Search

Thesis (Master)--İzmir Institute of Technology, Biotechnology and Bioengineering, İzmir, 2005, Includes bibliographical references (leaves: 73-75), Text in English; Abstract: Turkish and English, xiv, 92 leaves, In this study, the radical scavenging and iron chelating capacity of proteins from heat treated (20 min at 90 oC) or thermally processed (20 min at 121 oC) chick-peas andkidney-beans were compared. Lyophilized crude protein extracts from chick-peas contained more protein (1.5-3 fold) and showed higher free radical scavenging (up to 2.3 fold) and iron binding capacity (up to 3 fold) than lyophilized crude protein extracts form kidney-beans. The thermal processing of chick-peas did not cause a significant change in the radical scavenging capacity of their lyophilized crude protein extracts, but improved the iron chelating capacity of these proteins almost 80 %. However, the thermal processing reduced both the radical scavenging and iron binding capacity of crude lyophilized proteins form kidney beans by 20-40 % and 60 %, respectively.Partial purification by ammonium sulfate precipitation or DEAE-cellulose chromatography increased the antioxidant capacity of thermally processed chick-pea proteins. The DEAE cellulose chromatography also showed the presence of 5 and 3 antioxidant protein fractions in heat treated and thermally processed chick-peas, respectively. Hot acidic hydrolysis at 80 oC for 30 min in presence of 1.5 M HCl increases the specific antioxidant activity of protein extracts, but causes the formation of undesired Maillard reaction products. Hot extraction at 85 oC for 30 min at pH 2.5 extracts the antioxidant proteins selectively, whereas 85 oC for 30 min at pH 9.5 extracts both antioxidant proteins and other proteins.

The antimicrobial and antioxidant potential of zein and zein-wax composite films having different release profiles for lysozyme and mixture of lysozyme, catechin and gallic acid were tested on cold-stored fresh Kashar cheese inoculated with Listeria monocytogenes ATCC 7644. All lysozyme containing films prevented the increase of L. monocytogenes counts in Kashar cheese for 8 weeks at 4°C, but it was only the zein-wax composite films with sustained lysozyme-release rates which caused a significant reduction (- 0.4 decimals) in initial microbial load of inoculated cheese samples. The mixture of catechin and gallic acid improved the in vitro antimicrobial effect of films against L. monocytogenes, but showed no considerable antimicrobial effect in cheese. However, the films containing catechin and gallic acid were effective in preventing oxidative changes in cheese. This study showed the possibility of increasing safety and quality of fresh cheeses by use of active packaging employing natural antimicrobial compounds and controlled release technology. Industrial relevance There has been a growing interest to develop the functional properties of packaging materials and to obtain packed foods with better shelf-life and quality. Active packaging incorporating antimicrobials is one of the most promising areas since application of this method can improve safety of foods by inhibiting pathogenic bacteria or controlling spoilage flora by using minimum amounts of active compounds. Recently, health concerns of consumers and environmental problems related to plastics increased the popularity of using natural antimicrobial substances in edible films and coatings. This work employs a GRAS status natural antimicrobial lysozyme and zein a major by-product of rapidly growing oil and bioethanol industries which can form self-standing films, coatings or casings. The results of this study showed the possibility of using flexible antimicrobial and antioxidant films with controlled release properties in diary industry., Scientific and Technical Research Council of Turkey (108M353)

To eliminate their classical brittleness and flexibility problems zein films were plasticized by incorporation of different phenolic acids (gallic acid (GA), p-hydroxy benzoic acid (HBA) or ferulic acids (FA)) or flavonoids (catechin (CAT), flavone (FLA) or quercetin (QU)). The use of GA, CAT, FA and HBA at 3mg/cm2 eliminated the brittleness of films and gave highly flexible films showing elongations between 135% and 189%, while FLA and QU caused no considerable effect on film elongation. The films containing FA and HBA showed extreme swelling and lost their structural integrity when hydrated in distilled water. In contrast, CAT and GA containing films maintained their integrity following hydration. Most of the GA (up to 93%) and a considerable portion of CAT (up to 60%) in the films existed in soluble form. Therefore, the films showed antioxidant and/or antimicrobial activity. The TEACs of soluble phenolic compounds in 3mg/cm2 CAT and GA containing films were 21.0 and 86.2μmoltrolox/cm2, respectively. The GA containing films showed antimicrobial activity on Listeria monocytogenes and Campylobacter jejuni, while CAT showed no antimicrobial activity on these bacteria at the studied concentration. This work opens a new perspective for using zein in flexible bioactive packaging., Scientific and Technical Research Council of Turkey (108M353)

