Physico-chemical properties of flour and starch from jackfruit seeds (Artocarpus heterophyllus Lam.) compared with modified starches

Jackfruit (Artocarpus heterophyllus Lam.) is one of the most popular tropical fruits grown in Asia. The objective of this study was to compare physico‐chemical properties of native flour and starch from jackfruit seeds (A. heterophyllus) to commercially modified starches (Novation 2300 and Purity 4). The colour of jackfruit seed starch was lighter than the Novation 2300 starch but darker than the Purity 4 starch. The jackfruit seed starch had a narrower gelatinization temperature range than Purity 4 and required less gelatinization energy compared with modified starches. The peak viscosity of jackfruit seed starch was lower than commercially modified starches. Likewise, setback viscosity, swelling power and solubility of jackfruit seed starch showed similar trends. Results from this study suggest that native starch from jackfruit seed could be used as an alternative for modified starches in a system needing starch with a high thermal and/or mechanical shear stability.     

Physicochemical properties of pectins from okra (Abelmoschus esculentus (L.) Moench)

Okra pectin obtained by hot buffer extraction (HBSS) consists of an unusual pectic rhamnogalacturonan I structure in which acetyl groups and alpha galactose residues are substituted on rhamnose residues within the backbone. The okra Chelating agent Soluble Solids (CHSS) pectin consists of slightly different structures since relatively more homogalacturonan is present within the macromolecule and the rhamnogalacturonan I segments carry slightly longer side chains. The rheological properties of both okra pectins were examined under various conditions in order to understand the unusual slimy behaviour of okra pectins. The viscosity of the okra HBSS pectin was 5–8 times higher than the viscosity of the okra CHSS pectin. The okra HBSS pectin showed an elastic behaviour (G′ > G″) over a wide range of frequencies (10⁻¹–10 Hz), at a strain of 10%, while okra CHSS and saponified okra HBSS/CHSS pectin showed predominantly viscous responses (G′ < G″) over the same frequency range. The results suggest that the structural variation within the okra pectins greatly affect their rheological behaviour and it is suggested that acetylation of the pectin plays an important role through hydrophobic associations. Dynamic light scattering was used to study the association behaviour of both okra pectins at low concentration (0.001–0.1% w/w). Results showed that the saponified okra pectins did not exhibit a tendency to aggregate in the concentration range studied, whereas both non saponified samples showed a substantial degree of association. These results suggest that the unusual slimy behaviour of the non saponified samples may be related to the tendency of these pectins to associate, driven by hydrophobic interactions.     

Effect of Okra Cell Wall and Polysaccharide on Physical Properties and Stability of Ice Cream

Stabilizers are used in ice cream to increase mix viscosity, promote smooth texture, and improve frozen stability. In this study, the effects of varying concentrations (0.00%, 0.15%, 0.30%, and 0.45%) of okra cell wall (OKW) and its corresponding water‐soluble polysaccharide (OKP) on the physical characteristics of ice cream were determined. Ice cream mix viscosity was measured as well as overrun, meltdown, and consumer acceptability. Ice recrystallization was determined after ice cream was subjected to temperature cycling in the range of ?10 to ?20 °C for 10 cycles. Mix viscosity increased significantly as the concentrations of OKW and OKP increased. The addition of either OKW or OKP at 0.15% to 0.45% significantly improved the melting resistance of ice cream. OKW and OKP at 0.15% did not affect sensory perception score for flavor, texture, and overall liking of the ice cream. OKW and OKP (0.15%) reduced ice crystal growth to 107% and 87%, respectively, as compared to 132% for the control (0.00%). Thus, our results suggested the potential use of OKW and OKP at 0.15% as a stabilizer to control ice cream quality and retard ice recrystallization. OKP, however, at 0.15% exhibited greater effect on viscosity increase and on ice recrystallization inhibition than OKW.     

