Pradeep Puligundla

Very high gravity (VHG) ethanolic brewing and fermentation: a research update.

There have been numerous developments in ethanol fermentation technology since the beginning of the new millennium as ethanol has become an immediate viable alternative to fast-depleting crude reserves as well as increasing concerns over environmental pollution. Nowadays, although most research efforts are focused on the conversion of cheap cellulosic substrates to ethanol, methods that are cost-competitive with gasoline production are still lacking. At the same time, the ethanol industry has engaged in implementing potential energy-saving, productivity and efficiency-maximizing technologies in existing production methods to become more viable. Very high gravity (VHG) fermentation is an emerging, versatile one among such technologies offering great savings in process water and energy requirements through fermentation of higher concentrations of sugar substrate and, therefore, increased final ethanol concentration in the medium. The technology also allows increased fermentation efficiency, without major alterations to existing facilities, by efficient utilization of fermentor space and elimination of known losses. This comprehensive research update on VHG technology is presented in two main sections, namely VHG brewing, wherein the effects of nutrients supplementation, yeast pitching rate, flavour compound synthesis and foam stability under increased wort gravities are discussed; and VHG bioethanol fermentation studies. In the latter section, aspects related to the role of osmoprotectants and nutrients in yeast stress reduction, substrates utilized/tested so far, including saccharide (glucose, sucrose, molasses, etc.) and starchy materials (wheat, corn, barley, oats, etc.), and mash viscosity issues in VHG bioethanol production are detailed. Thereafter, topics common to both areas such as process optimization studies, mutants and gene level studies, immobilized yeast applications, temperature effect, reserve carbohydrates profile in yeast, and economic aspects are discussed and future prospects are summarized.

Proof-of-concept study of chitosan-based carbon dioxide indicator for food packaging applications.

A chitosan-based carbon dioxide (CO(2)) indicator was developed to monitor freshness or quality of packaged foods during their storage, as elevated CO(2) levels inside a package is one of the prime indicators of microbial spoilage of food. The objective of this proof-of-concept study, therefore, was to develop a chitosan-based CO(2) indicator and to investigate its performance in different operating environments. For the enhancement of signal strength of indicator, 2-amino-2-methyl-1-propanol (AMP) was used as an additive to the chitosan solution. Aqueous chitosan-AMP suspensions were prepared by addition of chitosan (0.1%, 0.2% and 0.4%) and AMP (0%, 5%, 10% and 20%) to distilled water at pH 7.0. Thereafter, the aqueous chitosan suspensions were incubated under 100% and 20% CO(2) test atmospheres. The aqueous solubility of chitosan, which in turn impacts the degree of transparency of the suspension, was tested at different pHs and time intervals, spectrometrically. The transparency of 0.2% chitosan aqueous suspension increased dramatically below pH 6.5 under 20% or 100% CO(2) incubation. The addition of a 5% AMP concentration to the chitosan suspension was found optimal for maximum CO(2) absorption and this, therefore, increased transparency by more than 90%.

Potentials of Microwave Heating Technology for Select Food Processing Applications - a Brief Overview and Update

In recent years, microwave heating has been increasingly popular all over the world, in particular for modern household food-processing applications, due to increased economic merits in many developing countries such as steady economic growth, high disposable income, etc. This trend also seems to be associated with increased awareness about the benefits of nutritious and healthy foods as well as functionalities of certain phytochemicals in diets, which may act as neutraceuticals. Microwave heating is known for its operational safety and nutrient retention capacity with minimal loss of heat-labile nutrients such as B and C vitamins, dietary antioxidant phenols and carotenoids. This review was aimed to provide a brief yet comprehensive update on prospects of microwave heating for food processing applications, with special emphasis on the benefits at household level and its impact on food quality in terms of microbial and nutritional value changes.

