Effect of processing on quality and shelf life of leafy vegetables

There is a need to sustain quality of ready-to-eat (RTE) leafy vegetables in order to improve shelf life of the products during postharvest storage. The main objective of this thesis was to investigate the effect of compression towards the quality and shelf life of the RTE leafy vegetables. This thesis focused on spinach leaves as the representation of the RTE leafy vegetables. For this purpose, uniaxial compression was chosen as a method to induce damage to the leaves. The effects of compression towards qualities of RTE spinach were evaluated. The quality measures in this study focused on mechanical and microstructural properties, physical appearance, and fresh weight. Organic spinach was found to be the best type in resisting stress compared to Teen, Salad, and Baby spinach. Population test was developed to categorise the compressed leaves into degrees of leaf injuries known as Undamaged, Minor, Halfway, and Complete teared. Force 200N was suggested to be the minimum required to pick up differences of the leaves deteriorations before and after storage. Uncompressed spinach leaves were found to have a shelf life of 14 days. Higher degrees of leaf injuries which are Halfway and Complete teared showed obvious decay since before storage. Sensory test was also conducted to study consumers’ evaluations towards visibility of leaf damage and perceptions in buying the product. Respiration rate of the RTE spinach stored at different films was also measured using a closed system. Michaelis-Menten and exponential models were used to study the respiration rate mechanism

Effect of water absorption on the mechanical properties of cross-ply hybrid pseudo- stem banana/glass fibre reinforced polypropylene composite

The initiative to reduce the consumption of non-renewable resources increases the awareness of being green in composites. The synthetic fibres are currently substituted by natural fibres applicable in various industries such as automotive and building. In this study, the effects of water absorption on the tensile and flexural properties of cross-ply hybrid pseudo-stem banana/glass fibre reinforced polypropylene composites are investigated. The hybrid banana (B)/glass(G) polypropylene composites and the reference specimens of the non-hybrid composites of the plain banana and glass fibres termed the BBB and GGG specimens were fabricated using hot compression moulding method. Water absorption test was conducted according to ASTM D570 until the specimens reached saturation. Tensile (ASTM D3039) and flexural (ASTM D790)test were carried out on the dry specimens as well as the wetted specimens. It can be observed that non-hybrid GGG has the best water absorption properties and hybrid specimen with glass as outermost skin shows a comparable result. However, water absorption reduced the mechanical properties of the composites. The incorporation of glass fibre in the composites improved overall properties of the composites. The hybrid GBG dry specimen tensile strength and wet specimen flexural strength is 136.28 and 73.86 MPa respectively. The hybrid composite GBG shows comparable flexural properties to GGG composit

Optimizing the processing factor and formulation of oat-based cookie dough for enhancement in stickiness and moisture content using response surface methodology and superimposition

Despite the utilization of dusting flour and oil to reduce dough stickiness during the production process in food industry, they do not effectively help in eliminating the problem. Stickiness remains the bane of the production of bakery and confectionery products, including cookies. In addition, the high moisture content of cookie dough is unduly important to obtain a high breaking and compression strengths (cookies with high breaking tolerance). This study was conducted in light of insufficient research hitherto undertaken on the utilization of response surface methodology and superimposition to enhance the stickiness and moisture content of quick oat-based cookie dough. The study aims at optimizating, validating and superimposing the best combination of factors, to produce the lowest stickiness and highest moisture content in cookie dough. In addition, the effect of flour content and resting time on the stickiness and moisture content of cookie dough was also investigated, and microstructure analysis conducted. The central composite design (CCD) technique was employed and 39 runs were generated by CCD based on two factors with five levels, which comprised flour content (50, 55, 60, 65, and 70%), resting time (10, 20, 30, 40, and 50 min) and three replications. Results from ANOVA showed that all factors were statistically significant at p < 0.05. Flour content between 56% and 62%, and resting time within 27 and 50 min, resulted in dough with high stickiness. High-region moisture content was observed for flour content between 60% and 70%, and within 10 and 15 min of resting time. The optimized values for flour content (V1) = 67% and resting time (V2) = 10 min. The predicted model (regression coefficient model) was found to be accurate in predicting the optimum value of factors. The experimental validation showed the average relative deviation for stickiness and moisture content was 8.54% and 1.44%, respectively. The superimposition of the contour plots was successfully developed to identify the optimum region for the lowest stickiness and highest moisture content which were at 67–70% flour content and 10–15 min resting time