Use of Average Molecular Weights for Product Categories to Predict Freezing Characteristics of Foods

ABSTRACT:  In the design of food freezing process, food property parameters, initial freezing temperature ( T_Fi ), and frozen water fraction ( X_I ) are required. The predictive approaches of these 2 parameters have been developed based on mass fractions and molecular weights of specific food components such as proteins, carbohydrates, minerals, and acids/bases. In this study, the molecular weights of the key mineral and acid/base components were successfully represented using average molecular weights (     ) and 4  T_Fi  and  X_I  calculation approaches were proposed. Based on an analysis of 212 food products, the absolute differences (AD) between the experimental and predicted  T_Fi  values for the 4 approaches were small. The prediction for the food model category was excellent with average AD (     ) values as low as ± 0.03 °C. For the other food categories, the prediction efficiency was impressive with     values between ± 0.22 and ± 0.38 °C. The predicted relationship between temperature and  X_I  for all analyzed food products provided close agreements with experimental data.     

Whey protein-okra polysaccharide fraction blend edible films: tensile properties, water vapor permeability and oxygen permeability

BACKGROUND: A hot‐buffer‐soluble‐solid fraction (HBSS) and an alkaline‐soluble‐solid fraction (ASS) of okra polysaccharides (OKP) were obtained using sequential extraction. These fractions were combined with whey protein isolate (WPI) and glycerol (Gly) plasticizer to form blend edible films. Effects of OKP fraction and content on tensile properties, water vapor permeability (WVP) and oxygen permeability (OP) were determined. RESULTS: HBSS film had significantly higher percent elongation (%E) and lower elastic modulus (EM), WVP and OP than ASS film. Increasing HBSS or ASS content in blend films with WPI significantly reduced film tensile strength and EM and increased film %E and WVP. OP values for WPI–HBSS blend films were significantly lower than OP for WPI or HBSS film. WPI–HBSS and WPI–ASS blend films had lower WVP and OP than WPI films with equivalent tensile properties. CONCLUSIONS: WPI–HBSS blend films have higher WVP and lower OP than WPI film or HBSS film, indicating unique interactions between WPI and HBSS. Compared to WPI film, WPI–HBSS blend films have improved flexibility, stretchability and oxygen barrier. Different HBSS and ASS compositions and structures are responsible for property differences between HBSS and ASS films and between WPI–HBSS and WPI–ASS blend films. Copyright © 2010 Society of Chemical Industry     

Ohmic Heating of an Electrically Conductive Food Package

Ohmic heating through an electrically conductive food package is a new approach to heat the food and its package as a whole after packing to avoid post‐process contamination and to serve consumer needs for convenience. This process has been successfully completed using polymer film integrated with an electrically conductive film to form a conductive package. Orange juice packed in the conductive package surrounded with a conductive medium was pasteurized in an ohmic heater. A mathematical model was developed to simulate the temperature distribution within the package and its surroundings. A 3‐D thermal‐electric model showed heating uniformity inside the food package while the hot zone appeared in the orange juice adjacent to the conductive film. The accuracy of the model was determined by comparing the experimental results with the simulated temperature and current drawn; the model showed good agreement between the actual and simulated results. An inoculated pack study using Escherichia coli O157:H7 indicated negative growth of viable microorganisms at the target and over target lethal process temperatures, whereas the microorganism was present in the under target temperature treatment. Consequently, our developed ohmic heating system with conductive packaging offers potential for producing safe food.     

Electrolytically exfoliated graphene–polylactide‐based bioplastic with high elastic performance

This work reports an innovative way to prepare biopolymer composite by incorporating graphene (GP) synthesized from electrolytic exfoliation into biodegradable polymer blend (polylactide/epoxidized palm oil: PLA/EPO) based on melt‐blending method and studies their physical properties for food packaging and related applications. Multilayer GP structure synthesized by electrolytic exfoliation is confirmed by transmission electron microscopy and Raman spectroscopy, whereas homogeneous GP incorporation in PLA/EPO is verified by scanning electron microscopy and X‐ray diffraction. From thermogravimetric analysis and heat deformation temperature (HDT) studies, the decomposition and HDTs of PLA/EPO/GP composites are higher than those of PLA/EPO but are lower than those of pristine PLA and tend to decrease with increasing GP content because of thermal conductivity effect. From standard tensile test, loading of GP in PLA/EPO at an optimal concentration of 0.6 wt % results in higher elongation at break by as much as 52%. The observed additional elongation under a given tension and the corresponding lower tensile strength/Young's modulus may be attributed to lower binding force of materials in the composite because of the presence of relatively weak GP–PLA/EPO interfaces. Moreover, oxygen permeability is found to decrease with increasing GP contents and oxygen permeability is reduced by 40.33% at the GP loading concentration of 0.6 wt %. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41439.