Encapsulation of epigallocatechin gallate in zein/chitosan nanoparticles for controlled applications in food systems

The objective of this study was to prepare chitosan nanoparticles (CS NPs) coated with zein as a promising encapsulation and delivery system for epigallocatechin gallate (EGCG). The factors influencing the nanoparticle fabrication, including zein concentration, zein/chitosan weight ratio and EGCG encapsulation percentage, were systematically investigated. The physicochemical and structural analysis showed that the electrostatic interactions and hydrogen bonds were the major forces responsible for nanoparticles formation. The transmission electron microscopy study revealed the spherical nature with smooth surface of obtained nanoparticles. The release profile of EGCG showed a burst effect, followed by slow release. EGCG release was relatively higher from zein/chitosan nanoparticles (zein/CS NPs) with higher DPPH scavenging activity, than that of NPs without zein coating in 95% ethanol fatty simulant. These results indicated that controlled-release of EGCG from zein/CS NPs and its corresponding antioxidant activities in 95% ethanol fatty simulant may provide long-term protection against oxidation for fatty foods.

Carbon dioxide and oxygen gas sensors-possible application for monitoring quality, freshness, and safety of agricultural and food products with emphasis on importance of analytical signals and their transformation

Intelligent packaging technologies are rapidly gaining interest in the agriculture and food industries. Intelligent packaging for agricultural and food products has great potential to improve the shelf life and safety of agricultural and food products apart from its basic functions of keeping the products clean and protecting against unwanted physical and chemical changes. Intelligent packaging components are not limited to radio frequency identification (RFID) sensors, time-temperature indicators, ripeness indicators, and biosensors. Carbon dioxide, oxygen gas sensors and nanobiosensor can be used for real-time monitoring of freshness or quality for agricultural and food products. In this review, details of different sensors that are primarily used for carbon dioxide or oxygen gas sensing and their possible potential to be incorporated into agricultural and food packaging for product quality monitoring are discussed. In addition, special emphasis is placed on detailing the importance of analytical signals and their transformation, because these aspects play crucial role in monitoring the quality and freshness of agricultural and food products via intelligent packaging systems. Signal transducers contribute to the establishment of communication between the product quality sensor and the communication components such as RFID sensors in smart packaging systems by converting a signal in one form of energy to another form.

Potential applications of nonthermal plasmas against biofilm-associated micro-organisms in vitro.

Biofilms as complex microbial communities attached to surfaces pose several challenges in different sectors, ranging from food and healthcare to desalination and power generation. The biofilm mode of growth allows microorganisms to survive in hostile environments and biofilm cells exhibit distinct physiology and behaviour in comparison with their planktonic counterparts. They are ubiquitous, resilient and difficult to eradicate due to their resistant phenotype. Several chemical‐based cleaning and disinfection regimens are conventionally used against biofilm‐dwelling micro‐organisms in vitro. Although such approaches are generally considered to be effective, they may contribute to the dissemination of antimicrobial resistance and environmental pollution. Consequently, advanced green technologies for biofilm control are constantly emerging. Disinfection using nonthermal plasmas (NTPs) is one of the novel strategies having a great potential for control of biofilms of a broad spectrum of micro‐organisms. This review discusses several aspects related to the inactivation of biofilm‐associated bacteria and fungi by different types of NTPs under in vitro conditions. A brief introduction summarizes prevailing methods in biofilm inactivation, followed by introduction to gas discharge plasmas, active plasma species and their inactivating mechanism. Subsequently, significance and aspects of NTP inactivation of biofilm‐associated bacteria, especially those of medical importance, including opportunistic pathogens, oral pathogenic bacteria, foodborne pathogens and implant bacteria, are discussed. The remainder of the review discusses majorly about the synergistic effect of NTPs and their activity against biofilm‐associated fungi, especially Candida species.

Microbial Decontamination of Dried Alaska Pollock Shreds Using Corona Discharge Plasma Jet: Effects on Physicochemical and Sensory Characteristics.

