Formol Index Research Articles

FALSIFICATION OF CITRUS JUICES

The problem of falsification of juice products today is urgent due to the fact that this group of food products is consumed by all segments of the population. Today, at the same time as the presence of a wide range of juices in the modern market, it is quite difficult to identify them and prevent falsification. As a result, there is a need to strengthen control over the quality of juice products and to develop criteria for the authenticity of juices. 
 The article presents the results of the study of the quality of orange juices purchased in the retail outlets in Minsk. In order to identify and detect falsification, a comprehensive assessment of juices was carried out. The author determined the main indicators of the quality and safety of juices such as dissolved solids, titratable acidity, pH level, sugar-acid ratio. However, due to the fact that these indicators can be easily adjusted by adding organic acids, sugars and other components, a study was carried out of such indicators as the content of oxymethylfurfural and formol index, which are the most difficult to falsify. Standard and common methods were used during the experiment. The quality assessment also included an analysis of the causes of deviations 
 that could be found during the study. These causes may be explainable properties of raw materials or technological features of production.

Effect of UV–Vis processing on enzymatic activity and the physicochemical properties of peach juices from different varieties

Abstract This work evaluated the effect of ultraviolet and visible light (UV–Vis) processing on the enzymatic activity (polyphenol oxidase and peroxidase) and physicochemical characteristics (pH, °Brix, acidity, formol index, phenolics, ascorbic acid, sugars and colour) of peach juices from three different varieties (Baby Gold, Calanda and Planet Top). Irradiation was performed for 120 min, at 25 and 45 °C, using a multi-wavelength emission lamp which provided a radiation power of 4.49 · 10−2 W·cm−2 at the liquid surface. After the treatments, no significant changes were observed in the pH value, acidity, vitamin C content, sugar content, or lightness. The phenolic content was reduced for the Planet Top juices, while the formol index decreased for the Calanda variety. a* and b* CIELab parameters decreased with processing time, contrary to that reported for thermal treatments. In most cases, UV–Vis irradiation was effective at inactivating polyphenol oxidase (PPO) and peroxidase (POD), although sometimes an initial activation was observed. The inactivation stage was described by a first-order model. At 45 °C, PPO was almost totally inactivated for the three juices studied, while reductions in POD of up to 60% were registered. Further experiments are suggested to improve the effectiveness of this technology for inactivating enzymes in peach juices.

Effect of UV–Vis irradiation on enzymatic activities and the physicochemical properties of nectarine juices from different varieties

The influence of UV–Vis irradiation on some physical and chemical attributes (colour, pH, soluble solid content, formol index, total phenolic content, sugar profile and vitamin C) and enzymatic activities (polyphenol oxidase and peroxidase) of clarified nectarine juices from two different varieties (Big Top and Luciana) was studied. The samples were irradiated for 120 min using a 460-W nominal power medium-pressure mercury lamp, emitting in a range between 250 and 740 nm. Processing was performed at 25 and 45 °C. At 25 °C, none of the assayed parameters changed significantly but at 45 °C, some changes occurred in the sugar profile. Both Polyphenol oxidase and peroxidase were inactivated by up to 60% at 25 °C and completely inactivated at 45 °C for both juice varieties, and all cases fitted a first-order kinetic model.

Physicochemical Properties of Melipona beecheii Honey of the Yucatan Peninsula

<p>The knowledge regarding the physicochemical characteristics of the honey produced by stingless bees is still limited, mainly due to the high diversity of the floral resources and the low production that is inherent to these species. This manuscript describes the physicochemical characterization of 27 honey samples produced by <em>Melipona beecheii, </em>from the Yucatan Peninsula, Mexico. The objective of this study was to contribute to the establishment of standards for quality control. The following parameters were evaluated in the honey samples: reducing sugars, moisture content, acidity, pH, hydroxymethylfurfural (HMF), ash, soluble solids, formol index, proline and color. Most of physico-chemical parameters fulfilled the quality criteria established by the International Legislation for Apis honey, with the exception of moisture content, which presented higher values; for that, the results indicate that the international standard procedures are not completing adequate for all the parameters analyzed on <em>Apis mellifera</em> honey and therefore is need establish a suitable standard of quality control for honey from <em>Melipona</em>.<em> </em></p>

Effect of UV–Vis Irradiation on Enzymatic Activities and Physicochemical Properties of Four Grape Musts from Different Varieties