This study investigated the effects of controlled pepsin hydrolysis on antioxidant potential and fractional changes of chickpea protein extracts (CPE). The enzyme hydrolysis increased soluble protein content (1.2 to 2-fold) and free radical scavenging activity (1.9 to 3-fold) of hydrolyzed chickpea protein extract (HCPE), but almost unaffected its antioxidant potential in oil-in-water emulsion system and reduced its iron chelating capacity (1.3-fold) and functional properties. The chromatographic fractions of CPE are mainly acidic, while those of HCPE are mainly basic and neutral. The majority of chickpea proteins had pI between 4.5 and 5.5, and molecular weight (MW) between 15 and 40 kDa, while MW of their pepsin hydrolysis products ranged between 6.5 and 14.2 kDa. The main antioxidant proteins in CPE and HCPE fractionated by ultrafiltration had MW greater than 30 kDa and between 2 and 10 kDa, respectively. The chickpea proteins and hydrolysates showed different potentials as functional food ingredients. © 2009 Elsevier Ltd. All rights reserved., Izmir Institute of Technology (Project # 2004 IYTE 05)

Total antioxidant activities based on ABTS free radical scavenging activity and phenolic content of fresh or dry hazelnuts, walnuts and pistachios assayed with their seed coats changed between 3063 and 11,076 μmol trolox equivalents/100 g d.w. and 256 and 755 mg gallic acid equivalents/100 g d.w., respectively. The walnuts used in this study showed the highest antioxidant activity, followed by pistachios and hazelnuts. The removal of seed coat reduced the total antioxidant activity of hazelnuts, walnuts and pistachios almost 36, 90 and 55%, respectively. The total antioxidant activities of investigated fresh and dry nuts are not considerably different. However, phenolic content and antioxidant activity in hydrophilic and ethanolic fractions obtained by successive extraction of nuts showed some variation. The antioxidant activity in 1-serving portion of fresh or dry walnuts is equivalent to that in almost 2-serving portions of black tea, and 1.2–1.7-serving portions of green and Earl Grey tea. One-serving portions of dry hazelnuts and fresh or dry pistachios contained antioxidant activity equivalent to that in 0.7–1-serving portions of black tea. The antioxidant activity measurements correlated with phenolic content ( r 2 = 0.70). This study showed the potential of using fresh or dry nuts to develop functional foods with high antioxidant activity.

To develop edible films having controlled release properties for multiple bioactive compounds, hydrophobicity and morphology of zein films were modified by blending zein with oleic (C18:1)Δ9, linoleic (C18:2)Δ9,12, or lauric (C12) acids in the presence of lecithin. The blend zein films showed 2-8.5- and 1.6-2.9-fold lower initial release rates for the model active compounds, lysozyme (LYS) and (+)-catechin (CAT), than the zein control films, respectively. The change of fatty acid chain length affected both CAT and LYS release rates while the change of fatty acid double bond number affected only the CAT release rate. The film morphologies suggested that the blend films owe their controlled release properties mainly to the microspheres formed within their matrix and encapsulation of active compounds. The blend films showed antilisterial activity and antioxidant activity up to 81 μmol Trolox/cm2. The controlled release of multiple bioactive compounds from a single film showed the possibility of combining application of active and bioactive packaging technologies and improving not only safety and quality but also health benefits of packed food., Scientific and Technical Research Council of Turkey (108M353)

The aim of this study was controlled release of lysozyme by modification of hydrophobicity and morphology of zein films using composite and blend film making methods. The incorporation of beeswax, carnauba or candelilla wax into films at 5% (w/w) of zein gave composite films containing amorphous wax particles, while incorporation of oleic acid into film at 5% of zein caused formation of blend films containing many spherical zein capsules within their matrix. The lysozyme release rates of composites reduced as the melting point of waxes increased. The composites and blends showed 2.5 to 17 fold lower lysozyme release rates than controls. The films were effectively plasticized by using catechin. The catechin also provided antioxidant activity of films (up to 69 mu mol Trolox/cm(2)) and contributed to their controlled release properties by reducing film porosity. The films showed antimicrobial activity against Listeria innocua. This work showed the possibility of obtaining advanced edible films having flexibility, antimicrobial and antioxidant activity and controlled release properties., Scientific and Technical Research Council of Turkey (108M353)