Nonthermal techniques for microbial decontamination are becoming more common for ensuring food safety. In this study, a corona discharge plasma jet (CDPJ) was used for inactivation of microbial contaminants of dried Alaska pollock shreds. Corona plasma jet was generated at a current strength of 1.5 A, and a span length of 25 mm was maintained between the electrode tip and the sample. Upon the CDPJ treatment (0 to 3 min) of dried shreds, microbial contaminants namely aerobic and marine bacteria, and Staphylococcus aureus were inactivated by 2.5, 1.5, and >1.0 log units, respectively. Also, a one-log reduction of molds and yeasts contaminants was observed. The inactivation patterns are fitted well to the pseudo-first-order kinetics or Singh-Heldman model. The CDPJ treatment did not exert statistically significant (P > 0.05) changes in physicochemical properties, namely color characteristics, volatile basic nitrogen, and peroxide value of dried fish shreds, with some exceptions, as compared to untreated controls. Furthermore, CDPJ treatment had no significant impact on the sensory characteristics of dried fish shreds.

Preparation and characterization of antioxidant edible chitosan films incorporated with epigallocatechin gallate nanocapsules

Antioxidant edible films based on chitosan hydrochloride (CHC) and epigallocatechin gallate (EGCG)-loaded nanocapsules (NCs) were developed. The CHC films incorporated with NCs were prepared by a casting method in three different proportions. The obtained films were characterized using the techniques including scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. Meanwhile, the mechanical and color properties, optical transmittance, EGCG release profile and antioxidant activity were also determined. The addition of NCs to CHC films increased their tensile strength (TS) and the percent elongation at break (%E). Lightness was significantly decreased in the NCs embedded films compared to controls, which in turn led to high antioxidant activity and excellent barrier properties against visible light. EGCG was rapidly released into food simulant although the concentration fluctuates over time. Therefore, these films can prevent the oxidation of fatty food stuffs.

Microwave-assisted pretreatment technologies for the conversion of lignocellulosic biomass to sugars and ethanol: a review

Lignocellulosic biomass conversion to biofuels such as ethanol and other value-added bio-products including activated carbons has attracted much attention. The development of an efficient, cost-effective, and eco-friendly pretreatment process is a major challenge in lignocellulosic biomass to biofuel conversion. Although several modern pretreatment technologies have been introduced, few promising technologies have been reported. Microwave irradiation or microwave-assisted methods (physical and chemical) for pretreatment (disintegration) of biomass have been gaining popularity over the last few years owing to their high heating efficiency, lower energy requirements, and easy operation. Acid and alkali pretreatments assisted by microwave heating meanwhile have been widely used for different types of lignocellulosic biomass conversion. Additional advantages of microwave-based pretreatments include faster treatment time, selective processing, instantaneous control, and acceleration of the reaction rate. The present review provides insights into the current research and advantages of using microwave-assisted pretreatment technologies for the conversion of lignocellulosic biomass to fermentable sugars in the process of cellulosic ethanol production.

Effect of corona discharge plasma jet on surface‐borne microorganisms and sprouting of broccoli seeds

BACKGROUND Different pathogenic microorganisms have been reported to cause sprouts-associated outbreaks. In order to sterilise and enhance the germination of seeds, non-thermal plasma has been increasingly investigated in the field of agricultural science as an alternative to the traditional pre-sowing seed treatments. This work aimed to evaluate the effect of corona discharge plasma jet (CDPJ) on disinfection of the natural bio-contaminants of broccoli seed and also studied the plasma effect on sprout seed germination rate and physico-chemical properties of sprouts. RESULTS Aerobic bacteria, moulds and yeasts, B. cereus, E. coli, Salmonella spp. were detected on the broccoli seed surface. After 0-3 min treatment using CDPJ, the detected microorganisms were reduced in the range of 1.2-2.3 log units. Inactivation patterns were better explained using pseudo-first-order kinetics. The plasma treatment of seeds up to 2 min exhibited a positive effect on germination rate, seedling growth. The physico-chemical and sensory characteristics of sprouts were unaffected due to the CDPJ treatment of their respective seeds. CONCLUSION Corona discharge plasma jet can potentially be used for microbial decontamination of broccoli seeds. In addition, the plasma treatment of broccoli sprout seeds has enabled a significant enhancement in their germination rate and seedling growth without compromising physico-chemical and sensory characteristics of their corresponding sprouts.