The influence of ultraviolet–visible irradiation on some quality attributes (pH, soluble solids content, color parameters, absorption spectrum, vitamin C, total acidity, total phenolics, formol index, and total and reducing sugars) and polyphenol oxidase, peroxidase, and pectinmethylesterase activities of fresh grape juices was investigated. Grape juice was made from two varieties of white grapes (Victoria and Dauphine) and two varieties of pink grapes (Emperor and Red Globe). Each juice was irradiated for 140 min with a high-pressure mercury lamp of 400 W that emits in a range between 250 and 740 nm. Polyphenol oxidase was not completely inactivated during irradiation, reducing only 80% of its initial activity in juices from white grapes and only 50% in those from pink grapes. On the contrary, peroxidase was completely inactivated. A slight or nonexistent variation was observed in most of the measured physicochemical parameters, showing high stability during irradiation. Only vitamin C and color had a significant variation, with an average decrease of 30% for vitamin C in all varieties and a more important variation of color parameters in the pink varieties than in the white ones.

Ultrafiltration and reverse osmosis for clarification and concentration of fruit juices at pilot plant scale

The process of ultrafiltration of raw juices (peach, pear, apple and mandarin) through tubular polysulphone membranes (8 kDa) and finally concentrated by reverse osmosis membranes of tubular composite polyamide film (99 g/100 g NaCl rejection) with filtration area of 0.9 m2 was studied. Furthermore, in order to obtain a higher permeate flow, the fluids were previously treated with commercial pectinolytic enzyme.The following parameters were analyzed: permeate flow, soluble solids, viscosity, density, pH, acidity, formol index, starch, pulp content, color and presence of pectin. The use of a pectinolytic enzyme provides increased permeate flux of approximately 40%, retaining the juice properties. The highest total soluble solids content was clarified peach juice from 12.2 °Brix concentrated up to 30.5 and 21.52 °Brix by using RO with transmembranes pressures of 4 and 2 MPa respectively.The results show a cross-flow velocity (1.8 m/s) which corresponds with Reynolds number that is on the lower border of a laminar flow and above of transition rate (2090 < Re < 2900). Also the (VCF) for mandarin (1.49), pear (1.53), apple (1.56) and peach (1.58) was obtained for RO process. The membranes used were characterized morphologically using scanning electron microscopy.

Physicochemical characteristics of organic honey samples of africanized honeybees from Parana River islands

This research was carried out to evaluate the physicochemical composition of organic honey in Parana River islands, in Porto Brasilio, State of Parana. Honey was harvested directly from super of the colonies in three apiaries spread in the Floresta and Laranjeira Islands, from August 2005 to August 2006. Twenty-four samples of organic honey produced by Africanized honeybees were evaluated. The following parameters were analyzed: pH, acidity, formol index, hydroxymethylfurfural, ashes, color, electric conductivity and moisture. Three replications per sample were performed for laboratorial analysis, giving the means and standard deviation. Most honey samples were in conformity with the Normative Instruction 11 from October 20, 2000. However, 4.17% were not in accordance with the moisture standards, 8.33% showed high concentrations of hydroxymethylfurfural, thus, totalizing 12.50% of non-complying samples. Nevertheless, 87.50% of the analyzed honey samples are within the standards, being characterized as an organic product of excellent quality, with good commercialization perspectives in the market.

Physicochemical characteristics and pollen spectra of organic and non-organic honey samples of Apis mellifera L.

The aim of this research was to analyze and compare 17 honey samples, 11 organic and six non-organic Apis mellifera honey. The samples were analyzed concerning moisture, hydroxymethylfurfural, diastase index, water activity, color, total sugar, reducing sugar, sucrose, ash, viscosity, electrical conductivity, pH, acidity, and formol index. With the exception of acidity, reducing sugar and diastase index, the averages of other parameters were different between the two groups. All samples of organic honey presented moisture values between 23.50 and 24.40%. Among the nonorganic honey samples, two presented apparent sucrose amount upper the maximum limit established by the Brazilian Legislation. According to the quantitative analysis of pollen sediments in the honey samples and frequency of pollen types in 17 honey samples, 41.20% were classified as unifioral, and the remainder as polifioral.

Physico-chemical characteristics of honey produced by Apis mellifera in the Picos region, state of Piauí, Brazil

The objectives of this research were to determine physico-chemical characteristics of 1,758 Apis mellifera L. honey samples produced by in the productive pole of Picos, state of Piaui, to understand, based on these characteristics, how they are grouped and to determine the percentage of honey that fit the specifications determined by Brazilian legislation. Thirty-five honey samples were collected directly from beekeepers for determination of total sugars, reducing sugars, apparent sucrose, humidity, diastase activity, hydroxymethylfurfural (HMF), protein, ash, pH, acidity, formol index, electrical conductivity, viscosity and color. Mean values of each one of the analyzed physico-chemical parameters are within the limits established by the current Brazilian legislation, but it was verified for apparent sacarosis, diastase activity and HMF, values different from the established ones. Protein and HMF were the traits that contributed most for group formation.

