Agricultural and Food Engineering Department

Onion slices were dried in a single layer of thickness varying from 1 to 5mm in the temperature range of 50–70°C in a laboratory scale vacuum dryer. The effect of pretreatment, drying temperature and slice thickness on the drying kinetics of onion slices was studied. Four thin layer drying models namely Lewis model, logarithmic model, Page model and Fick's law

Onion (Allium cepa), a very commonly used vegetable, ranks third in the world production of major vegetables. Apart from imparting a delicious taste and flavour due to its pungency in many culinary preparations, it serves several medicinal purposes also. Processing and preservation of onion by suitable means is a major thrust area since a long time. The various kinds of treatments followed for dehydration of onion such as convective air drying, solar drying, fluidized bed drying, vacuum microwave drying, infrared drying and osmotic drying are reviewed here. These techniques are mainly used for preservation and value addition of onion. Several researchers have tried for decades to model the drying kinetics and quality parameters, which are also compiled here briefly. Keywords Onion. Dehydration. Nutritional value. Mathematical modeling Nomenclature a, b Empirical constants for equation (4.10) a w Water activity of product A x Exchange area (m 2) C, Y Optical index C' Thiosulphinate concentration (μmol/g) c 1, c 2, c 3, c 4 Model parameter values for equation (4.11) d 1, d 2, d 3, d 4 Model parameter constants for equation (4.13) db Dry basis (g/g solid) d p Dry matter fraction Greek α Water content ratio X/X 0 α 0, α 1 , α 2, α 3 Empirical constants for equation (4.4) β 0, β 1 , β 2, β 3, β 4 Empirical constants for equation (4.6) δ 0, δ 1 , δ 2, δ 3, δ 4 Empirical constants for equation (4.7) γ 0, γ 1 , γ 2, γ 3 Empirical constants for equation (4.5) η 0, η 1 , η 2, η 3, η 4 Empirical constants for equation (4.2

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Okra, Abelmoschus esculentus L. (Moench) is an important vegetable crop cultivated in tropical, subtropical and warm temperate regions around the world. Besides the nutritional benefit, the different parts of the plant are used extensively in traditional medicine (antidiabetic, antipyretic, diuretic, antispasmodic, etc) around the world. This review critically assesses the nutritional values, phytochemistry, preclinical pharmacological properties and the possible future application of the okra. Effort is made to correlate the traditional claims in the context of experimental evidences.

Onion slices were dehydrated under vacuum to produce good quality dried ready-to-use onion slices. Colour development due to non-enzymatic browning and flavour loss in terms of thiosulphinate concentration was determined, along with moisture content and rehydration ratio. Kinetics of non-enzymatic browning and thiosulphinate loss during drying was analysed. Colour change due to non-enzymatic browning was found to be much lower in the case of vacuum dried onion, and improved flavour retention was observed as compared to hot air dried onion slices. The optical index values for non-enzymatic browning varied from 18.41 to 38.68 for untreated onion slices and from 16.73 to 36.51 for treated slices, whereas thiosulphinate concentration in the case of untreated onion slices was within the range of 2.96-3.92 μmol g

Assessment of various quality parameters of vacuum dried onion, with or without pretreatment was attempted. Colour, flavor and rehydration ratio were analyzed and compared with those of convective air drying. Tissue microstructure images of dehydrated onion were studied and compared with convective air drying and microwave drying, with the help of scanning electron microscopy. The texture of dried onion was measured in terms of hardness, cohesiveness, springiness, gumminess and chewiness using texture analyzer. All these parameters were higher in case of treated samples compared to untreated ones. True density and thermal conductivity of vacuum dried onion were assessed with the changing moisture content. Colour, flavor and microstructure of vacuum dried onion were better than convective air drying. True density was found less compared to hot air dried product however thermal conductivity was almost comparable. The vacuum drying method for onion was found suitable over convective air drying which is normally practiced commercially. Keywords Onion Á Vacuum drying Á Texture Á Microstructure Á Colour Á Flavour Á Density Á Thermal conductivity List of symbols % Percentage°C Degree Celsius A Absorbance ADOGA American Dehydrated Onion and Ginger Association b Cell path length, cm db Dry basis, kg water kg dry solid-1 K Degree Kelvin k Thermal conductivity of vacuum dried onion kV Kilo Volt m Wet basis moisture content of onion sample, kg water kg matter-1 min Minutes mm Millimeter N Newton, unit of force, kg m s-2 NEB Non-enzymatic browning OI Optical index R 2 Coefficients of determination q t Bulk density of vacuum dried onion, kg m-3 SE Standard error SEM Scanning electron microscopy TC Thiosulphinate concentration of the solution, lmol g-1 TPA Texture profile analysis W Watt wb Wet basis, kg water kg total matter-1 e Molar absorptivity of thiolsulphinate solution at 254 nm, g/(lmol cm)

Dehydration of untreated and pre-treated onion slices under vacuum was optimised using the response surface methodology. The effects of the drying temperature (50–70°C), slice thickness (1–5 mm), and treatment (5% NaCl and 0.2% K<sub>2</sub>S<sub>2</sub>O<sub>5</sub>) were observed on the responses, viz. final moisture content, colour change, flavour content, and rehydration ratio of the dehydrated onion slices. Full factorial design was employed for the analysis. Optimisation of the vacuum drying process was achieved based on the criteria of maximum flavour retention, 3–3.5% db moisture content, acceptable colour, and rehydration ratio using numerical technique. The optimum condition for the treated sample was found at 58.66°C drying temperature and 4.95 mm slice thickness. Optimum values of the response parameters, namely the moisture content, colour, flavour content, and rehydration ratio were obtained as 3.5% d.b., 30...

