A fully integrated 3D printed platform for sulfite determination in beverages via gas diffusion membrane extraction and digital video treatment.

In this study, we have described a miniaturized, simple, and low-cost device for sulfite determination in beverages by coupling Gas Diffusion Microextraction to paper-based analytical devices. The color change of an acid-base indicator - promoted by the generated gaseous SO2 - impregnated onto the paper surface was monitored in the function of time by video recording using a smartphone. The analytical information was related to the Hue, Saturation, Value (HSV) color space extracted from the video file. The complete analytical platform was built using a 3D printer, allowing the easy fabrication of a low-cost tailored device. Under optimized conditions, a linear relation from 5 to 90 mg L-1 was obtained using 30 µL of the reagent, 1 mL of sample, and 10 min of analysis. The relative standard deviation and the limit of detection were 2.2 % and 1.6 mg L-1, respectively. The method was successfully employed in several beverages, such as juices, soda, and coconut water.

Reagent-less and sub-minute quantification of sulfite in food samples using substrate-integrated hollow waveguide gas sensors coupled to deep-UV LED.

The increasing consumption of processed foods demands the usage of chemical preservatives to ensure freshness and extended shelf life. For this purpose, sodium sulfite and its derivatives have been widely used in a variety of food products to inhibit microbial spoilage and for mitigating oxidative decay. However, the excessive consumption of sulfite may cause health problems, thus requiring rapid and accurate analytical methods for the rapid identification of threshold levels. Conventionally, sulfite is volatilized from food samples by acidification followed by trapping of the gaseous SO2 and determination using a suitable analytical technique. Herein, we propose a yet unprecedented reagent-less approach via direct absorbance measurements of gaseous SO2 at 280 nm after sample acidification. The detection system combines a deep-UV LED and a SiC photodiode with a substrate-integrated hollow waveguide (iHWG) gas cell. Absorbance measurements were performed using a log-ratio amplifier circuitry, resulting in noise levels <0.7 mAU. This innovative concept enabled the determination of sulfite in beverages in the range of 25-1000 mg L-1 with suitable linearity (r2 > 0.99) and an analysis time <30 s. The limit of detection (LOD) was calculated at 14.3 mg L-1 (3σ) with an iHWG providing an optical path length of 75 mm. As a proof of concept, this innovative analytical platform was employed for sulfite quantification in concentrated grape juice, coconut water and beer, with suitable accuracy in terms of recovery (83-117%) and favorable comparison with the official Monier-Williams method. Given the inherent modularity and adaptability of the device concept, we anticipate the application of the proposed analytical platform for the in-situ studies addressing sulfite and other volatilized preservatives in a wide variety of food products with tailorable detectability.

Rapid method for the determination of citrate, phosphate and sulfite in seafood by capillary zone electrophoresis.

Since seafood is susceptible to decomposition, additives may be used to maintain its quality. However, some additives may be improperly used to disguise spoilage, thus resulting in food fraud. Market growth demands faster and more reliable quality control tools that incorporate the most common additives in a single analysis. This study developed a rapid analytical method for the determination of citrate, phosphate and sulfite in seafood by capillary zone electrophoresis with indirect UV-Vis detection. Electrophoretic separation was achieved in less than 3.5 min. The background electrolyte consisted of 20 mmol L-1 of benzenesulfonic acid and 45 mmol L-1 of aminocaproic acid. After validation, the method was applied for 24 seafood real samples. Citrate was found in five samples. Four samples presented higher phosphate and sulfite concentrations than those permitted by Brazilian legislation. Good analytical performance indicates that the method is a viable alternative for food control in routine analysis.

In-line electrochemical reagent generation coupled to a flow injection biamperometric system for the determination of sulfite in beverage samples.

This work reports an in-line electrochemical reagent generation coupled to a flow injection biamperometric procedure for the determination of SO3(2-). The method was based on a redox reaction between the I3(-) and SO3(2-) ions, after the diffusion of SO2 through a gas diffusion chamber. Under optimum experimental conditions, a linear response ranging from 1.0 to 12.0 mg L(-1) (R=0.9999 and n=7), a detection and quantification limit estimated at 0.26 and 0.86 mg L(-1), respectively, a standard deviation relative of 0.4% (n=10) for a reference solution of 4.0 mg L(-1) SO3(2-) and sampling throughput for 40 determinations per hour were achieved. Addition and recovery tests with juice and wine samples were performed resulting in a range between 92% and 110%. There were no significant differences at a 95% confidence level in the analysis of eight samples when comparing the new method with a reference procedure.