DEGRADATION OF MANDARIN JUICE CONCENTRATES TREATED AT HIGH TEMPERATURES

ABSTRACT This work aims to characterize nonenzymatic browning of concentrated mandarin juice treated at different temperatures, identifying the different factors involved and their influence, and to propose a kinetic model for their evolution with treatment time. For 65°Brix sample, at 98C, the evolution of carotenes and total sugars can be described by means of first‐order kinetics, and formol index changes according to zero‐order kinetics. In the case of 5‐hydroxymethylfurfural, two types of kinetics, first‐order and autocatalytic, were assayed. For the mandarin juices at different temperatures (70–98C) and concentrations (10–65°Brix), the absorbance A440 decreases according to first‐order kinetics. For the highest treatment temperatures and the most concentrated samples, in the first stage, an increase in the brightness and decrease of A440attributed to carotene degradation is observed. After the carotenes disappear, an increase in the color is observed, probably caused by the Maillard reaction.PRACTICAL APPLICATIONSIn order to obtain some kinetic of deterioration processes of thermal‐processed juice, it is necessary to use high sufficient times to see its evolution. In some procedures for obtaining marmalades and jams using commercial fruit juices, cooking times tend to be high, which will negatively affect the quality of the final product. It is in these cases in which they could use the kinetic data obtained with high time treatment. In the nonenzymatic browning kinetic models determination, it is convenient to perform studies with sufficient high times assuring the possibility to interpolate the residence time of the juice while it flows through the heat treatment device. The information obtained from the study could be used as a guideline for designing thermal processes to reduce the quality degradation of the mandarin juice concentrates.

Propriedades físicas e químicas do mel de Apis mellifera L

O presente trabalho teve como objetivo verificar as propriedades físicas e químicas do mel da região Sul do Estado do Tocantins a partir de 24 amostras provenientes de 13 associações de apicultores. As análises realizadas foram pH, acidez, índice de refração, umidade, peso específico, cinzas, hidroximetilfurfural (Prova qualitativa), índice de formol, reação de Lund e açúcares redutores. Todas as análises foram realizadas em triplicata, o tratamento estatístico compreendeu média, desvio padrão e os resultados foram submetidos à análise fatorial e análise de agrupamento. As amostras apresentaram índice de reprovação de 50% aos padrões estabelecidos pela legislação. A grande variação nos resultados entre as amostras podem ser devido a diferentes origens florais dos méis e a sua inadequação à legislação pode ter origem na exposição do produto a condições de temperatura e umidade inadequadas, nas etapas de manejo, processamento ou armazenamento do mel.

Effect of UV irradiation on enzymatic activities and physicochemical properties of apple juices from different varieties

The influence of ultraviolet irradiation (UV) on some quality attributes (colour, pH, soluble solids content, formol index, total phenolics, sugars and vitamin C) and enzymatic activities (polyphenol oxidase, peroxidase and pectinolytic enzymes) of fresh apple juice was investigated. Apple juices made from four different varieties (Golden, Starking, Fuji and King David) were irradiated during 120 min with a high-pressure mercury lamp of 400 W that emits in a range between 250 and 740 nm with a resulting incident energy of 3.88·10 −7 E·min −1. The treatment was effective in the inactivation of the assayed enzymes. Polyphenol oxidase was inactivated in 100 min, while peroxidase was completely destroyed in only 15 min in all the four varieties. No variations were observed in pH, soluble solids content, formol index, total phenolics and sugars. The colour of the juice made from King David was unvariable during all the experiment. In the ones made from Golden, Starking and Fuji, UV radiation impaired some of the pigments present in the juice, either initially present or the ones formed later. This fact can be especially observed in the increase of the CIELab parameter L*, which increased from 23.2 to 24.6 in Fuji juice. The content of vitamin C in juices from Golden, Starking and Fuji slightly changed during the experiment, decreasing a 4.0% in Fuji juice, 5.7% in Golden one and 5.6% in Starking one. Meanwhile, in the juice from King David the loss was 70.0%. This significant difference can be attributed to the lack of pigmentation of this juice.