Staging of larval polypedates Otilophus (Anura: Rhacophoridae)

The staging of larvae is important to understand the natural history of anuran amphibians, as it undergoes dramatic changes in morphological form. A large tree frog, Polypedates otilophus is staged for its larval development. A total of 13 individual tadpoles and two clutches of foam nests of P. otilophus were collected from the Frog Pond of Kubah National Park. The larval development is recorded starting from Stage 26 until complete metamorphosis. The information of changes in morphological features; limb development and tail resorption, and time taken (in days) are recorded. Polypedates otilophus took 94 to 108 days to complete metamorphosis, starting from the day of hatching. Gosner (1960) standardised staging table is referred in documenting the metamorphosis of Polypedates otilophus

Fenton degradation of linear alkylbenzene sulphonates (LAS)

Among Advanced Oxidation Processes (AOPs), Fenton's reagent has been efficiently used as a chemical process for wastewater treatment. Fenton's reagent is used to treat a variety of industrial wastes containing a range of toxic organic compounds. Fenton system consists of ferrous salts combined with hydrogen peroxide under acidic condition. The effect of Fenton degradation of linear alkylbenzene sulphonates (LAS) at different initial concentration (0.1x10(-3) mol/L, 0.25 x10(-3) mol/L and 0.5x10(-3) mol/L) was investigated. All experiments used a temperature of 30°C, stirring speed of 125 rpm, a reaction time of 90 min and initial pH of 3.0. It was found that 82%, 64% and 49% of TOC removals were achieved at 0.1x10(-3) mol/L, 0.25x10(-3) mol/L and 0.5x 10(-3) mol/L respectively. It was also found that the main degradation of LAS proceeds via reaction with OH• radicals. The addition of sodium benzoate, an OH• radical scavenger was inhibited and retarded the oxidation. For instance, 28 % and 82 % of TOC removals were achieved in the presence and absence of radical scavenger at LAS concentration of 0.25x 10(-3) mol/L

Effect of compression on mechanical properties of ready-to-eat (RTE) spinach varieties

Compression-induced injury is frequently encountered during handling, packaging, transporting, and storage. In this study, compression test was performed using a mechanical tester, Universal Testing Machine Z030 (Zwick/Roell, Germany). Spinach varieties (Teen, Organic, Salad, and Baby) were used to study the response of spinach varieties towards stress. For single loading/unloading compression, maximum work (MaxW) and area under the curve (AUC) required to compress Organic spinach were found to be the highest followed by Teen and Salad spinach. The MaxW and AUC were found to be decreasing after storage which showed that the total work generated to compress the leaves was reduced due to texture degradation of the product after storage. For multiple loading/unloading compression, as the number of compressions increased, the MaxW decreased. Similar trend was observed at day 6. Apart from that, the MaxW for all the three spinach types were found to be similar at the 5th compression. This shows that regardless of the spinach types, they reached maximum resistance towards stress after the 5th consecutive compression. Under 200 N compression, leaves with stem required higher energy to compress compared to leaves without stem. However, for leaves compressed under 50 N and 100 N, the difference was only noticed on the 1st compression. The MaxW was found to be similar for leaves with stem and without stem starting from the 2nd compression till the 5th compression. The irregular and larger cell size of Organic spinach as compared to round-shaped and smaller cell size of Teen and Salad spinach may contribute to the ability of the Organic spinach tissue to have higher resistance towards mechanical stress during compression

Corn starch/chitosan nanoparticles/thymol bio-nanocomposite films for potential food packaging applications

This work aims to develop corn starch/chitosan nanoparticles/thymol (CS/CNP/Thy) bio-nanocomposite films as potential food packaging materials that can enhance the shelf life of food. CS/CNP/Thy bio-nanocomposite films were prepared by the addition of different concentrations of thymol (0, 1.5, 3.0, 4.5 w/w%) using a solvent casting method. The resulting films were characterized in terms of optical, mechanical, and water vapor permeability (WVP) properties. The addition of thymol was found to reduce the tensile strength (TS), elongation at break (EAB), and Young’s modulus (YM) of the films. Generally, the increment in the concentration of thymol did not significantly affect the TS, EAB, and YM values. The addition of 1.5 w/w% thymol increased the WVP of the films but the WVP reduced with the increase in thymol concentrations. CS/CNP/Thy-3% bio-nanocomposite films demonstrated the potential to lengthen the shelf life of cherry tomatoes packed with the films, whereby the cherry tomatoes exhibited no significant changes in firmness and the lowest weight loss. In addition, no mold growth was observed on the sliced cherry tomatoes that were in direct contact with the films during 7 days of storage, proving the promising application of the films as active food packaging materials