Bacterial infections are raising serious concern across the globe. The effectiveness of conventional antibiotics is decreasing due to the global emergence of multi-drug-resistant (MDR) bacterial pathogens, caused by their indiscriminate and inappropriate use in infected patients and the food industry. New classes of antibiotics with different actions against MDR pathogens need to be developed urgently. This article focuses on several ways and future directions to search for the next generation of safe and effective antimicrobial compounds, like antimicrobial peptides, phage therapy, phytochemicals, metalloantibiotics, LPS and efflux pump inhibitors to control the infections caused by MDR pathogens.

Bacterial infections are raising serious concern across the globe. The effectiveness of conventional antibiotics is decreasing due to the global emergence of multi-drug-resistant (MDR) bacterial pathogens, caused by their indiscriminate and inappropriate use in infected patients and the food industry. New classes of antibiotics with different actions against MDR pathogens need to be developed urgently. This article focuses on several ways and future directions to search for the next generation of safe and effective antimicrobial compounds, like antimicrobial peptides, phage therapy, phytochemicals, metalloantibiotics, LPS and efflux pump inhibitors to control the infections caused by MDR pathogens.

We previously isolated Streptomyces racemochromogenes strain 10-3, which produces a phospholipase D (PLD) with high transphosphatidylation activity. Here, we purified and cloned the PLD (PLD103) from the strain. PLD103 exerted the highest hydrolytic activity at a slightly alkaline pH, which is in contrast to the majority of known Streptomyces PLDs that have a slightly acidic optimum pH. PLD103 shares only 71-76% amino acid sequence identity with other Streptomyces PLDs that have a slightly acidic optimum pH; thus, the diversity in the primary structure might explain the discrepancy observed in the optimum pH. The purified PLD displayed high transphosphatidylation activity in the presence of glycerol, L-serine, and 2-aminoethanol hydrochloride with a conversion rate of 82-97% in a simple one-phase system, which was comparable to the rate of other Streptomyces PLDs in a complicated biphasic system.

Microbial infections originating from medical care facilities are raising serious concerns across the globe. Therefore, nanotechnology-derived nanostructures have been investigated and explored due to their promising characteristics. In view of this, silver-based antimicrobial hydrogels as an alternative to antibioticbased creams could play a crucial role in combating such infections. Toward this goal, we report a simple method for the synthesis and assembly of silver nanoparticles in a biopolymer physical gel derived from Abroma augusta plant in imparting antimicrobial properties against nosocomial pathogens. Synthesized silver nanoparticles (diameter, 30 ± 10 nm) were uniformly distributed inside the hydrogel. Such synthesized hydrogel assembly of silver nanoparticles dispersed in the biopolymer matrix exhibited hemocompatibility and antimicrobial and antibiofilm characteristics against nosocomial pathogens. The developed hydrogel as a surface coating offers reduced hardness and modulus value, thereby minimizing the brittleness tendency of the gel in the dried state. Hence, we believe that the hierarchical assembly of our hydrogel owing to its functional activity, host toxicity, and stability could possibly be used as an antimicrobial ointment for bacterial infection control.

The objective of the present investigation deals with optimization of L-lactic acid production from Zizyphus
oenophlia, a potential low cost substrate. Central composite design (CCD) based on response surface
methodology (RSM) was employed as a statistical tool to investigate the effect of substrate: media ratio,
temperature, pH and inoculum volume on lactic acid production. Under optimum condition, the experimental
yield was 95.09%, which matched well with the predictive yield of 95.45%. HPLC and circular
dichroism (CD) analysis of the fermented product was carried out to confirm the presence of lactic acid
in its L (+) seriospecificity respectively. For application of lactic acid in biotechnological sector polymerization
studies were carried out. The PLA upon recovery through direct polycondensation reaction
resulted in the yield of 85%.

The present study involves synthesis of polylactic
acid (PLA) using purified lactic acid from fermented broth
of Jackal jujube (Zizyphus oenophlia). A polyphenolic
compound, humic acid (HA) of biological origin was
incorporated to the PLA in order to reinforce the PLA
chain without compromising its biodegradability and biocompatibility.
Under optimized conditions of polymerization,
modified L-PLA yield improved up to 93%. The molecular
weight was found to be 6.4×105. Different physicochemical
properties of the polymer were explored for its further
application in different fields. Incorporation of intermolecular
bond between PLA and HA was confirmed by FT-IR
spectroscopy technique. Addition of HA not only reduced
the crystallinity of PLA, but also had increased flexibility
and elasticity to much greater extent. The results showed
that, apart from enhancing the physicochemical properties
of PLA, the process also had reduced the production cost
of the polymer, while mitigating the demands of
environmental protection agencies.

Now a days, polylactic acid (PLA) and its derivatives are receiving significant attention due to its
versatile applications. The present study provides a deep insight on major structural and
functional properties of novel PLA-HA polymer synthesized by incorporating humic acid (HA)
in PLA. Topographical features of both pure and modified PLA have been studied using SEM
and AFM to analyze their comparative surface microstructures. Incorporation of HA was found
to enhance slightly the thermal stability profile of the polymer. However, reduction of Tg, Tm and
degree of crystallinity has also been noticed, which in turn resulted in enhanced ductility and
higher elongation at break. Moreover, improvement in radical scavenging properties, total
available phenolics (0.075 μmole GAE/g film) and water absorption capacity (90.65%) has been
observed which essentially suggested introduction as well as enhancement of several utility
features, originally absent in pure PLA. The study thus predicts multifaceted applications of
PLA-HA polymer, from industrial packaging to fabrication of biomedical devices depending on
its superior characteristics as compared to pure PLA.