Chemical characterisation of Crataegus azarolus L. fruit from 14 genotypes found in Tunisia

SummaryFruits from genotypes of 14 Crataegus were collected at the full-ripe stage at three locations in Tunisia. Fresh fruit juice was analysed for some chemical properties. The juice content [% (v/w)], pH, titratable acidity (g malic acid 100 ml−1), and formol index (ml NaOH 100 ml−1 juice), and the contents of total soluble solids (°Brix), total sugars [(g 100 g−1 fresh fruit weight (FW)], reducing sugars (g 100 g−1 FW), and salts (mg 100 g−1 FW), were established as: 2.0 – 11.9%, 3.2 – 4.2, 0.9 – 1.9, 2.8 – 4.4, 16.3 – 21.5, 5.3 – 17.0, 5.8 – 7.9, and 0.6 – 0.7, respectively. Fresh juice also contained vitamin C (31.4 mg ascorbic acid 100 g−1 FW, and the mineral elements; calcium (285.6 – 399.1 mg 100 g−1 FW), sodium (30.4 – 43.8 mg 100 g−1 FW), and potassium (138.5 – 169.2 mg 100 g−1 FW). The concentration of phenols ranged from 498.5 – 1,477 mg 100 g−1 FW. This study showed great variation between fruit from the 14 genotypes. Principal component analysis and hierarchical cluster analysis allowed the separation of hybrids of Crataegus species and varieties. Two groups and three sub-groups were identified. Eight genotypes were distinguished as C. azarolus var. aronia, and two others as C. azarolus var. eu-azarolus. The two genotypes of C. oxyacanthus ssp. monogyna were completely different from the other genotypes. Two genotypes were putative hybrids: C. azarolus var. eu-azarolus C. azarolus var. aronia, and C. oxyacanthus ssp. monogyna C. azarolus var. aronia. Fruit from C. oxyacanthus ssp. monogyna exhibited the highest phenol contents, and red-coloured fruit from C. azarolus var. eu-azarolus also showed high phenol content, whereas most C. azarolus var. aronia genotypes, with yellow fruit, had the highest percentage of juice and low phenol contents. Our results demonstrate the opportunity to improve and select genotypes of C. azarolus, especially those having fruit with high vitamin C and phenol contents with high anti-oxidant activities.

Effect of storage period under variable conditions on the chemical and physical composition and colour of Spanish refrigerated orange juices

The effects of the physicochemical and quality characteristics of various minimally pasteurized refrigerated orange Spanish juices and their changes with storage time and temperature were investigated. Essential oils, acidity, conductivity, diacetyl index, hydroxymethylfurfural, formol index, viscosity and ascorbic acid varied with storage time more significantly at 10 °C than at 4 °C. Density, colour and pectinmethylesterase did not vary at 4 °C. Some of the parameters could be used as indicators of quality loss or spoilage of the juices. The degradation kinetics of the concentration of remaining ascorbic acid against time follows a straight line whose slope indicates the degradation rate. A period of at least 42 days at 4 °C and 35 days at 10 °C was established as the shelf life of the juices.

Análise de agrupamento, com base na composição físico-química, de amostras de méis produzidos por Apis mellifera L. no Estado de São Paulo

A composição do mel depende, basicamente, da composição do néctar de cada espécie vegetal produtora, conferindo-lhe características específicas enquanto que as condições climáticas e o manejo do apicultor têm influência menor sobre essas características. A presente pesquisa, desenvolvida com amostras de méis de Apis mellifera coletadas diretamente dos produtores de 84 municípios do Estado de São Paulo teve o objetivo de verificar, com base em características físico-químicas, como se agrupam as amostras de méis silvestres e de eucaliptos. Dentre as 121 amostras de méis analisadas as de eucaliptos e as silvestres formam grupos distintos quanto aos caracteres físico-químicos, o que confirma que a origem floral interfere decisivamente nas características dos méis. Pela análise dos componentes principais, pode-se verificar que os caracteres que mais influenciaram no agrupamentos das amostras de méis foram condutividade elétrica e quantidade de K, no eixo X e índice de formol e umidade, no eixo Y.

