effected by different natural or synthetic hydrocolloids. Pectinesterase, an enzyme specific for pectin hydrolysis, was used to detect substitution of natural pectin of orange juice by other hydrocolloids. Natural orange juice, imitation orange juice and mixtures of them were used in this study. In pasteurized orange juice samples, pectinesterase was added at 20 mg/100 ml of juice. Mixtures were heated at 50°C in a water bath for 24 h and the percentage of clarification, as well as the amount of precipitate formed after centrifugation were measured. A linear correlation was found to exist between natural orange juice percentage in the natural–imitation orange juice mixtures and precipitate formed. A second order relation was found to exist between the percentage of the natural orange juice in the natural–imitation orange juice mixtures and the degree of clarification of orange juice. The method was used successfully for the detection of addition of extraneous hydrocolloids in orange juice for adulteration purposes.

Involvement of proteins in cloud instability of shamouti orange [Citrus sinensis (L.) Osbeck] juice.

The present study provides evidence for the involvement of protein in cloud instability of natural orange juice. No heat-coagulable proteins were found in the serum. Insoluble cloud matter (ICM) was heat-flocculated following enzymatic pectin degradation (EPD). The degree of flocculation depended on temperature (from approximately 50 to 75 degrees C) and was highest at pH 3.5. The fresh juice contained about 6.5 and 1.8 mg mL(-1) of ICM and alcohol-insoluble solids of the serum (AISS), respectively. The ICM and the AISS contained, respectively, proteins (182+/-14 and 119+/-3 microg mg(-1)), galacturonic acid (37+/-6.6 and 175+/-1 microg mg(-1)), and neutral sugars (350+/-44 and 338+/-22 microg mg(-1)). EPD resulted in removal of a marked portion of the pectin and was accompanied by partial removal of neutral sugars (mainly glucose and galactose) and some proteins from the pectic polymer in both AISS and ICM. Under electrophoresis, proteins of the AISS included bands in the range of 20-52 kDa and 10-14 kDa and those of the ICM at 22 and 50 kDa.

Automatic potentiometric titration in monosegmented flow system exploiting binary search

An automatic monosegmented flow system (MSFA) based on the binary search concept to perform potentiometric titration is proposed. A tubular hydrogen ion-selective electrode without inner reference solution, consisting of a conducting epoxy cylinder machined with an axial hole coated with tridodecylamine (TDDA) was employed as a sensor. The titration procedure was implemented by exploiting the binary search approach, after each analytical cycle data were evaluated to decide the variation of the titrant volumetric fraction to be inserted for the next cycle. The flow network comprised three-way solenoid valves controlled by a microcomputer running software in QUICKBASIC 4.5. Combination of binary search and MSFA resulted in an automatic system providing possibilities to perform flow titrations without any operator assistance. The main features of the proposed system were verified by titrating hydrochloric and acetic acid solutions and the feasibility of the approach was ascertained by analyzing vinegar, coke, lemon soda, isotonic, industrial and natural orange juice samples. Results were in agreement with those obtained with a conventional potentiometric titration, and no significant difference at 95% confidence level was observed. A 1% standard deviation ( n=9) in results was also observed.

A novel method for the determination of vitamin C in natural orange juices by electrochemical monitoring of dediazoniation of 3-methylbenzenediazonium tetrafluoroborate

A novel procedure for the determination of L-ascorbic acid (vitamin C, AA) in natural orange juice samples is described. First, we examine the kinetics of reactions of m-methylbenzenediazonium ( mMBD) tetrafluoroborate in aqueous solutions. The method involves two electrochemical procedures: by directly monitoring diazonium salt loss (dediazoniation reaction) and by monitoring the derivatization product from coupling unreacted diazonium ions with 2-naphthol-6-sulphonic acid to give an azo dye (coupling reaction). The diazonium ions, dediazoniation products and derivatization products like azo dyes are electroactive compounds, showing well-defined peaks at −50 and −430 mV for diazonium ions, at +1.236 V for m-cresol (major dediazoniation product), both in 0.1 M HCl, and −659 mV for the azo dye in 0.01 M NaOH (all peak potentials vs. Ag/AgCl reference electrode). Secondly, a differential pulse polarographic method based on the accelerating effect of AA on the dediazoniation reaction of mMBD is described. This reaction is strongly accelerated in the presence of AA. The observed rate constant is linearly correlated with the total AA concentration and the calibration graph is linear over at least three orders of magnitude. mMBD kinetics are first-order (with respect to mMBD) in absence of and in presence of AA.