Extraction and quantification of SO2 content in wines using a hollow fiber contactor.

Sulfites [Formula: see text] or sulfur dioxide (SO2) is a preservative widely used in fruits and fruit-derived products. This study aims to propose a membrane contactor process for the selective removal and recovery of SO2 from wines in order to obtain its reliable quantification. Currently, the aspiration and Ripper methods offer a difficult quantification of the sulfite content in red wines because they involve evaporation steps of diluted compounds and a colorimetric assay, respectively. Therefore, an inexpensive and accurate methodology is not currently available for continuous monitoring of SO2 in the liquids food industry. Red wine initially acidified at pH < 1 was treated by membrane extraction at 25 ℃. This operation is based on a hydrophobic Hollow Fiber Contactor, which separates the acidified red wine in the shell side and a diluted aqueous sodium hydroxide solution as receiving solution into the lumenside in countercurrent. Sulfite and bisulfite in the acidified red wine become molecular SO2, which is evaporated through the membrane pores filled with gas. Thus, SO2 is trapped in a colorless solution and the membrane contactor controls its transfer, decreasing experimental error induced in classical methods. Experimental results using model solutions with known concentration values of [Formula: see text] show an average extraction percentage of 98.91 after 4 min. On the other hand, two types of Chilean Cabernet Sauvignon wines were analyzed with the same system to quantify the content of free and total sulfites. Results show a good agreement between these methods and the proposed technique, which shows a lower experimental variability.

Análises de sulfitos em alimentos: o método padrão monier-williams é a melhor alternativa? / Analysis of sulfites in foods: the method Monier-Williams is the best alternative?

Os sulfitos fazem parte deum importante grupo deaditivos, utilizados comoconservantes em frutassecas, sucos de frutas, vinhos e emvários outros alimentos, como cogumelos(champignon) e pescados,há séculos. Quando na forma ativadióxido de enxofre (S02), atuamcomo conservantes, biocidas, anti-oxidantes e inibidores de enzimasque provocam o escurecimento enzimáticodos alimentos (KELLY et al.2002;JARVIS & LEA, 2000). Apesarde vários estudos (LECLERCQ et al.2000; LARSEN & PASCAL, 1998;RENWICK, 1996) demonstraremque, quase sempre, são os consumidoresde grandes quantidades dosalimentos contendo este aditivo,aqueles mais expostos ao risco de alcançarem ou ultrapassarem a ingestãodiária aceitável (IDA). Porém,ainda há necessidade de monitoramentoperiódico das quantidades deaditivos utilizados pelas indústrias dealimentos e as quantidades realmenteconsumidas pela população. (AU)

Critical comparison between modified Monier-Williams and electrochemical methods to determine sulfite in aqueous solutions.

In the present work, known concentration of sulfite aqueous solutions in the presence and absence of gallic acid was measured to corroborate the validity of modified Monier-Williams method. Free and bound-sulfite was estimated by differential pulse voltammetry. To our surprise, the modified Monier-Williams method (also known as aspiration method) showed to be very inaccurate for free-sulfite, although suitable for bound-sulfite determination. The differential pulse approach, using the standard addition method and a correction coefficient, proved to be swift, cheap, and very precise and accurate.

Indirect determination of sulfite using a polyphenol oxidase biosensor based on a glassy carbon electrode modified with multi-walled carbon nanotubes and gold nanoparticles within a poly(allylamine hydrochloride) film.

The modification of a glassy carbon electrode with multi-walled carbon nanotubes and gold nanoparticles within a poly(allylamine hydrochloride) film for the development of a biosensor is proposed. This approach provides an efficient method used to immobilize polyphenol oxidase (PPO) obtained from the crude extract of sweet potato (Ipomoea batatas (L.) Lam.). The principle of the analytical method is based on the inhibitory effect of sulfite on the activity of PPO, in the reduction reaction of o-quinone to catechol and/or the reaction of o-quinone with sulfite. Under the optimum experimental conditions using the differential pulse voltammetry technique, the analytical curve obtained was linear in the concentration of sulfite in the range from 0.5 to 22 µmol L(-1) with a detection limit of 0.4 µmol L(-1). The biosensor was applied for the determination of sulfite in white and red wine samples with results in close agreement with those results obtained using a reference iodometric method (at a 95% confidence level).

Environmental mutagenicity and toxicity caused by sodium metabisulfite in sea shrimp harvesting in Piauí, Brazil.