Some engineering properties of pineapple fruit

Pineapple is a tropical fruit that is highly relished for its unique aroma and sweet taste. In contrast to other tropical fruits, pineapples typically feature medium-sized fruits with yellow flesh. Based on the physical properties of pineapple fruit variety MD2 such as dimensions, geometric mean diameter (Dg), arithmetic mean diameter arithmetic mean diameter (Da), surface area, volume, sphericity, aspect ratio, and projected area and the best-fit mass models have been determined. From the result obtained, the physical properties such as length, thickness, width, Dg, Da and circumference were found to be 217.8mm, 132.7mm, 132.9mm, 156.5mm, 161.2mm, 394.3mm respectively. Meanwhile for the aspect ratio, mass, volume surface area, sphericity and projected area perpendicular to dimension namely PAL, PAT, AND PAW were found to be 0.61, 1730.4g, 1420 cm3, 77107.4 mm2, 0.72, 22746.0 mm2, 13942.9 mm2, and 16866.3 mm2 respectively. For all physical properties except volume, the best fit mass model to predict mass of pineapple fruits was the quadratic model. Additionally, the findings demonstrated that, in comparison to other attributes, the mass model based on actual volume was more appropriate, with the highest determination coefficient (R2) for Quadratic and S-curve model. For developing and optimizing machinery for handling, maintenance, distribution, and storage, the mass model of pineapple fruits according to the actual volume in the outcomes is relatively important

Effect of synthesis temperature on the size of ZnO nanoparticles derived from pineapple peel extract and antibacterial activity of ZnO–starch nanocomposite films

This research investigated the effect of synthesis temperature on the size and shape of zinc oxide (ZnO) nanoparticles (NPs) synthesized using pineapple peel waste and antibacterial activity of ZnO NPs in starch films. Zinc oxide NPs synthesized at different temperatures were characterized by Fourier transform infrared spectroscopy, X-ray diffraction analysis, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Micrographs of ZnO NPs synthesized at 28 and 60 °C showed that synthesis temperature affected the sizes and shapes of ZnO NPs. The non-heated (28 °C) condition resulted in NPs with diameters in the range of 8–45 nm with a mixture of spherical and rod shapes, whereas the heated (60 °C) condition led to NPs with diameters in the range of 73–123 nm with flower rod shapes. The ZnO–starch nanocomposite films incorporated with 1, 3, and 5 wt.% ZnO NPs were prepared via a film casting method. The antibacterial activity of the films against Gram-positive and Gram-negative bacteria was investigated using the disc diffusion method. The results showed an increase in the inhibition zone for Gram-positive bacteria, particularly Bacillus subtilis, when the concentration of ZnO NPs incorporated in the film was increased from 1 to 5 wt.%

Characterization of active sweet potato-based films containing thymol at different varieties: VitAto and Anggun

Sweet potato starch (SPS) films from local Malaysia varieties particularly, VitAto (orange-fleshed) and Anggun (purple-fleshed) were developed to characterize the physical, mechanical, thermal, and antimicrobial properties. The SPS films were fabricated by solvent casting technique, incorporating different types and concentrations of plasticizer including sorbitol (S) and glycerol (G) at 0, 15, and 30 % of starch. The VitAto SPS films exhibited higher brightness and lower solubility in water than the Anggun SPS films. The plasticized SPS films with 15 % plasticizer demonstrated better tensile strength (TS) and elongation at break (EaB) than the films containing 30 % plasticizer. For the plasticized VitAto SPS films at 15 % loading, the glycerol and sorbitol-plasticized films demonstrated better mechanical and thermal properties than the plasticized Anggun SPS films. The addition of 5 % thymol into SPS films increased the film solubility in water and improved the EaB, while the TS was reduced remarkably. Functional chemical analysis confirmed the presence of intermolecular interaction between the film’s components. The SPS films with thymol showed positive inhibition against Staphylococcus aureus and Escherichia coli in liquid media. Qualitative observations revealed that the active SPS films was able to reduce the growth of fungal on cherry tomato samples and retained the firmness of the food sample. The active SPS films have the potential to be used in food packaging in order to prolong the shelf life of perishable food products