Lia Noemi Gerschenson

Air Dehydration of Strawberries: Effects of Blanching and Osmotic Pretreatments on the Kinetics of Moisture Transport

Abstract The effect of blanching and glucose concentration before drying on the rate of moisture movement during the early stages of air dehydration of strawberries at 55 °C was studied. It was found that the effective diffusion coefficient of water in strawberries (Deff) was strongly affected by heat pretreatment, but glucose dipping after blanching caused no additional effect. Electron microscopic studies of strawberry tissues were used to explain this behavior through a modification of cellular structure, disruption of cell membranes of heat-treated fruit and subsequent cell wall alteration during the osmosis step.

Effects of processing on kiwi fruit dynamic rheological behaviour and tissue structure

Abstract The effects of blanching and osmotic dehydration on the small deformation rheological properties and structure of kiwi fruit were determined. Kiwi fruit tissue behaved as an elastic solid with storage moduli (G′) dominating the viscoelastic response (G′′/G′∼0.2). Both storage (G′) and loss (G′′)moduli were frequency independent and a clear linear viscoelastic range was evident. In general, G′ and G′′ decreased upon blanching and osmotic dehydration due to tissue damage. Structural changes caused by blanching included swelling of the cell walls and increases in the extent of cell–cell separation in the middle lamella. For atmospheric osmotic dehydration, high levels of solutes were observed within the cells which lead to a reduction of freezable water. For unripe tissue, G′ and G′′ increased with vacuum dehydration and it seemed that both cell wall integrity and cellular turgor were preserved to a greater extent than in ripe processed tissue. When calcium was added to the osmoticum during osmotic dehydration under vacuum, no differences in dynamic rheological behaviour or tissue structure were detected.

Characterisation of Fiber Obtained from Pumpkin (cucumis moschata duch.) Mesocarp Through Enzymatic Treatment

Cell wall-enriched pumpkin (Cucumis moschata Duch.) powder was submitted to enzymatic hydrolysis by cellulase or hemicellulase in order to evaluate the performance of these cell wall-degrading enzymes on that substrate. Different enzyme-substrate ratios were evaluated and the effect exerted by the buffer on cell wall polysaccharides. Cellulase produced the release of pectin macromolecules which include homogalacturonans side chains, the rhamnogalacturonan I core and rhamnogalacturonan II, in conjunction with xylogalacturonans. The content of galacturonic acid in product obtained ranged from 545 to 781 g/kg of fiber. Hemicellulases produced intense pectin hydrolysis leading to fiber-fractions with galacturonic acid contents ranging from 390 to 444 g/kg of fiber and enriched in glucose polymers as the enzyme proportion increased. Few rhamnogalacturonan-I was present.The acidic citrate buffer (pH 5.2) used for allowing enzyme activity could per se remove noncovalent cross-links like ionic bonds. As a consequence, pectin-in-extensin entanglements, pectins joined by Ca2+-bridges through the homogalacturonan side chains, and some pectins that are originally soluble in cold water due to little or no binding to the cell wall, could be removed by this citrate buffer. Enzymatic hydrolysis as well as buffer extraction produced fiber-products with an important thickening effect of aqueous systems. This effect was smaller as the ratio enzyme-substrate was increased and, in general, the fiber fractions isolated produced an in vitro glucose diffusion retardation.

Effect of certain additives on sorbate stability

Abstract The effect of several additives on sorbate stability was studied in aqueous model systems of 0.91 water activity at pH 5.0. The rate constants of sorbic acid destruction could be described by first order kinetics. Non-enzymatic browning reactions exhibited zero order kinetics and were greatly influenced by sorbic acid destruction and in all systems a correlation between the natural logarithm of sorbates retention and the increase in the absorbance at 420 nm was found. Polyphosphates and propylgallate protected sorbic acid from destruction. Ascorbic acid showed a dual behavior: in the absence of sodium nitrite, it exhibited a pro-oxidant effect. When nitrite was present, ascorbic acid behaved as a protector. In general, sucrose did not influence the rate of sorbic acid destruction and the effect of sodium nitrite was diverse. In all cases, inclusion of glycine enhanced sorbic acid destruction and browning development.

Isolation of pectin-enriched products from red beet (Beta vulgaris L. var. conditiva) wastes: composition and functional properties:

The present work was dedicated to the development of an extraction process for red beet (Beta vulgaris L. var. conditiva) by-products that preserves the high molecular weight of the macromolecules with the primary aim of waste upgrading. Our study concerns the extraction of pectin-enriched products with potential thickening properties for their usage in food formulation, as well as with some healthy physiological effect, by using citrate buffer (pH = 5.2) either alone or with enzymes (hemicellulase or cellulase) active on cell wall polysaccharide networks. Considering that red beet tissue contains ferulic acid, which cross-links pectin macromolecules through arabinose residues to anchor them into the cell wall, an alkaline pretreatment was also evaluated in order to perform polysaccharide hydrolysis in the cell wall network to accomplish higher renderings. Chemical composition and yield, as well as the in vitro glucose retention exerted by the isolated fiber products were finally analyzed.

Protease and Hemicellulase Assisted Extraction of Dietary Fiber from Wastes of Cynara cardunculus

The action of protease and hemicellulase for the extraction of fractions enriched in soluble fiber from bracts and stems of Cynara cardunculus was evaluated. Using a two-factor simplex design comprising protease amounts of 0–200 μL and hemicellulase amounts of 0–200 mg for 5 g of material, we explored the effect of a 5 h enzymatic treatment at 40 °C on the chemical composition and yield of the fractions isolated. The fractions contained inulin and pectin. In general, the protein, inulin, and polyphenol contents and also the yields were higher for fractions obtained from stems. The most marked effects were observed when enzymes were used at higher concentrations, especially for hemicellulase. The inclusion of a pre-heating step increased the yield and the inulin content for fractions isolated from bracts and stems and decreased the protein and polyphenol contents, and the galacturonic acid for bracts. These fractions, in general, contained the polyphenolic compounds monocaffeoylquinic acid, apigenin, and pinoresinol.

Chapter 3 – Carbohydrates

Dietary carbohydrates constitute a group of chemically defined substances with a range of physical and physiological properties as well as health benefits. Their primary classification is based on chemistry, i.e., the character of individual monomers, degree of polymerization, and type of linkage (α or β). The effects of conventional and emerging technologies on carbohydrate properties as well as their induced modifications during processing, extraction, and preservation procedures are discussed, with special emphasis on carbohydrates with a carbon chain length up to nine carbon atoms and to inulin and starch.

Chapter 49 – Combinational Approaches for Antimicrobial Packaging: Natamycin and Nisin

Abstract Food safety is a global priority and one of the major objectives of the current food legislation. The right combination of strategies for food industrialization, including the packaging step, ensures the achievement of that objective. New food products and new industrialization processes impose the need for the development of new packaging materials that ensure food protection and that address the changing demands of the food industry and consumers. The general perception of the importance of minimizing environmental damage has catalyzed the exploration of new biobased packaging materials, such as biodegradable and edible films, because they are environmentally friendly. In addition, consumer demand for more natural foods has promoted research about natural antimicrobials like natamycin and nisin. This chapter reviews the available information on antimicrobial packaging containing the natural antimicrobials natamycin and nisin simultaneously and, in particular, their antimicrobial effectiveness. According to published and new results evaluated, packaging containing natamycin and nisin is a very efficient strategy to control food contamination. In addition, the use of biodegradable materials to produce the packaging contributes to environment protection.