Christine M. Oliver

Use of Power Ultrasound to Improve Extraction and Modify Phase Transitions in Food Processing

In recent years, the physical and chemical effects of ultrasound in liquid and solid media have been extensively used in food processing applications. Ultrasound in liquids generates a number of physical forces. Vibration, pressure, and physical agitation are forces that can be generated in the absence of acoustic cavitation. In addition to these physical forces, acoustic cavitation generates microjets, shear forces, shockwaves, radical formation, and acoustic streaming. At lower frequencies (20–100 kHz), the physical effects dominate. At intermediate frequencies (200–500 kHz), chemical effects (formation of highly reactive radicals within the cavitation bubbles) are more dominant, as the number of active bubbles generated is higher. At higher frequencies (>1 MHz), cavitation and the associated chemical effects are less likely and acoustic streaming effects are dominant. There are a number of food processing applications where these physical and chemical forces of ultrasound have been found to be effective. The present review summarizes selected areas of food applications such as extraction, crystallization, thawing, drying, and freezing where ultrasound is found to be beneficial in terms of increasing efficiency, reducing time, and increasing the yields. The reason for choosing these applications is that such areas are not critically reviewed in the existing literature.

Insight into the Glycation of Milk Proteins: An ESI- and MALDI-MS Perspective (Review)

Protein-reducing sugar conjugates are formed by the naturally occurring Maillard reaction, otherwise known as glycation. The Maillard reaction products (MRP) formed can provide novel and/or improved functionality compared to the unmodified protein. Understanding the chemistry of the Maillard reaction, the physicochemical properties of its products, and, more importantly, the inter-relationships between these properties and the specific functionality of a given MRP will help to define the potential of MRP as food ingredients in their own right. Recently, electrospray ionization-mass spectrometry (ESI-MS) and matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) have acquired a leading role in the structural characterization of proteins. The ability of these techniques to provide detail about the nature and extent of protein modifications at a molecular level as well as conformational information provides new insight into the glycation process. This article reviews the role that ESI- and MALDI-MS have played in advancing our understanding of the glycation of milk proteins.

Degradation of Curcuminoids by in Vitro Pure Culture Fermentation

Colonic bacteria may mediate the transformation of curcuminoids, but studies of this metabolism are limited. Here, the metabolism of curcuminoids by Escherichia fergusonii (ATCC 35469) and two Escherichia coli strains (ATCC 8739 and DH10B) was examined in modified medium for colon bacteria (mMCB) with or without pig cecal fluid. LC-MS analysis showed that 16-37% of curcumin, 6-16% of demethoxycurcumin (DMC) and 7-15% of bis-demethoxycurcumin (Bis-DMC), and 7-15% of bis-demethoxycurcumin (Bis-DMC) were converted following 36 h of fermentation, with the amount of curcuminoids degraded varying depending on the bacterial strain and medium used. Three metabolites (dihydrocurcumin (DHC), tetrahydrocurcumin (THC), and ferulic acid (FA)) were found in fermentation cultures with all strains used. In addition, a compound with m/z [M - H](-) 470 was found and identified to be a curcumin adduct (curcumin-l-cysteine), using accurate mass FT-ICR-MS. This study provides insights into the bacterial metabolism of curcuminoids.

Impact of extra virgin olive oil and ethylenediaminetetraacetic acid (EDTA) on the oxidative stability of fish oil emulsions and spray-dried microcapsules stabilized by sugar beet pectin.

The influence of EDTA on lipid oxidation in sugar beet pectin-stabilized oil-in-water emulsions (pH 6, 15% oil, wet basis), prepared from fish oil (FO) and fish oil-extra virgin olive oil (FO-EVOO) (1:1 w/w), as well as the spray-dried microcapsules (50% oil, dry basis) prepared from these emulsions, was investigated. Under accelerated conditions (80 °C, 5 bar oxygen pressure) the oxidative stability was significantly (P < 0.05) higher for FO and FO-EVOO formulated with EDTA, in comparison to corresponding emulsions and spray-dried microcapsules formulated without EDTA. The EDTA effect was greater in emulsions than in spray-dried microcapsules, with the greatest protective effect obtained in FO-EVOO emulsions. EDTA enhanced the oxidative stability of the spray-dried microcapsules during ambient storage (~25 °C, a(w) = 0.5), as demonstrated by their lower concentration of headspace volatile oxidation products, propanal and hexanal. These results show that the addition of EDTA is an effective strategy to maximize the oxidative stability of both FO emulsions and spray-dried microcapsules in which sugar beet pectin is used as the encapsulant material.

