Effects of short-wave ultraviolet light, ultrasonic and microwave treatments on banana puree during refrigerated storage.

Enzymatic browning is a major problem in minimally processed banana puree; it reduces consumer's acceptability and affects nutritional quality. The objective of this work was to evaluate the effects ultrasound (40 kHz/10 min), microwave (800 W/ 25 s) and UV-C radiation (1.97 kJ/m2) applied to banana puree. Colour parameters (L*, a*, b*, chroma and hue), browning index (BI), polyphenol oxidase (PPO) and peroxidase (POD) activities, total phenolic compounds (TPC), antioxidant capacity (AOC) and microbiological counts were monitored throughout storage at 4 °C. Ultrasound (US) and microwave (MW) treatments achieved a significant (p < 0.05) reduction in PPO activity and BI; moreover, ultrasound effectively retained phenolic compounds content (75% of initial value). The AOC was in coincidence with TPC values. POD activity was partially inhibited by UV-C while MW and US increase its activity. Although UV-C treatment was not effective to control browning development, it was effective to maintain microbiological stability after 20 days of storage (1.48 ± 0.01 log CFU/g). The evaluated treatments have the advantage of being less aggressive than conventional thermal treatments while maintaining fresh characteristics of the product.

Phosphate Fertilization as a Modulator of Enzymatic Browning in Minimally Processed Cassava.

This study proposes to relate the increase in phosphorus (P) supply in the soil, via phosphate fertilization, to oxidative damage and protection, phenylpropanoid metabolism, and enzymatic browning in minimally processed cassava. The roots were grown with 0, 60, and 120 kg ha-1 P2O5. The roots were harvested, and the yield and P content in the root, stem, and leaves were quantified. The roots were minimally processed and stored for 12 days at 5 °C. The higher supply of P in the soil increased the P content of roots and stems but not the agro-industrial yields. Roots grown at 120 kg ha-1 P2O5 showed higher detection of hydrogen peroxide, which was accompanied by increased phenolic compounds, soluble quinones, and antioxidant capacity and increased activities of the enzymes superoxide dismutase, catalase, ascorbate peroxidase, polyphenol oxidase, and peroxidase. The present study thus demonstrates the role of phosphorus application, induction of the synthesis of phenolic compounds, and quality of fresh-cut cassava.

Occurrence of acrylamide and other heat-induced compounds in panela: Relationship with physicochemical and antioxidant parameters.

Panela is a natural, unrefined non-centrifugal sugar obtained by intense dehydration of sugarcane juice. Acrylamide, hydroxymethylfurfural (HMF), and furfural were determined in 40 panela samples distributed as granulated and block according to the technological process. Colour, browning, moisture, water activity, pH and antioxidant capacity were also evaluated. Acrylamide ranged between 60 and 3058 µg/kg; granulated panela reporting the highest concentration (812 µg/kg) compared with block panela (540 µg/kg). The lower content in HMF and furfural, the intense dehydration, and the extensive darkening of granulated panela suggested the browning reactions were boosted due to the application of more severe thermal treatments. Principal component analysis showed a significant relationship between the panela presentation and the concentration of the analysed compounds. Benchmark values considering both types of processes would help to establish mitigation initiatives in panela products. The chromatic parameter a* could be used as an indirect index of the acrylamide content in panela.

Purification and biochemical characterization of polyphenol oxidase from soursop (Annona muricata L.) and its inactivation by microwave and ultrasound treatments.

