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FT-Raman spectroscopy has been explored as a quick screening method to evaluate the presence of lactose and identify milk powder samples adulterated with maltodextrin (2.5–50% w/w). Raman measurements can easily differentiate samples of milk powder, without the need for sample preparation, while traditional quality control methods, including high performance liquid chromatography, are cumbersome and slow. FT-Raman spectra were obtained from samples of whole lactose and low-lactose milk powder, both without and with addition of maltodextrin. Differences were observed between the spectra involved in identifying samples with low lactose content, as well as adulterated samples. Exploratory data analysis using Raman spectroscopy and multivariate analysis was also developed to classify samples with PCA and PLS-DA. The PLS-DA models obtained allowed to correctly classify all samples. These results demonstrate the utility of FT-Raman spectroscopy in combination with chemometrics to infer about the quality of milk powder.

As shelf life of pasteurized milk is relatively short the application of microfiltration was investigated as a way to increase milk shelf life. Raw milk was microfiltered and stored in bottles or pasteurized and stored in packages made from one of three different low density polyethylene (LDPE) multilayer films or a LDPE monolayer film. The results proved the efficiency of the 0.8 μm-microfiltration process in increasing shelf life of milk to at least 30 d with a reduction of the total microorganism count to a range of 5 log10. Specific properties of the various films led to different results concerning the barrier of the packages; however these differences did not have great influence on the shelf life of pasteurized milk. Evaluated packaging materials proved to provide sufficient protection to pasteurized milk and allow it to maintain its quality; therefore, the least expensive film may be chosen for use in commercial application.

Heat treatment is commonly used in dairy technology. Usually, milk is heated and cooled many times before to obtain the final product and milk components are then subject to cumulative heat treatments. In the present work, we investigated the heat induced aggregation (90 °C until 24 h) of two model proteins, β-lactoglobulin (β-Lg) and β-casein (β-CN), in the presence of glucose and subsequent consequences on simulated gastro-duodenal digestion. Protein aggregation and digestion were monitored using polyacrylamide gel electrophoresis, size exclusion chromatography, dynamic light scattering and transmission electron microscopy. Concomitant heating and protein glycation affect aggregation kinetics as well as protein sensitivity to enzymatic digestion. Spherical covalently linked aggregates were favored in the case of β-CN in the presence of glucose. Glucose limited the formation of twisted fibrils from β-Lg. We clearly showed that aggregates of both proteins formed in the presence of glucose were more resistant to enzymatic digestion. Those formed from β-Lg being highly resistant and still present at the end of simulated gastro-duodenal process. These findings underline the importance not only of the aggregation as such but also of the nature of formed aggregates on protein digestibility.

BACKGROUND: The plastic crates used in fruit and vegetable shipping can be vehicles of disease dissemination among production fields, since there is a chance of phytopathogenic micro-organism adhesion on the crate surfaces when in contact with soil, contaminated produce or handling. The aim of this study was to develop an active plastic crate incorporated with a triclosan-based antimicrobial agent and to evaluate its efficiency of micro-organism inhibition. RESULTS:Staphylococcus aureus (a human pathogen), Clavibacter michiganensis ssp. michiganensis and Erwinia carotovora ssp. carotovora (phytopathogens) were the most sensitive micro-organisms when in contact with samples of plastic crate incorporated with 30 g kg−1 of antimicrobial agent. They presented diameters of approximately 5.0, 3.5 and 3.5 cm respectively in the halo test. Mean specific growth rates decreased in samples with 30 g kg−1 of antimicrobial agent, compared with control samples, from 1.13 to 0 h−1 for S. aureus, from 1.26 to 0.47 h−1 for Escherichia coli and from 1.75 to 0.18 h−1 for Listeria monocytogenes. The antimicrobial agent did not influence the mechanical properties of the crates. CONCLUSION: The active plastic crate has great potential to contribute to the safety of horticultural produce by restraining the proliferation of micro-organisms among production fields. Copyright © 2008 Society of Chemical Industry

The objective of this study was to evaluate the effect of ozone (O3) treatment on postharvest quality of pear cv. ‘Williams’. Pears were exposed to gaseous ozone at the concentration of 100 ppm for 60 minutes in a flow rate of 2.3 L min-1 and stored in BOD incubators at 25 ± 2°C, 75-85 % relative humidity, for 13 days. Fruit quality was evaluated at the beginning and at days 3, 6, 9 and 13 of storage for the following variables: Fresh Mass Loss (FML), Titratable Acidity (TA), Total Soluble Solids (TSS), pH and microbiological examination (total aerobic mesophilic count and total yeast and mold count). The variables Fresh Mass Loss (FML) and Total Soluble Solids (TSS) were significantly affected by the ozone treatment. In general, the microorganism counts in ozonatedpears were lower than those in untreated pears. The treatment with gaseous ozone increased the shelf life of the pears with efficient microorganism control, did not affect the quality parameters pH and titratable acidity and delayed soluble solids increase.

