Purpose -The purpose of this study was to investigate the polyphenoloxidases (PPO) activities in Jerusalem artichoke tubers as well as their inactivation. The following are important for the processing of this food: treatment and conversion used in preserving processes. Design/methodology/approach -The PPO of whole tubers and the separated tuber skins as determined using a modified PPO essay with 0.01 M dopamine.HCl as reactant and photometry (DA 470 plotted against reaction time up to 3 min). Nine varieties used in German tuber production were in the test.Findings -The highest enzyme activity of PPO was in the skin, range from 1,274 up to 3,026 nkat. In the pulps of the tubers nearly traces of PPO could be detected (range: 2 up to 5 nkat). The inhibition of PPO activity in tuber homogenates was investigated in simulated processes which were used in the food industry: heat (drying, pasteurisation) and oxidase inhibitors such as lemon juice, ascorbic and/ or citric acid. The optimum temperature of PPO was 608C and the inactivation occurred at 858C. The range of the PPO activity was between pH 5 and 10, with the optimum at pH 7.0. Lemon juice is a natural inhibitor of the PPO activity in fruit and vegetable juices containing Jerusalem artichoke as well as in canning the tubers. Lemon juice combined with citric acid and ascorbic acid is recommended against enzymatic browning reaction. Originality/value -The characterisation of the parameters which influence enzymatic browning of Jerusalem artichoke tubers during food processing: heat and pH, have not been described before.
Cet article des Editions Lavoisier est disponible en acces libre et gratuit sur sda.revuesonline.comSeparation and Identification of Phenolic Compounds in Jerusalem Artichoke (Helianthus tuberosus L.) 395© Lavoisier -La photocopie non autorisée est un délit SUMMARYSeveral methods such as colorimetry, reversed-phase high performance liquid chromatography (RP-HPLC), the coupling of liquid chromatography and gas chromatography with mass spectrometry (LC-MS, GC-MS) were examined for their suitability and applied to the separation, identification and quantification of phenolic compounds in different varieties of Jerusalem artichoke. Twenty two phenolic compounds have been separated, identified and quantitated as gallic acid (from 1 mg up to 140 mg), protocatechuic acid (from 5 mg up to 200 mg), esculin (from 4 mg up to 270 mg), gentisic acid (from 30 mg up to 3 g), catechin (from 1mg up to 300 mg), 4-hydroxybenzoic acid (from 1 mg up to 90 mg), chlorogenic acid (from 20 mg up to 5 g), vanillic acid (from 1 mg up to 520 mg), syringic acid (from 1 mg up to 40 mg), caffeic acid (from 1 mg up to 240 mg), epicatechin (from 4 mg up to 800 mg), 2-hydroxy-3-5-dinitrobenzoic acid (from 2 mg up to 140 mg), umbelliferon (from 2 mg up to 110 mg), scopoletin (from 1 mg up to 80 mg), p-cumaric acid (from 1 mg up to 40 mg), cumaric-3-carbon acid (from 1 mg up to 40 mg), ferulic acid (from 1 mg up to 40 mg), sinapic acid (from 1 mg up to 60 mg), 3-hydroxycinnamic acid (trace) ; ellagic acid (from 2 mg up to 40 mg), 4-hydroxycumarin (from 4 mg up to 300 mg) and salicylic acid (from 30 mg to 7 g). These phenolics contents are expressed for 100 g tubers or skins dry weight.Twenty of the identified phenolic compounds are of interest in the medicine and with diets.
