Volume 13, Issue 1 -

Food drying is one of the important methods to prevent microbial growth during preservation. However, it is a complex non-linear process where the quality of the food depends on environmental conditions. Therefore, food drying must be carried out under controlled environment. In this paper, an internal model control (IMC) scheme is developed for pineapple drying using the evolutionary algorithms namely: genetic algorithm (GA) and particle swarm optimization (PSO) to achieve the desired quality (single objective). In order to reduce the control effort and hence the cost, without compromising the desired quality, a multi-objective control scheme is also formulated using weighted sum method. The closed loop performance of the control scheme for GA-based IMC-PI controller and PSO-based IMC-PI controller are analyzed for servo and regulatory operations. The results thus obtained are compared both qualitatively and quantitatively. From the simulation results it is observed that PSO-based IMC-PI controller gives better performance and better range of the temperature compared to the other control schemes.

Abstract: Fucoxanthin intake has been correlated with the functions of anti-obesity and anti-oxidation, but applications of it in functional food or dietary supplements are still challenging due to its poor water-solubility, chemical instability, and low bioavailability. In this work, to study physicochemical and biological properties of fucoxanthin nanoemulsions, we investigated the influence of emulsion particle diameter on the stability of fucoxanthin during storage time and bioaccessibility in-vitro digestion. The structured lipid that enriched pinolenic acid at sn-2 position was chosen as the oil phase and the fucoxanthin oil-in-water nanoemulsions with droplet diameters of 344, 173, and 98 nm were prepared through a high-pressure microfluidizer. Then fucoxanthin emulsions were stored for 28 days at 4, 37, and 55 °C. Results showed that the physical stabilities of droplets were decreased with increases in the initial size and storage temperature, while the change of fucoxanthin retention indicated that fucoxanthin chemical stability was improved with increasing emulsion particle size. The augmentation of lipolysis and the value of free fatty acids (FFA) released in vitro digestion proved that digestion stability of fucoxanthin emulsion reduced with decreasing initial particle diameter, which was probably attributed to the increased surface area interacting with pancreatic lipase with decreasing droplet size. In addition, the concentrations of fucoxanthin in micelle phase were appreciable increased as droplet size decreased. Therefore, the bioaccessibility of fucoxanthin was improved. These results may benefit the optimization of an emulsion-based delivery system for fucoxanthin in food applications.

The physicochemical characteristics and the activity of the polyphenol oxidase from piñuela fruit juices were determined at two ripening stages. The antioxidant capacity was evaluated by the superoxide anion yield. The ripening stage showed greater ability to inhibit (O2.−$O_2^{. -}$, 35.3 %). The inhibition of superoxide dismutase was higher for both ripe (88.29 %) and unripe (95.94 %) states. The rheological behaviour of the juice was satisfactorily described using Herschel-Bulkley model (R 2 > 0.99). The concentration effect on the rheological parameters was described by the potential law model, and the temperature effect on the viscosity was described based on the Arrhenius equation, finding activation energy values from 11.94 and 17.80 kJ/mol. These results make Bromelia karatas L. a promissory fruit due to their content of secondary metabolites and its antioxidant activity, which could be associated to the presence of phenolic compounds, specifically flavonoids. Variations in these metabolites could also account for structural changes, physicochemical properties, the integrity protection of the fruit against adverse and an alternative to food products.

A series of experiments on the heat and mass transfer of millet particles are conducted in order to demonstrate the effects on drying characteristics of particles in this work. Experimental results illustrate that thermal conductivity between particles is significantly influenced by temperature and moisture content of millet particles. The temperature of particles in axial and radial direction increases because of the increase of inner wall temperature and decreases with the increase of air flow velocity. Moreover, the moisture content of particles near the inner wall has experienced a significant drop with the increase of inner wall temperature. As a consequence, the increase of air flow velocity results from the decrease of particles moisture content and drying rate of particles increases due to the increase of air flow velocity. Furthermore, the accumulated height of particles has barely influenced on the drying characteristics of millet particles.

Abstract: The effects of deproteinization and drying methods on the antioxidant activities and physiochemical properties of C. militaris polysaccharide were evaluated. The results showed that the IC50 of crude polysaccharide (CMP)was similar with that of deproteined polysaccharide by sevag (CMP-D-S), but significant higher ( p  < 0.05)than that of deprotiened polysaccharie by enzyme (CMP-D-E)on DPPH· scavenging. The IC50 of CMP was significant higher ( p  < 0.05)than that of CMP-D-S and CMP-D-E on OH· scavenging. Deproteinization by sevag or enzymatic method could not improve the antioxidant activity of C. militaris polysaccharide. However, drying methods influenced the antioxidant activities of C. militaris polysaccharide. Polysaccharide dried by freeze drying (CMP-F)showed respectively 55.47 % and 61.99 % higher OH· scavenging capacity on IC50 than that dried by hot air drying (CMP-H)and spray drying (CMP-S). The IC50 of CMP-F was 56.23 % higher than that of CMP-S, but similar with that of CMP-H on ABTS· scavenging. The reducing power of CMP-F was respectively 20.10 % and 27.25 % higher than that of CMP-H and CMP-S at 6 mg/mL. Spectroscopy analysis showed the dried CMPs were similar in IR and UV absorption. However, the monosaccharide ratio of CMP was changed by drying techniques. Morphological analysis showed that CMP-F consisted mainly of fluffy powder with rough and porous surface, CMP-S was spherical particle with smooth surface, and CMP-H was pyknotic and similar to anomalistic stones. Freeze drying was a recommendable method for antioxidant polysaccharide preparation from C. militaris .