In this study, antimicrobial films were developed against Campylobacter jejuni by incorporation of gallic acid (GA) into zein-based films. The zein and zein-wax composite films containing GA between 2.5 and 10 mg/cm 2 were effective on different C. jejuni strains in a concentration-dependent manner. Zein and zein-wax composite films showed different release profiles in distilled water but quite similar release profiles at solid agar medium. Depending on incorporated GA concentration, 60-80% of GA released from the films, while the remaining GA was bound or trapped by film matrix. The GA at 2.5 and 5 mg/cm 2 caused a considerable increase in elongation (57-280%) of all zein films and eliminated their classical flexibility problems. The zein-wax composite films were less flexible than zein films, but the films showed similar tensile strengths and Young's modulus. Scanning electron microscopy indicated different morphologies of zein and zein-wax composite films. This study clearly showed the good potential of zein and GA to develop flexible antimicrobial films against C. jejuni., TÜBİTAk (108M353)

The antimicrobial activity of edible films from whey proteins, alginate, zein and chitosan incorporated with polylysine (PL) and PL- ethylenediaminetetraacetic acid (Na 2EDTA) combination have been tested on different bacteria including Escherichia coli, Listeria innocua, Salmonella Typhimurium and Stapylococcus aureus. The PL-containing films of whey proteins, alginate and chitosan were effective on L. innocua, but had limited effect on E. coli. On the other hand, the PL-containing zein films showed good antimicrobial activity on both E. coli and L. innocua as well as on S. aureus. PL-Na 2EDTA combination also gave zein films effective on S. Typhimurium. The incorporation of PL alone or PL-Na 2EDTA combination did not cause any significant change in mechanical properties of zein films. Zein has a good potential to develop novel antimicrobial packaging materials incorporated with PL.

In this study, antioxidant activities of water-soluble protein extracts from chickpeas and white beans were investigated. The area under the curve (AUC) values of lyophilized crude protein extracts (dialyzed or undialyzed) from thermally processed (121 °C for 20 min) or heat-treated (90 °C for 20 min) chickpeas (73-91 μmol trolox/g) and white beans (39-67 μmol trolox/g) indicated a higher free radical-scavenging capacity and thermostability for chickpea proteins than for white bean proteins. The thermal processing also increased the Fe+2-chelating capacity of lyophilized chickpea crude protein extracts 1.8-fold whereas it caused a 2.3-fold reduction in the Fe+2-chelating capacity of lyophilized white bean crude protein extracts. Dialysis increased the protein content of lyophilized chickpea extracts 1.5-2-fold but it did not affect the protein content of lyophilized white bean extracts significantly. Ammonium sulfate precipitation was not effective for selective precipitation of antioxidant proteins. However, it improved the free radical-scavenging capacity of lyophilized protein extracts from thermally processed chickpeas and white beans by almost 25% and 100%, respectively. DEAE-cellulose chromatography, indicated the presence of five (A1-A5) and three (B1-B3) antioxidant protein fractions in heat-treated and thermally processed chickpea protein extracts, respectively, and can be used for the partial purification of antioxidant proteins. The results of this study showed the good potential of chickpea proteins as thermostable natural food antioxidants., İzmir Institute of Technology (Project #2004 İYTE 05) and TÜBİTAK (MİSAG # 221)

Pectin methylesterase (PME) causes considerable softening in intermediate-moisture (IM) figs rehydrated at 30 °C and cold stored at 28% to 29% moisture content Rehydration of figs at 80 °C for 16 min inactivated PME partially (25-30%), but this did not prevent the softening over 3 mo of cold storage. Also, heating did not reduce the microbial load of figs significantly and increased their browning. In contrast, rehydration of figs 1st in 2.5% H 2 O 2 at 80 °C for 8 min and then in water at 80 °C for 8 min reduced the microbial load of IM figs significantly, turned their brown color to yellow-light brown, and maintained their desired textural properties. The residual H 2 O 2 in IM figs decomposed in 3 or 1.5 wk by the in situ catalase or by application of the iron (II) sulfate-ascorbic acid residue elimination method, respectively. Hot rehydration did not affect the antioxidant activity of IM figs, but treatment of figs with H 2 O 2 increased their antioxidant activity slightly. These results indicate that the hot rehydration of figs in the presence of H 2 O 2 and cold storage may be applied to obtain safe and SO 2 -free light-colored IM fig products.