The soursop (Annona muricata L.) is a climacteric fruit that may undergo enzymatic browning during ripening, mainly by the activity of polyphenol oxidase (PPO). Soursop PPO was purified 160-fold by hydrophobic interaction and ion-exchange chromatography. The native structure has a molecular weight of 112 kDa corresponding to a dimeric structure. The protein has an optimum pH and temperature of 6.5 and 25°C, respectively; and activation energy of 40.97 kJ·mol-1 . The lowest Km value was observed for caffeic acid (0.47 mM); the best substrate was 4-methyl-catechol (1,067 U·mM-1  min-1 ). Inactivation assays showed that PPO was completely inactivated by tropolone, Na2 S2 O5 and ascorbic acid, and thermally at 55°C for <5 min, microwave exposure reduced activity to 57% at 70 W in 30 s and ultrasound treatment diminished activity to 43% at 120 W in 220 s. This study allows a better understanding of soursop PPO behavior and provides inactivation information. PRACTICAL APPLICATIONS: The conservation of fresh fruits is complicated due to the enzymatic reactions that are present in fruits, such as enzymatic browning. The enzymes responsible for these reactions can be inactivated by, different chemical compounds as well as by the use of emerging technologies, such as microwaves and sonication, which seek to satisfy the consumer needs to obtain fresh products with good nutritional characteristics and adequate safety.

Reduced Enzymatic Browning in Potato Tubers by Specific Editing of a Polyphenol Oxidase Gene via Ribonucleoprotein Complexes Delivery of the CRISPR/Cas9 System.

Polyphenol Oxidases (PPOs) catalyze the conversion of phenolic substrates to quinones, leading to the formation of dark-colored precipitates in fruits and vegetables. This process, known as enzymatic browning, is the cause of undesirable changes in organoleptic properties and the loss of nutritional quality in plant-derived products. In potato (Solanum tubersoum L.), PPOs are encoded by a multi-gene family with different expression patterns. Here, we have studied the application of the CRISPR/Cas9 system to induce mutations in the StPPO2 gene in the tetraploid cultivar Desiree. We hypothesized that the specific editing of this target gene would result in a lower PPO activity in the tuber with the consequent reduction of the enzymatic browning. Ribonucleoprotein complexes (RNPs), formed by two sgRNAs and Cas9 nuclease, were transfected to potato protoplasts. Up to 68% of regenerated plants contained mutations in at least one allele of the target gene, while 24% of edited lines carried mutations in all four alleles. No off-target mutations were identified in other analyzed StPPO genes. Mutations induced in the four alleles of StPPO2 gene, led to lines with a reduction of up to 69% in tuber PPO activity and a reduction of 73% in enzymatic browning, compared to the control. Our results demonstrate that the CRISPR/Cas9 system can be applied to develop potato varieties with reduced enzymatic browning in tubers, by the specific editing of a single member of the StPPO gene family.

Non-enzymatic browning kinetics in sucrose-glycine aqueous and dehydrated model systems in presence of MgCl2.

The development of non-enzymatic browning in the presence of MgCl2 was evaluated in liquid and dehydrated sucrose-glycine model systems, in relation to interactions of the salt with water and/or with sucrose. In both systems, browning was accelerated by the presence of MgCl2 because of the increased sugar hydrolysis (ten times faster) and the reduction of water mobility (1H NMR T2 relaxation times) caused by this salt (between 6 and 14% lower), counteracting the inhibitory effect of water on the Maillard reaction. MgCl2 also provoked a 40% reduction on the fluorophores quantum yield, responsible also of the fluctuations observed in the fluorescence development as a function of time after 50 h at 70 °C. Molecular and supramolecular effects of the presence of MgCl2 have been observed on the Maillard reaction kinetics. These results are of high technological interest when strategies to control the Maillard reaction rate are required for a particular application.

Effect of formulation and baking conditions on the structure and development of non-enzymatic browning in biscuit models using images.

The aim of this research was to determine the effect of composition (dietary fiber = DF, fat = F, and gluten = G) and baking time on the target microstructural parameters that were observed using images of potato and wheat starch biscuits. Microstructures were studied Scanning Electron Microscope (SEM). Non-enzymatic browning (NEB) was assessed using color image analysis. Texture and moisture analysis was performed to have a better understanding of the baking process. Analysis of images revealed that the starch granules retained their native form at the end of baking, suggesting their in complete gelatinization. Granules size was similar at several different baking times, with an average equivalent diameter of 9 and 27 µm for wheat and potato starch, respectively. However, samples with different levels of DF and G increased circularity during baking to more than 30%, and also increasing hardness. NEB developed during baking, with the maximum increase observed between 13 and 19 min. This was reflected in decreased luminosity (L*) values due to a decrease in moisture levels. After 19 min, luminosity did not vary significantly. The ingredients that are used, as well as their quantities, can affect sample L* values. Therefore, choosing the correct ingredients and quantities can lead to different microstructures in the biscuits, with varying amounts of NEB products.