Radiação gama na conservação do suco natural de laranja

Este trabalho estudou o efeito da radiação gama na população microbiológica, teor de sólidos solúveis, acidez titulável, pH and conteúdo de vitamina C do suco natural de laranja. A atividade microbiana pode causar a deterioração do suco de laranja. A irradiação é um processo de conservação de alimentos através da eliminação dos microrganismos, porém pode afetar algumas características do produto. O delineamento experimental foi em esquema fatorial 4x5 referentes ao controle mais 3 doses de radiação (2,0; 4,0 and 6.0 kGy) e 5 períodos de armazenamento (1, 7, 14, 21 e 28 dias) com 2 repetições. As amostras de suco natural foram extraídas de laranjas da variedade "Pêra", irradiadas a uma taxa de dose de 2,0 kGy por hora (cobalto-60), e em seguida foram armazenadas sob refrigeração (5 ± 3ºC). Os resultados mostraram pequenas variações no teor de sólidos solúveis, acidez titulável e pH, em relação aos tratamentos testados. A razão sólidos solúveis/acidez titulável foi determinada e também mostrou pequena variação em todos os tratamentos. Com o aumento da dose de radiação e o prolongamento do período de armazenamento houve redução no conteúdo de vitamina C do suco. A radiação gama se mostrou eficaz na redução da população microbiana do suco de laranja.

DEVELOPMENT OF A PROTEIN FORTIFIED FRUIT BEVERAGE AND ITS QUALITY WHEN PROCESSED WITH PULSED ELECTRIC FIELD TREATMENT

ABSTRACTPulsed electric field treatment (PEF), was explored to process a beverage at 30C. A protein fortified fruit based beverage was developed using proteins, orange juice, guar gum, sucrose, calcium lactate, citric acid, natural flavor and color. It was processed at low pH (3.75) using both a heat pasteurization and a PEF treatment. PEF treated beverage had less protein denaturation and lower loss of vitamin C compared with that of the heat treated beverage. The heat treated beverage had a slightly higher apparent viscosity than the PEF treated beverage and developed sedimentation in the container during storage. The PEF processed beverage maintained its natural orange juice like color better than the heat treated beverage, which developed a slightly whitish color. However, the PEF treated product was less microbiologically stable (5 months) at refrigeration temperature compared with the heat treated product which was stable for more than 12 months. It was concluded that more technological improvements are needed to process food safely by PEF technology.

Ascorbic Acid Determination in Natural Orange Juice: As a Teaching Tool of Coulometry and Polarography

Procedure for determining the concentration of ascorbic acid in orange juice using electroanalytical techniques (coulometry and polarography).

Removal of ascorbic acid interference in the determination of glucose and sucrose in non-alcoholic beverages

A flow-injection system with an immobilized-enzyme, single-bead string reactor has been used to study the ascorbic acid interference in the determination of glucose and sucrose. Glucose was enzymatically determined in standard solutions and in samples of non-alcoholic beverages. After the measurement of glucose, the samples were spiked with different amounts of ascorbic acid, which was found to introduce serious errors even in low concentrations. A procedure for treating the samples containing ascorbic acid with ascorbase is proposed. The treatment completely removes the interference effect and ensures the recovery of the true concentration of glucose present in the measured samples. The method was applied to determinations of glucose and sucrose in soft drinks and in natural orange juice. The relative standard deviation of the procedure is ±3%.

The effects of ascorbic acid and flavonoids on the occurrence of symptoms normally associated with the common cold

A controlled study was made of the effects of natural orange juice, synthetic orange juice, and placebo in the prevention of the common cold; both natural and synthetic orange juices contained 80 mg of ascorbic acid daily. Three-hundred sixty-two healthy normal young adult volunteers, ages 17 to 25 years, were studied for 72 days with 97% of participants completing the trial. There was a 14 to 21% reduction in total symptoms due to the common cold in the supplemented groups that was statistically significant (P < 0.05). Ascorbic acid supplementation also increased the number of “episode-free” subjects. However, the clinical usefulness of the results does not support prophylactic ascorbic acid supplements in the well-nourished adult. The results in this study with both natural and synthetic orange juice of physiological content of ascorbic acid, are similar to those obtained using a “megadose” of ascorbic acid.

Effect of some citrus juice constituents on taste thresholds for limonin and naringin bitterness

AbstractA panel of 20 to 27 screened judges was used to determine the threshold of pure limonin and naringin in distilled water, sucrose solutions, citric acid solutions adjusted to various pH values and in citrus juice model systems. Thresholds in distilled water were 1 and 20 mg/l for limonin and naringin, respectively. Sucrose, citric acid and combinations of these constituents in a model system increased the threshold of limonin and naringin several fold. The highest thresholds were obtained at low pH values in the absence of sugar. In a 1.2% citric acid solution containing 5% sucrose, 2.5% dextrose and 2.5% fructose the maximum limonin threshold of 11 mg/kg was obtained at pH 3.8. The maximum difference threshold for limonin in orange juice was 6.5 mg/kg and also occurred at pH 3.8. The optimum pH for limonin bitterness suppression (maximum threshold) was 3.8 in both model systems and natural orange juice. Thresholds on either side of this value were lower and limonin bitterness was more noticeable. No pH optimum was observed for naringin threshold in model systems. Individual thresholds showed a wide range of sensitivity to both limonin and naringin bitterness.