Sodium metabisulfite is used in marine shrimp harvesting to prevent the occurrence of black spots. Shrimps are soaked in a sodium metabisulfite solution in ice, which is disposed of in sewages that run into marine canals, creating an environmental hazard. This study evaluates the toxicity and mutagenicity caused by sodium metabisulfite in sea waters and sediments collected in a shrimp farm in Cajueiro da Praia (Luis Correia), state of Piauí, Brazil, using the Allium cepa assay. Water and sediment samples were collected in the dry and in the rainy seasons, in three sites: upstream the shrimp farm (Site 1), at the point sodium metabisulfite is discharged (Site 2), and 100 m downstream the farm (Site 3). Three sample dilutions were used (50%, 25% and 10%) for all samples. A negative control (well water) and a positive control (copper sulfate 0.0006 mg mL⁻¹) were used in each experiment. At the end of the 72-h exposure period, onion roots were measured and removed. Mutagenicity analysis included the determination of mitotic index, chromosomal aberrations and the detection of micronuclei; analysis of root size and mitotic index were used as an index of toxicity. The A. cepa assay revealed that the water and sediments samples collected in the Piauí coast contaminated with sodium metabisulfite induce toxicity. The results demonstrate that the assay may be used as a regular tool in the analysis of water parameters in shrimp farms in the coast of Piauí state, and in strategies to preserve the region's marine ecosystem.

Análise de sulfitos em sucos de frutas e estimativa de seu consumo por escolares / Analytical determination of sulphites in fruit juices and estimation of their intake by students

No Brasil os dados sobre a utilização dos sulfitos pela indústria de alimentos e pesquisas sobre o seu consumo são escassos. Sendo assim, o objetivo desta pesquisa foi avaliar o nível de sulfitos em sucos de frutas e estimar seu consumo por escolares de 5ª. a 8ª. séries de escolas públicas, do ensino fundamental, do município de São Caetano do Sul-SP, Brasil. Foi aplicado questionário de freqüência de consumo de alimentos (QFCA) em 313 escolares, sendo 56,9 % do sexo feminino e 43,1 % do sexo masculino, com média de idade de 14,7 anos. Os alimentos sulfitados mais consumidos foram os néctares ou sucos de frutas, o açúcar refinado, as batatas fritas congeladas, o coco ralado, o suco de caju e as frutas secas e cristalizadas. Considerando os limites máximos permitidos (LMP) pela legislação brasileira, o consumo de SO2, em mg SO2/kg pc/dia, foi de 0,12 mg SO2/kg pc/dia, sendo que este valor médio corresponde a 17% da IDA (0,7 mg SO2/kg pc/dia). Já os resultados das análises dos sucos de frutas demonstram que a análise por injeção em fluxo (Flow injection analysis - FIA) modificada obteve resultados de sulfitos nas amostras analisadas com menor variação do que aqueles obtidos pelo método Monier-Williams (M-W) otimizado, e que nenhuma amostra ultrapassou os LMP.

In Brazil there are no data on use of sulphites by the food industry and research on their consumption by population. Thus, the objective of this research was to evaluate sulphites in fruits juices and estimate intake sulphites in a group of 5th 8th schoolchildren of public schools in São Caetano do Sul-SP, Brazil. It was applied a food frequency questionnaire (FFQ) at 313 schoolchildrens (56.9% female, 43.1% male and average age 14.7 years). Sulphited products identified were fruits juices, sugar, frozen chips, grated coconut, cashew juice and dried fruits. Considering maximum permitted levels (MPL) stabilished by Brazilian legislation, none of the students exceeded the ADI of 0.70 mg SO2/kg bw/day, with average of consumption of 0.12 mg SO2/kg bw/day (17 % of the ADI). The results of the fruits juices analysis demonstrated flow injection analysis (FIA) modified obtained better results than optimized Monier-Williams method (M-W) and no sample exceeded the MPL.

Presença de aditivos conservantes (nitrito e sulfito) em carnes bovinas moídas, comercializadas em mercados varejistas / Presence of additive conserving (nitrite and sulphite) in grounded beef, commercialized in the retail markets