Enzymatic browning in avocado (Persea americana) revisited: History, advances, and future perspectives.

Considering nearly 80 years of research regarding one of the enzymes responsible for catalyzing the formation of pigments in higher animals, plants, fungi and bacteria, this review will focus on collecting and categorizing the existing information about polyphenol oxidase (PPO) in fruits, with particular emphasis on the information in relation to avocado, which is one of the hardiest species in terms of inactivation, has documented dual activity (EC 1.14.18.1/EC 1.10.3.1), and represents one of the oldest challenges for food science research and fruit processors. It is expected that this review will contribute to the further development of the field by highlighting the questions that have arisen during the characterization of PPO, the progress that has been made and the questions that remain today, in addition to new methodologies that are being applied to study this system. Holistic methodologies offer unexplored potential for advancing our understanding of the complex phenomena that govern PPO activity in fruits, because these methodologies will enable the characterization of this family of enzymes in all of its complexity. Subsequently, it will be possible to develop better techniques for controlling enzymatic browning in this valuable fruit.

Evaluation of antioxidant capacity in coffees marketed in Colombia: Relationship with the extent of non-enzymatic browning.

Fifty-eight samples of commercial Colombian coffee with different characteristics (soluble, ground, decaffeinated, etc) were evaluated for antioxidant capacity (AC) (ABTS and FRAP), total soluble phenolics (TP), browning index (BI), color parameters (L(∗), a(∗), b(∗), c(∗) and h(∗)), HMF and furfural. The AC in Colombian coffees was very varied (164-1000, 100.8-885.9µmol of Trolox equiv/g and 12.5-127mg gallic acid equiv/g, respectively for ABTS, FRAP and TP). AC, TP, BI, color, HMF and furfural values were higher (p<0.05) in soluble coffees than in ground ones, showing the lyophilized samples which showed the highest average values. Significant lineal correlations (p<0.05) were found between AC and color parameters, BI, HMF. No significant (p<0.05) differences in the AC between the different types of coffee were found. This work confirms the direct relationship between the rate of non-enzymatic browning and antioxidant capacity.

Purification and partial biochemical characterization of polyphenol oxidase from mango (Mangifera indica cv. Manila).

Polyphenol oxidase (PPO) is an enzyme widely distributed in the plant kingdom that has been detected in most fruits and vegetables. PPO was extracted and purified from Manila mango (Mangifera indica), and its biochemical properties were studied. PPO was purified 216-fold by hydrophobic interaction and ion exchange chromatography. PPO was purified to homogeneity, and the estimated PPO molecular weight (MW) by SDS-PAGE was ≈31.5 kDa. However, a MW of 65 kDa was determined by gel filtration, indicating a dimeric structure for the native PPO. The isolated PPO showed the highest affinity to pyrogallol (Km = 2.77 mM) followed by 4-methylcatechol (Km = 3.14 mM) and catechol (Km = 15.14 mM). The optimum pH for activity was 6.0. PPO was stable in the temperature range of 20-70 °C. PPO activity was completely inhibited by tropolone, ascorbic acid, sodium metabisulfite, and kojic acid at 0.1 mM.