Quality characteristics of horchata (a Spanish vegetable beverage) treated with pulsed electric fields during shelf-life

The application of pulsed electric fields (PEF) is one of the new non-thermal technologies being studied to evaluate their potential as alternative or complementary processes to thermal pasteurization. “Horchata de chufa” (tiger nut milk or earth almond milk) is of high nutritional quality and therefore has great potential in the food market, limited by its very short shelf-life. The present work studies whether PEF can be used to obtain a quality horchata and increase its shelf-life while maintaining its organoleptic characteristics. In order to do so we determined pH, total fat, peroxide index, thiobarbituric acid-reactive substances index, formol index, and peroxidase activity in natural (untreated) horchata and horchata subjected to various PEF treatments and studied their stability during refrigerated storage (2–4 °C). After PEF treatment, only peroxidase activity decreased significantly ( p < 0.05). This parameter and pH varied during the shelf-life of the horchata, and a negative correlation was obtained between pH and peroxidase activity.

Physicochemical Characteristics and Quality of Refrigerated Spanish Orange‐Carrot Juices and Influence of Storage Conditions

ABSTRACT: The effects of the physicochemical and quality characteristics of various refrigerated mixed orange and carrot juices, and their changes with storage time and temperature were investigated. Density, dry extract, Brix values, acidity, turbidity, formol index, pectinmethylesterase, hydroxymethylfurfural, essential oils, ascorbic acid, and color varied with storage time and temperature. Some of the parameters could be used as indicators of quality loss or spoilage of the juices. The degradation of ascorbic acid corresponded to 1st‐order kinetics. The shelf life of the juices was established at 4 °C and 50‐d storage or at 10 °C and 32‐d storage.

Kinetics of colour development in aqueous glucose systems at high temperatures

Non-enzymatic browning was studied in aqueous model systems containing glucose and aspartic acid, glutamic acid or asparagine at three different solid concentrations (15%, 30% and 45% by weight) which were heat treated for different times at four temperatures (85°C, 90°C, 95°C and 100°C). Some indicators were used to evaluate the extent of the Maillard reaction: spectrophotometric measurements at 280 and 420 nm ( A 280 and A 420), formation of 5-(hydroxymethyl)-2-furfural (HMF) and CIE, L ∗,a ∗,b ∗ parameters. The pH and the formol index were also determined. The indicators A 280, A 420 and HMF formation showed that the kinetic constant values increased when increasing the heat-treatment temperature while the influence of solid concentration was not clear. After a short induction period, the data were well correlated to zero-order kinetics. With reference to colourless intermediate formation ( A 280 and HMF), aspartic acid turned out to be the most reactive amino acid while in brown pigment formation, it was asparagine. Glutamic acid was the least reactive amino acid for both processes. The activation energy was found to range from 110 to 180 kJ/mol for both, intermediate and brown pigment formation.

Kinetics of colour development in aqueous fructose systems at high temperatures

Non-enzymatic browning was studied in aqueous model systems containing fructose and aspartic acid, glutamic acid or asparagine at three different soluble solid concentrations (150, 300 and 450 g kg−1), which were heat treated for different times at four temperatures (85, 90, 95 and 100 °C). Various indicators were used to evaluate the extent of the Maillard reaction: spectrophotometric measurements at 280 and 420 nm (A280 and A420) and CIE (Commission Internationale de l'Eclairage) parameters L* (lightness), a* (redness), b* (yellowness) and ΔE* (colour difference, which is expressed as [(Δa*)2 + (Δb*)2 + (ΔL*)2]1/2). The pH and the formol index were also determined. The indicator for colourless intermediate formation, A280, showed that the kinetic constant values increased with increasing heat treatment temperature, while the influence of soluble solid concentration was not clear. After a short induction period the data were well described by assuming zero-order kinetics. Glutamic acid turned out to be the most reactive amino acid, while asparagine was the least reactive. With reference to brown pigment formation, A420 and ΔE*, glutamic acid was the least reactive amino acid. In all the experiments assayed, except for glutamic solutions with fructose concentrations of 150 and 300 g kg−1, the data were best correlated with combined kinetics. © 2000 Society of Chemical Industry

Nota. Cinética de pardeamiento no enzimático de zumo de pera concentrado Note./ Non-enzymatic browning kinetics of concentrated pear juice

Non-enzymatic browning kinetics of concentrated juice for three pear varieties (Alexandrine Douillard, Flor de Invierno and Blanquilla) was evaluated at three temperatures (90, 80 and 70 °C) and different soluble solid contents (52, 62 and 72 °Brix). The evolution of absorbance at 420 nm is described by zero order kinetics, but the formation of 5-hydroxymethyl-2 furfuraldehyde (HMF) and the reduction in formol index followed first order kinetics. The Alexandrine Douillard juices showed non-enzymatic browning which was less pronounced than in Flor de Invierno and Blanquilla juices.