No presente trabalho, objetivou-se avaliar a prática fraudulenta da adição de nitrito e sulfito, e parâmetros físico-químicos de qualidade em carnes bovinas moídas in natura e resfriadas, comercializadas em mercados varejistas do estado do Rio de Janeiro. Avaliou-se também o grau de depleção do nitrito pós-cocção. Os resultados obtidos demonstraram que de 35 amostras analisadas, 37,14% apresentaram nitrito, 11,42% sulfito, 17,14% amônia e 17,14% odor desagradável na prova da cocção. Todas as amostras apresentaram o valor de pH dentro do padrão oficial. A maior concentração de nitrito detectada foi 1,17mg.Kg-1 e a menor 0,173 mg.Kg-1. Após cozimento de amostras onde se detectou nitrito, houve depleção significativa desta substância. A detecção de nitrito e sulfito em carnes in natura além de caracterizar o descumprimento da legislação vigente por parte dos comerciantes, pode representar um risco à saúde da população, devido ao potencial tóxico destas substâncias quando ingeridas em excesso.(AU)

So, the present work aims to evaluate the quality physiochemical parameters as well as the nitrite and sulphite fraudulent addition to “in natura” grounded beef which was cooled commercialized in the State of Rio retail markets. The nitrite depletion degree after cooking was also evaluated. Our results have demonstrated that in 35 analyzed samples, 37.14% presented sodium nitrite while 11.42% sulphite, 17.14% ammonia and 17.14% unpleasant smell at cooking test. All the samples presented standard pH value. 1.17 mg.Kg-1 and 0.173 mg.Kg-1 were the highest and the lowest nitrite concentration detected, respectively. We found significant depletion of the nitrite after cookihg the samples with this substance. The detention of nitrite and sulfite in meats “in natura” characterizes the disobedience of the current law. The addition of these substances can represent a risk to the health of the population. They are potentially toxic substances when ingested in excess.(AU)

Presença de aditivos conservantes (nitrito e sulfito) em carnes bovinas moídas, comercializadas em mercados varejistas / Presence of additive conserving (nitrite and sulphite) in grounded beef, commercialized in the retail markets

No presente trabalho, objetivou-se avaliar a prática fraudulenta da adição de nitrito e sulfito, e parâmetros físico-químicos de qualidade em carnes bovinas moídas in natura e resfriadas, comercializadas em mercados varejistas do estado do Rio de Janeiro. Avaliou-se também o grau de depleção do nitrito pós-cocção. Os resultados obtidos demonstraram que de 35 amostras analisadas, 37,14% apresentaram nitrito, 11,42% sulfito, 17,14% amônia e 17,14% odor desagradável na prova da cocção. Todas as amostras apresentaram o valor de pH dentro do padrão oficial. A maior concentração de nitrito detectada foi 1,17mg.Kg-1 e a menor 0,173 mg.Kg-1. Após cozimento de amostras onde se detectou nitrito, houve depleção significativa desta substância. A detecção de nitrito e sulfito em carnes in natura além de caracterizar o descumprimento da legislação vigente por parte dos comerciantes, pode representar um risco à saúde da população, devido ao potencial tóxico destas substâncias quando ingeridas em excesso.

So, the present work aims to evaluate the quality physiochemical parameters as well as the nitrite and sulphite fraudulent addition to “in natura” grounded beef which was cooled commercialized in the State of Rio retail markets. The nitrite depletion degree after cooking was also evaluated. Our results have demonstrated that in 35 analyzed samples, 37.14% presented sodium nitrite while 11.42% sulphite, 17.14% ammonia and 17.14% unpleasant smell at cooking test. All the samples presented standard pH value. 1.17 mg.Kg-1 and 0.173 mg.Kg-1 were the highest and the lowest nitrite concentration detected, respectively. We found significant depletion of the nitrite after cookihg the samples with this substance. The detention of nitrite and sulfite in meats “in natura” characterizes the disobedience of the current law. The addition of these substances can represent a risk to the health of the population. They are potentially toxic substances when ingested in excess.

Evaluation of the formation and stability of hydroxyalkylsulfonic acids in wines.

The presence of carbonyl compounds (CCs) in wines has sparked the interest of researchers in several countries. The quantification of some of these compounds has been used as a parameter of quality for many fermented beverages. Although present in minute quantities (except for acetaldehyde), they have a strong olfactory impact. In addition, the CCs found in wines have a strong affinity for bisulfite and can form stable adducts, which will also interfere in the characteristics of aroma. The greatest challenge, however, is to predict which CCs have the strongest affinity for S(IV) and what conditions favor this interaction. To better understand the reaction of CC-bisulfite adduct formation (HASA), this study has evaluated the profile of 22 CCs in a "synthetic wine" containing bisulfite and in 10 real samples of different wines from the São Francisco Valley, northeastern Brazil. On the basis of principal component analysis (PCA) and dissociation constants, the results revealed that aliphatic aldehydes form adducts with S(IV), whereas ketones, cyclic aldehydes, and trans-alkenes interact weakly and are found predominantly in their free form. These results revealed also that pH 10 and 11 were defined as the most appropriate for CC-SO 2 adduct dissociation, and the total CCs were quantified reliably.