Effect of active packages on enzymatic browning in fresh-cut potatoes (solanum tuberosum) / Efeito de embalagens ativas no escurecimento enzimático de batatas (solanum tuberosum) fatiadas e minimamente processadas

The modern life has increased the demand for fresh-cut fruits and vegetables, which maintain closer characteristics to in natura, beyond the convenience and be ready-to-use. The effect of active packages in the browning inhibition of fresh-cut potatoes was estimate. 30 micra cellulosic films with ascorbic + citric acid addition (2, 3 e 5% each one), sodium metabisulphite (0,3 ; 0,5 e 1%) and the control (without anti-browning agent). The control treatment with film (without agent) and without film presented increase on pH after storage from 5,7 to 6,7 while potatoes with AA + AC antioxidants addition demonstrated a little decrease to 5,5. Potatoes treatments with AA + AC antioxidants in the films maintained the initial color by all storage period, while potatoes with sodium metabisulphite in the films exhibited a strong browning. This effect for the films with antioxidants addition happened because the decrease on pH, below the optimum point for enzyme activity, improving to reduce the relative enzyme activity lower to 50%, considering then the film with antioxidants addition being more effective to control the enzymatic browning, acting on polyphenoloxidase inhibition.    

A vida moderna tem aumentado a demanda por frutas e hortaliças minimamente processadas, que mantêm características próximas ao in natura, além da praticidade e conveniência. Foi avaliado o efeito de embalagens ativas na inibição do escurecimento de batatas fatiadas minimamente processadas. Filmes de base celulósica, com 30 micras de espessura, foram incorporados com a mistura ácido ascórbico + ácido cítrico (2, 3 e 5% de cada), antioxidante metabissulfito de sódio (0,3 ; 0,5 e 1,%) e o controle (sem agente anti-escurecimento). As amostras de batatas envolvidas em filme (sem agente) e sem filme apresentaram aumento de pH de 5,7 para 6,7 após armazenamento, enquanto batatas envolvidas em filmes com adição de compostos químicos apresentaram diminuição de pH para 5,5. Os filmes incorporados com as misturas de AC e AA mantiveram a coloração inicial da batata durante o período de estocagem, enquanto que os filmes contendo metabissulfito de sódio apresentaram escurecimento intenso das batatas. Este efeito para os filmes com adição de antioxidantes ocorreu em razão da diminuição do pH, abaixo do ponto ótimo de atividade desta enzima, conseguindo reduzir a atividade relativa da enzima à menos de 50%, considerando o filme com adição de antioxidantes sendo mais efetivo no controle do escurecimento enzimático, agindo na inibição da enzima polifenoloxidase.   

Effect of active packages on enzymatic browning in fresh-cut potatoes (solanum tuberosum) / Efeito de embalagens ativas no escurecimento enzimático de batatas (solanum tuberosum) fatiadas e minimamente processadas

The modern life has increased the demand for fresh-cut fruits and vegetables, which maintain closer characteristics to in natura, beyond the convenience and be ready-to-use. The effect of active packages in the browning inhibition of fresh-cut potatoes was estimate. 30 micra cellulosic films with ascorbic + citric acid addition (2, 3 e 5% each one), sodium metabisulphite (0,3 ; 0,5 e 1%) and the control (without anti-browning agent). The control treatment with film (without agent) and without film presented increase on pH after storage from 5,7 to 6,7 while potatoes with AA + AC antioxidants addition demonstrated a little decrease to 5,5. Potatoes treatments with AA + AC antioxidants in the films maintained the initial color by all storage period, while potatoes with sodium metabisulphite in the films exhibited a strong browning. This effect for the films with antioxidants addition happened because the decrease on pH, below the optimum point for enzyme activity, improving to reduce the relative enzyme activity lower to 50%, considering then the film with antioxidants addition being more effective to control the enzymatic browning, acting on polyphenoloxidase inhibition.