Esse trabalho teve como objetivo avaliar a qualidade físico-química, microbiológica e sensorial da banana ozonizada por via seca e por via úmida. Para o tratamento por via seca, os frutos foram fumigados diretamente com ozônio por 30 minutos. Para o tratamento da banana por via úmida, efetuou-se a ozonização da água por 20 min, e em seguida imersão dos frutos na água ozonizada por 10 min. Em ambos os tratamentos a concentração do gás e a vazão utilizadas foram 0,36 mg L-1 e 1,5 L min-1, respectivamente. A qualidade dos frutos foi avaliada no início do armazenamento e aos 3; 6; 9 e 12 dias. Analisaram-se as variáveis: perda de massa fresca (PMF), acidez total titulável, sólidos solúveis totais, pH, relação polpa/casca, índice de cor da casca, severidade de podridões, análise microbiológica (contagem total de fungos e leveduras) e análise sensorial. Em geral, os frutos imersos em água ozonizada foram os que apresentaram melhor qualidade ao longo do armazenamento, tanto no que se refere aos parâmetros físico-químicos quanto aos microbiológicos, e tiveram boa aceitação sensorial entre os provadores. Dessa forma, concluiu-se que o tratamento com água ozonizada é uma nova alternativa para manejo pós-colheita de banana. This study was done to analyze the physic-chemical, microbiological and sensory qualities of the banana, after being either dry or wet treatment with ozone. For dry processing, the fruits were directly fumigated with ozone for 30 min. The wet treatment included the ozonization of water for 20 min followed by immersion of the fruit in the ozonized water for 10 min. In both treatments, the utilized gas concentration and flow were 0.36 mg L-1 and 1.5 L min-1, respectively. The quality of the fruits was evaluated at the beginning of storage and after 3; 6; 9 and 12 days. The variables analyzed were: fresh mater loss, total titratable acidity, total soluble solids, pH, pulp/peel ratio, color index of the peel, rot severity, microbiological analysis (total fungi and yeast count) and sensorial analysis. In general, the fruits immersed in the ozonized water presented better quality, in reference to both the physico-chemical and microbiological parameters, as well as have good sensory acceptance among those tested. It could therefore be concluded that treatment with ozonized water is a new alternative for the postharvest handling of bananas.

The behavior of β-lactoglobulin (β-Lg) during heat treatments depends on the environmental conditions. The influence of the presence or absence of a reducing sugar, namely, glucose, on the modification of the protein during heating has been studied using fluorescence, polyacrylamide gel electrophoresis (PAGE), size-exclusion chromatography (SEC), and transmission electron microscopy. Glycated products were formed during heating 24 h at 90 °C and pH 7. The fluorescence results revealed an accumulation of the advanced Maillard products and the formation of aggregates during heating. PAGE and SEC data suggested that the products in the control samples were essentially composed of covalently linked fibrillar aggregates and that their formation was faster than that for glycated samples. We showed that glucose affected the growing step of covalent aggregates but not the initial denaturation/aggregation step of native protein. Glucose-modified proteins formed a mixture of short fibrils and polydisperse aggregates. Our results revealed that β-Lg forms fibrils at neutral pH after heating and that glucose slows the formation of these fibrils.

A Brazilian ham-flavored cream cheese was developed using gamma-irradiated beetroot extract as the colorant. An irradiation dose of 5.0 kGy was used based on previous studies that indicated no growth of moulds, yeasts and aerobic psychotropic microorganisms during 12 days at 5 °C, and with no changes in the structure of the pigment. One part of the cheese was colored with the irradiated beetroot extract and the other part with carmine cochineal, which is a natural stable colorant but expensive and difficult to extract. Both portions were submitted to sensory evaluation with 67 panelists. No significant differences were found in flavor and overall appearance. The cream cheese containing carmine cochineal was slightly preferred in regards to color. However, being a new product, these results were encouraging and point towards the potential use of irradiated beetroot extract as a natural food colorant.

The European PREMIUM project aims at proposing new eco-friendly strategies to preserve lactic acid bacteria (LAB). One approach considered is the development of new protective agents in order to allow the application of more aggressive drying processes than freeze-drying. Recently, oligosaccharides such as fructo-oligosaccharides and galacto-oligosaccharides have been reported as promising molecules for protecting LAB. It is generally assumed in the literature that direct interaction between membrane and protective agent is important to stabilize membrane during water removal. The ability of oligosaccharides to interact with bacterial membrane will be dependent not only on their sugar composition but also on the lipid membrane composition. The objective of this study is to develop a simplified lipid model representative of bacterial membrane to investigate the specific interaction between oligosaccharides and lipids. The membrane of two strains of lactic acid bacteria exhibiting different freezing resistances and extremely low survival to freeze-drying were fully characterized to determine lipid composition and lipid phase transition. Lipid membrane models of various level of complexity were subsequently designed: i) liposomes and monolayers from bacterial lipid extracts; ii) liposomes from lipid extracts enriched with standard lipids, and ii) liposomes and monolayers made from two standard lipids. The standard lipids were chosen in accordance with the predominant lipids present within the bacterial membrane. The biophysical properties of these models were determined using Fourier Transform Infrared spectroscopy (lipid phase transition) and Langmuir isotherms (surface pressure area isotherms). Two binary lipid models satisfactorily representing the two bacterial strains according to their biophysical properties were set up and could thus be further used to investigate specific interaction between lipid and oligosaccharides.