Synergism between ultrasonic pretreatment and white rot fungal enzymes on biodegradation of wheat chaff

Lignocellulosic biomass samples (wheat chaff) were pretreated by ultrasound (US) (40kHz/0.5Wcm(-2)/10min and 400kHz/0.5Wcm(-2)/10min applied sequentially) prior to digestion by enzyme extracts obtained from fermentation of the biomass with white rot fungi (Phanerochaete chrysosporium or Trametes sp.). The accessibility of the cellulosic components in wheat chaff was increased, as demonstrated by the increased concentration of sugars produced by exposure to the ultrasound treatment prior to enzyme addition. Pretreatment with ultrasound increased the concentration of lignin degradation products (guaiacol and syringol) obtained from wheat chaff after enzyme addition. In vitro digestibility of wheat chaff was also enhanced by the ultrasonics pretreatment in combination with treatment with enzyme extracts. Degradation was enhanced with the use of a mixture of the enzyme extracts compared to that for a single enzyme extract.

An overview of the development and applications of nanoscale materials in the food industry

Abstract: Nanotechnology involves the study and use of materials at the nanoscale. Nanotechnology has been shown to cover many aspects of the food industry, including the development of new and improved food packaging materials, advanced food security devices and sensors to improve food quality, and food products with prolonged shelf-life, new tastes, textures and health benefits. Nanotechnology-derived food and food ingredients are anticipated to demonstrate enormous growth worldwide and already a range of ingredients, carriers and food-contact materials are available in the market. This chapter provides an overview of ‘top-down structuring’ and ‘bottom-up structuring’ processes that can be used to create nanostructures from food components and assemble nanostructured materials for use in the food, beverage and nutraceutical industries. The potential benefits of nanotechnology applications in the food, beverage and nutraceutical industries are reviewed and examples of existing products mentioned. Emerging trends in nanotechnology within the food sector are also considered.

Use of Milk Proteins for Encapsulation of Food Ingredients

Dairy proteins are highly valued as encapsulating materials. They have many inherent functional properties, including their ability to stabilize emulsions and form gel matrices, which enable them to function as effective encapsulants. They may be used to encapsulate a wide range of hydrophilic and hydrophobic food ingredients, as well as probiotic microorganisms. Milk proteins may be used alone or in combination with other food ingredients such as carbohydrates, gums, surfactants, and lipids for formulating encapsulated food ingredients and food bioactives. This chapter reviews the use of milk proteins in the formulation and processing of encapsulated food ingredients. It includes examples of encapsulated food ingredients formulated with milk proteins as encapsulating materials, alone or in combination with other food materials, from the scientific and patent literature. It highlights the versatility of milk proteins for encapsulation of food ingredients.

Sequential low and medium frequency ultrasound assists biodegradation of wheat chaff by white rot fungal enzymes.

The consequences of ultrasonic pre-treatment using low (40 kHz) and medium (270 kHz) frequency (40 kHz followed by 270 kHz) on the degradation of wheat chaff (8 g 100ml(-1) acetate buffer, pH 5) were evaluated. In addition, the effects of the ultrasonic pre-treatment on the degradation of the wheat chaff when subsequently exposed to enzyme extracts from two white rot fungi (Phanerochaete chrysosporium and Trametes sp.) were investigated. Pre-treatment by sequential low and medium frequency ultrasound had a disruptive effect on the lignocellulosic matrix. Analysis of the phenolic-derived volatiles after enzymatic hydrolysis showed that biodegradation with the enzyme extract obtained from P. chrysosporium was more pronounced compared to that of the Trametes sp. The efficacy of the ultrasonic pre-treatment was attributed to increased enzyme accessibility of the cellulose fibrils due to sonication-induced disruption of the plant surface structure, as shown by changes in the microstructure.