A vida moderna tem aumentado a demanda por frutas e hortaliças minimamente processadas, que mantêm características próximas ao in natura, além da praticidade e conveniência. Foi avaliado o efeito de embalagens ativas na inibição do escurecimento de batatas fatiadas minimamente processadas. Filmes de base celulósica, com 30 micras de espessura, foram incorporados com a mistura ácido ascórbico + ácido cítrico (2, 3 e 5% de cada), antioxidante metabissulfito de sódio (0,3 ; 0,5 e 1,%) e o controle (sem agente anti-escurecimento). As amostras de batatas envolvidas em filme (sem agente) e sem filme apresentaram aumento de pH de 5,7 para 6,7 após armazenamento, enquanto batatas envolvidas em filmes com adição de compostos químicos apresentaram diminuição de pH para 5,5. Os filmes incorporados com as misturas de AC e AA mantiveram a coloração inicial da batata durante o período de estocagem, enquanto que os filmes contendo metabissulfito de sódio apresentaram escurecimento intenso das batatas. Este efeito para os filmes com adição de antioxidantes ocorreu em razão da diminuição do pH, abaixo do ponto ótimo de atividade desta enzima, conseguindo reduzir a atividade relativa da enzima à menos de 50%, considerando o filme com adição de antioxidantes sendo mais efetivo no controle do escurecimento enzimático, agindo na inibição da enzima polifenoloxidase.

Effect of antioxidants in fresh cut radishes during the cold storage

The objective of this study was to evaluate the efficiency of antioxidants in the cold storage of fresh cut radishes. The shredded roots were submerged in the respective treatments during 3 min (ascorbic acid or citric acid) and stored at 5ºC and 90 percent RH during 10 days. The radish treated with ascorbic acid showed the higher respiratory rate in the first 4 h after the processing during the storage. The content of total soluble solids (TSS) was significantly higher in the treatment with citric acid. There was an increase in the content of ascorbic acid after two day of storage in the treatments with this antioxidant. The values of lightness (L*) were decreasing along the storage. Citric acid treatments caused strongly red coloration in the minimally processed roots. None of the treatments avoided the browning of the shredded radishes during the cold storage.

O presente experimento objetivou testar o uso de antioxidantes na conservação de rabanetes minimamente processados. Os rabanetes minimamente processados foram submersos nos tratamentos por 3 minutos (ácido ascórbico ou ácido cítrico) e armazenados a 5ºC (±1ºC) e 90 por cento (±5 por cento) UR durante 10 dias. O tratamento com ácido ascórbico gerou a maior taxa respiratória nas 4 primeiras horas após o processamento e durante o armazenamento. O teor de sólidos solúveis totais (SST) foi significativamente maior no tratamento com ácido cítrico. Quanto ao teor de ácido ascórbico, para os tratamentos com ácido ascórbico houve um aumento significativo no 2º dia. Os valores de luminosidade (L*) apresentaram redução durante o armazenamento. Os tratamentos com ácido cítrico provocaram uma forte coloração vermelha nas raízes minimamente processadas. Nenhum dos tratamentos evitou o escurecimento das raízes de rabanete minimamente processadas.

Use of active films in the minimally processed potato conservation / Uso de filmes ativos na conservação de batata minimamente processada

Potatoes of the variety Monalisa were minimally processed like slices and submitted to different treatments, employed to decrease the enzymatic browning and growth of microorganisms. These treatments consisted on pure cellulose films (FP) or incorporated with active compounds (2% of citric acid (AC), 0,5% of L-cysteine Hydrochloride Monohydrate (CIS), 7% of sorbic acid (AS) and film incorporated with all of them (MIS)) which were intercalated to sliced potatoes. For control, potatoes were conditioned without film. All of the samples were conditioned in expanded polystyrene trays, wrapped up in PVC film and stored 8ºC ± 2ºC by nine days. Every three days, they were evaluated for color, pH, water activity (Aw) and microbiological quality (growth of total Coliformes and to 45ºC, Molds and yeasts, Psychrotrophics, Bacillus cereus and Staphylococcus positive coagulase). The treatments didnt differ significantly (p>0,05) for most of the evaluated parameters, except for the color difference, that presented significant difference to the 10% of probability. In conclusion, the active films can minimize the enzymatic browning of vegetables.