High alcohol wines have become a major challenge in the international wine trade. Several physical processes are used to produce wines with reduced-alcohol content, all of which involve the selective extraction of ethanol based on volatility or diffusion. In this study, the possibility of Gluzyme Mono ® 10.000 BG (Gluzyme) (Novozymes, South Africa) to reduce the glucose content of synthetic grape juice before fermentation was investigated in order to produce wine with reduced-alcohol content. Gluzyme is a glucose oxidase preparation from Aspergillus oryzae, currently used in the baking industry. Glucose oxidase catalyses the oxidation of glucose to gluconic acid and hydrogen peroxide (H 2 O 2) in the presence of molecular oxygen. Gluzyme was initially used in synthetic grape juice, where different enzyme concentrations and factors influencing its efficiency were investigated under winemaking conditions. The results showed up to 0.5% v/v less alcohol at an enzyme concentration of 20 kU compared to the control samples. This reduction in alcohol was increased to 1 and 1.3% v/v alcohol at pH 3.5 and pH 5.5 respectively in aerated (8 mg/L O 2) synthetic grape juice using 30 kU enzyme. Secondly, Gluzyme was used to treat Pinotage grape must before fermentation. Gluzyme-treated wines at 30 kU enzyme concentration after fermentation contained 0.68% v/v less alcohol than the control wines. A decrease in acetic acid concentration of the treated compared to control wines was also observed.
O cultivo de morango é caracterizado pelo uso indiscriminado de agrotóxicos, o que pode causar não apenas contaminação alimentar, mas também o acúmulo de resíduos no ambiente e no homem. Técnicas que minimizem as concentrações residuais nos produtos e no ambiente são desejadas. Assim, este trabalho visou avaliar a utilização de lodo biológico de estações de tratamento de esgoto doméstico no cultivo de morango na degradação do fungicida tebuconazol (TEB) no solo, sua influência nas concentrações residuais e na atividade microbiana no solo. O experimento foi feito usando um planejamento experimental do tipo central composite design (CCD) com 10 tratamentos, sendo: fatoriais (combinações dos níveis +1 e -1), centrais (nível 0) e pontos axiais (+1,41 e -1,41). Foram realizadas análises físico-químicas e microbiológicas no solo e análises cromatográficas para detecção de resíduos de TEB no solo e no morango. Os resultados evidenciaram que maiores dosagens de TEB aplicadas ao cultivo de morango resultaram em maiores concentrações residuais desse fungicida no solo, porém não afetaram os teores residuais no fruto. A adição de lodo biológico ao solo durante o cultivo de morango resultou em maior atividade da biomassa microbiana, melhorando a estabilidade do solo. A destinação de lodo biológico ao solo durante o cultivo de morango mostrou-se adequada e resultou em melhoria na atividade microbiana do solo, o que pode proporcionar benefícios ambientais e econômicos.
A degradação de pesticidas em solos pode ser avaliada como uma possível solução para minimizar os efeitos da ação tóxica destes compostos recalcitrantes em alimentos cultivados e no meio em que ocorre este cultivo. Uma alternativa comum e sustentável é o uso de lodo ativado de esgoto doméstico tratado (LET) como coadjuvante em solos. O objetivo deste trabalho foi avaliar a influência do LET no perfil de degradação de um pesticida no solo. Partindo da hipótese de que o uso de LET em solos pode influenciar na degradação de pesticidas, foi implementada uma abordagem lab-to-field para determinação do decaimento do analito tóxico utilizando o difenoconazol (DFC), um fungicida da classe dos triazóis. Foram testadas duas técnicas para extração e clean-up das amostras e, para cada técnica foram testados dois solventes. Também otimizadas as condições cromatográficas por cromatografia gasosa acoplada a espectrometria de massas (CGEM) para identificação dos principais íons e quantificação do DFC. O experimento foi feito em quatro vasos contendo: somente solo; solo e LET na proporção 70/30%, respectivamente; solo fortificado com DFC; e solo e LET na proporção 70/30%, respectivamente, fortificado com DFC. Para o estudo da degradação foram retiradas alíquotas dos vasos durante 21 dias após dosagem de DFC na concentração de 20 mg.Kg-1, respeitando frequência de coleta estabelecida. O método considerado mais eficiente para determinação de DFC utilizou extração com diclorometano sob ultrassom e clean up com a técnica de extração dispersiva em fase sólida, utilizando alumina como adsorvente. A partir dos resultados analíticos e da construção das curvas de degradação dos dois vasos que continham o analito, verificou-se que no primeiro dia após a dosagem houve uma queda brusca na concentração de DFC em ambos vasos, com mais intensidade no substrato só com solo. Nos dias seguintes o substrato com solo e LET apresentou maior decaimento do DFC em relação ao substrato com solo, confirmando variação significativa entre os substratos.
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