Polysaccharides from Cordyceps militaris show multiple biological activities, such as antioxidation, antitumor, antivirus and immunomodulating properties, etc. The nutritional requirements for antioxidant polysaccharide bio-synthesis by submerged culture of C. militaris were evaluated on the basis of assay for DPPH radical scavenging ability and reducing power in this work. The results showed the best antioxidant activity of polysaccharide could be achieved when the media consisted of mannose, peptone, MgSO 4 , Na 2 HPO 4 , and KH 2 PO 4 . Furthermore, the main fraction of antioxidant polysaccharide, CMP-2, was preliminary isolated from the fermentation broth of C. militaris by ethanol precipitation, filtration, and DEAE cellulose-52 chromatography. CMP-2 was composed of mannose, rhamnose, glucose and galactose in a ratio of 2527:164:172:100, and had an average molecular weight (Mw) of approximately 8175 Da. The results suggested antioxidant polysaccharide could be produced by submerged culture of C. militaris and the medium composition significantly affected its DPPH radical scavenging ability and reducing power.

Abstract: Peroxidase isolated from custard apple ( Annona squamosa L .) being a heat stable enzyme can be inactivated by heat processing and ultrasonication treatment as well. Heat processing took up to 22 min at 91 °C for complete inactivation of peroxidase. The ultrasonication treatment was performed at 40, 55, 70, 85 and 100 W ultrasonic power and was found to achieve complete inactivation at 85 W as well as at 100 W power within 5 min. The heat inactivation followed first-order reaction kinetics and the activation energy ( E a ) calculated from Arrhenius plot was found to be 7.03 × 10 4 J/mol, which was near the reported range for peroxidases. Heat processing caused 52.7 % loss of vitamin C while achieving complete inactivation of peroxidase at 91 °C for 22 min, whereas ultrasonication caused 21.6 % vitamin C loss at 85 W power within 5 min. Ultrasonication was thus found to be efficient in retaining vitamin C while achieving complete enzyme inactivation.

Response surface methodology (RSM) was adopted to investigate the optimum operation conditions to develop the biodegradable pellet and to analyze the effects of extrusion processing variables, including tapioca starch content (30–50 %), xylitol content (45–75 g) and barrel temperature (140–170 °C) on characteristics of the Poly (hydroxybutyrate-co-hydroxyvalerate) (PHBV)-starch composites. Maximum loading and maximum displacement of composites could be improved with a deliberate amount of xylitol as well as with rising barrel temperature. The water absorption reduced by addition of xylitol in comparison to increasing tapioca starch content. Coefficients of determination were higher than 0.85 of the response variables and significant regression models were applied to RSM optimization. Based on the response surface and superimposed plots, the compromised optimization condition obtained by numerical optimization was 39.04 % of tapioca-starch content, 56.99 g of xylitol content and 156.58 °C of barrel temperature.

Total phenolic content, total flavonoid content, antioxidant activity and individual phenolic compounds were assessed in full fat and defatted walnut kernel. For quantification of phenolic fraction of walnut kernels, two different solvents (methanol and ethanol) and two methods of extraction (ultrasonic-assisted extraction and Soxhlet extraction) were tested. Total phenolics, flavonoid content and antioxidant capacity of alcoholic extracts varied depending on the solvent used and extraction methods. Seventeen phenolic compounds were detected and the study provides evidence on high phenolic contents and high antioxidant potential of full fat walnut kernel and defatted walnut kernel. The Soxhlet extraction is the best in terms of the amounts of total phenolic content (2,089.2 mg gallic acid equivalent/100 g dry matter), while the ultrasonic assisted extraction is a fast method but resulted in significantly lower phenolic content (667.3–1,426.8 mg gallic acid equivalent /100 g dry matter). The concentrations of phenolics (especially (+)-catechin hydrate, juglone, vanillic acid, caffeic acid, ferulic acid, sinapic acid, salicylic acid and ellagic acid) are many fold lower in ultrasonic-assisted extraction as compare to the Soxhlet method using the same extraction solvent. The results of this study provide evidence on high phenolic contents and high antioxidant potential of full fat and defatted walnut kernel.

Response surface methodology was used to optimize the spray-drying process for the development of stingless bee honey powder. The independent variables were: inlet air temperature (110–150  o C) and maltodextrin 10DE content (50–70 % wb). The responses were powder yield, moisture, volatiles retention, solubility time, hygroscopicity, bulk loose, and hydroxymethylfurfural content. Powder moisture content, solubility time, hygroscopicity and loose bulk density were negatively affected by inlet air temperature, while powder yield, volatiles retention and hydroxymethylfurfural content were directly related. Powder yield, volatiles retention and solubility time increased with the rise in maltodextrin content, while moisture content, hygroscopicity, loose bulk density and hydroxymethylfurfural content were negatively affected by maltodextrin content. Multiple response optimization indicated that an inlet air temperature of 150  o C and maltodextrin content of 61 % wb were predicted to provide 40 % powder yield, 4.9 % wb moisture content, 71 % volatiles retention, 242 s solubility time and 232 mg/kg hydroxymethylfurfural content.