Batatas da variedade Monalisa, foram fatiadas e minimamente processadas e, após, cobertas por filmes ativos, empregados para minimizar o escurecimento enzimático e o crescimento de microrganismos. Utilizaram-se filmes celulósicos incorporados com aditivos (2% de ácido cítrico (AC), 0,5% de monocloridrato de L-cisteína (CIS), 7% de ácido sórbico (AS) e mistura dos compostos mencionados (MIS)) ou sem a incorporação destes (Filme FP), que foram intercalados às batatas fatiadas. Como controle, foram utilizadas batatas mantidas sem filme intercalado (SF). Todas as amostras foram acondicionadas em bandejas de poliestireno expandido, envoltas em filme de PVC e armazenadas por 9 dias a 8ºC ± 2ºC. A cada três dias, as amostras de batatas foram avaliadas quanto à cor, pH, atividade de água (Aa) e qualidade microbiológica (contagem de Coliformes totais e a 45ºC, Fungos filamentosos e leveduras, Psicrotróficos, Bacillus cereus e Staphylococcus coagulase positiva). Observou-se que para os mesmos tempos de estocagem, os tratamentos não diferiram significativamente (p>0,05) para a maioria dos parâmetros avaliados, com exceção da diferença de cor, onde diferiram significativamente aos 10% de probabilidade. Conclui-se que os filmes ativos anti escurecimento têm potencial de serem usados em vegetais que apresentam deterioração por escurecimento enzimático.    

Use of active films in the minimally processed potato conservation / Uso de filmes ativos na conservação de batata minimamente processada

Potatoes of the variety Monalisa were minimally processed like slices and submitted to different treatments, employed to decrease the enzymatic browning and growth of microorganisms. These treatments consisted on pure cellulose films (FP) or incorporated with active compounds (2% of citric acid (AC), 0,5% of L-cysteine Hydrochloride Monohydrate (CIS), 7% of sorbic acid (AS) and film incorporated with all of them (MIS)) which were intercalated to sliced potatoes. For control, potatoes were conditioned without film. All of the samples were conditioned in expanded polystyrene trays, wrapped up in PVC film and stored 8ºC ± 2ºC by nine days. Every three days, they were evaluated for color, pH, water activity (Aw) and microbiological quality (growth of total Coliformes and to 45ºC, Molds and yeasts, Psychrotrophics, Bacillus cereus and Staphylococcus positive coagulase). The treatments didnt differ significantly (p>0,05) for most of the evaluated parameters, except for the color difference, that presented significant difference to the 10% of probability. In conclusion, the active films can minimize the enzymatic browning of vegetables.

Batatas da variedade Monalisa, foram fatiadas e minimamente processadas e, após, cobertas por filmes ativos, empregados para minimizar o escurecimento enzimático e o crescimento de microrganismos. Utilizaram-se filmes celulósicos incorporados com aditivos (2% de ácido cítrico (AC), 0,5% de monocloridrato de L-cisteína (CIS), 7% de ácido sórbico (AS) e mistura dos compostos mencionados (MIS)) ou sem a incorporação destes (Filme FP), que foram intercalados às batatas fatiadas. Como controle, foram utilizadas batatas mantidas sem filme intercalado (SF). Todas as amostras foram acondicionadas em bandejas de poliestireno expandido, envoltas em filme de PVC e armazenadas por 9 dias a 8ºC ± 2ºC. A cada três dias, as amostras de batatas foram avaliadas quanto à cor, pH, atividade de água (Aa) e qualidade microbiológica (contagem de Coliformes totais e a 45ºC, Fungos filamentosos e leveduras, Psicrotróficos, Bacillus cereus e Staphylococcus coagulase positiva). Observou-se que para os mesmos tempos de estocagem, os tratamentos não diferiram significativamente (p>0,05) para a maioria dos parâmetros avaliados, com exceção da diferença de cor, onde diferiram significativamente aos 10% de probabilidade. Conclui-se que os filmes ativos anti escurecimento têm potencial de serem usados em vegetais que apresentam deterioração por escurecimento enzimático.