Estimate of dietary exposure to sulphites using Brazilian students as a sample population.

In Brazil, there is neither a register of the use of sulphites by the food industry nor is research being undertaken on their dietary exposure to the population. The objective of the work reported here was to estimate the dietary exposure to sulphites in two different groups of high school students, a fee-paying school group and a state school group. The data were collected through a 24-hour dietary recall, which provided estimates of sulphited foods and beverages in the diet. The Maximum Permitted Level (MPL), established by the Brazilian legislation for each of the sulphited food and beverages, was used to measure the dietary exposure to this additive. On this basis none of the students could have exceeded the Acceptable Daily Intake (ADI) of 0.70 mg SO2/kg bw/day, with a average dietary exposure of 0.07 mg SO2/kg bw/day (p<0.001), with no significant statistical difference (p=0.643) between fee-paying and state school students. Highly exposed consumers (dietary exposure to more than 50% of the ADI, or either, 0.35 mg SO2/kg bw/day, to the maximum of 0.52 mg SO2/kg bw/dia) represented 4.5% of the researched samples and reached these levels of intake due to a consumption beyond 500 ml/day of industrialized packaged fruit juices, and, in the fee-paying school, for associating its consumption with alcoholic beverages like beer and wine.

Use of a copper electrode in alkaline medium as an amperometric sensor for sulphite in a flow-through configuration.

A flow injection analysis (FIA) method has been developed for the determination of sulphite in beverages. The method is based on the amperometric detection (0.60 V vs Ag/AgCl (sat. NaCl)) of the analyte at a copper surface in an alkaline medium (1 M NaOH solution) with a manifold that incorporates flow extraction of sulphite as SO2 through a PTFE membrane. Under optimal experimental conditions the peak current response increases linearly with sulphite concentration over the range from 1.0 to 5.0 mM. The repeatability of the electrode response in the FIA configuration was evaluated as 4% ( n =20), the limit of detection of the method was 0.04 mM (S/N =3) and the analytical frequency was 50 h(-1). Since ethanol is also electroactive and permeates through the PTFE membrane, a strategy involving in a first step measurements of only ethanol by manipulating the pH of the donor stream was employed for wine samples. Then, both ethanol and sulphite were measured at the copper electrode at 0.40 V vs Ag/AgCl (sat. NaCl) and the sulphite concentration was determined by difference. Results for 3 different beverage samples (alcoholic and non-alcoholic) showed excellent agreement with the ones obtained by using a recommended procedure for sulphite analysis.

Determination of sulphite in wine by coulometric titration.

A method for the determination of both free and bound S(IV) in white wine samples by coulometric titration with electrogenerated iodine is described, the S(IV) speciation being performed by extracting SO2 from samples acidified wiith hydrochloric acid. Titrations of samples treated with NaOH led to the total S(IV) concentration, the results being in agreement with the ones obtained by the distillation procedure as well as by using the classical Monier-Williams method. An average recovery of 97% was obtained for samples spiked with S(IV) in the range 0.4-1.2 mM, which demonstrated the validity of the proposed procedure. The repeatability was 1.3% and the limit of detection was estimated as 0.01 mM. Results from direct titrations of wine added to the electrochemical cell are reported, which give indications of the stability of adducts towards the reaction with iodine.

Prevençäo do escurecimento em batatas frescas descascadas e fatiadas / Prevention of browning in fresh sliced peeled potatoes

Foram examinados métodos alternativos para prevençäo do escurecimento em batatas frescas fatiadas, sem emprego de agentes dulfitantes. A inativaçäo de enzimas pelo calor, o emprego de agentes redutores, agentes quelantes e reduçäo do teor de oxigênio na embalagem foram os meios utilizados, isoladamente ou em associaçäo, para evitar o desencadeamento das reaçöes enzimáticas. Os resultados evidenciaram que o pré-tratamento da batata fatiada, por imersäo em soluçäo contendo 0,3 por cento de ácido cítrico e 0,3 por cento de ácido ascórbico, associado a uma embalagem com baixa permeabilidade ao oxigênio, permite conservar o produto sem escurecimento e com boa textura por um período de 17 dias, sob refrigeraçäo. O controle do desenvolvimento de microrganismos foi satisfatório, durante o armazenamento, com a adiçäo de 0,2 por cento de sorbato de potássio à soluçäo de imersäo