Pranita Jaiswal

Measurement techniques and application of electrical properties for nondestructive quality evaluation of foods—a review

Non-destructive systems are recent trends for quality evaluation of fruits and vegetables. Information on post-harvest variations in electrical properties is needed to develop new instruments for this purpose. Electrical properties are finding increasing application in agriculture and food processing industries. Knowledge of dielectric properties of foods as a function of moisture content and temperature is essential in the design and control of drying systems. As simple, rapid and non-destructive measuring techniques, dielectric spectroscopy provides information about the dielectric response of materials to electromagnetic field. Electrical properties of agricultural materials have been of interest for many years. The interest in dielectric properties of materials has historically been associated with the design of electrical equipment. This review paper covers theoretical aspects of different electrical properties, their measurement techniques, applications of dielectric properties in agriculture/food processing sector and potential applications of thermal imaging (TI) for quality and safety assessment in food processing. The values of dielectric properties of a number of products including food grains, fruits and vegetables, and meat and meat products are presented in table form. This comprehensive coverage will be useful for academic, scientific and industrial community in treating and applying the facts in developing/testing new processes and products based on electromagnetic energy application.

Rediscovering cyanobacteria as valuable sources of bioactive compounds (Review)

Cyanobacteria are a simple, but primitive and diverse group of microorganisms, with characteristics in common to both bacteria and algae. Their success as a group in a wide range of habitats has been attributed to their unique physiological characters and high adaptive ability under a wide range of environmental conditions. The potential of cyanobacteria as a source of a variety of compounds such as polysaccharides, lipids, proteins, vitamins, sterols, enzymes, pharmaceuticals and other fine chemicals is well recognized, and their demand is now on an increasing trend. This compilation reviews the salient advances in the discovery of bioactive compounds from cyanobacteria and their significance in agriculture and industry.

Cyanobacterial diversity in the rhizosphere of rice and its ecological significance

This investigation was undertaken to characterize the abundance and genera-wise diversity of cyanobacteria in the rice rhizosphere and nitrogen-fixing ability of the isolated strains. The cyanobacterial strains belonging to the genera Nostoc and Anabaena comprised 80% of the rhizosphere isolates, which were also efficient in enhancing the germination and growth of wheat seeds and exhibited significantly high protein accumulation and IAA production. Distinct profiles for the cyanobacterial strains were obtained on amplification with extended Hip 1 primer — HipTG, indicative of the diversity among these strains. Our investigation helped in identifying promising cyanobacterial isolates from the rhizosphere of rice, which can be utilized in developing efficient plant growth promoting cyanobacterial inoculants.

Physiological characterization and electron microscopic investigation of cyanobacteria associated with wheat rhizosphere

Physiological attributes of a set of cyanobacterial strains, isolated from the rhizosphere of wheat (var. HD 2687), identified as belonging to the genera Calothrix (n = 3), Westiellopsis (1), Hapalosiphon (2) and Nostoc (2), were axenized and evaluated. The concentrated culture filtrates of three cyanobacterial strains — C. ghosei, H. intricatus and Nostoc sp. were able to enhance germination percentage, radicle and coleoptile length in inhibition experiments with wheat seeds. Indole-3-acetic acid (IAA) production was recorded in light and dark (+0.5 % glucose) incubated cultures. Incubation in the presence of tryptophan significantly enhanced IAA production. Acetylene-reducing activity was higher in light incubated cultures of Nostoc sp. followed by C. ghosei, while in the dark, C. ghosei recorded highest values. TLC of the filtrates revealed the presence of several amino acids such as histidine, and auxin-like compounds. Co-culturing with selected strains recorded significant enhancement in plant chlorophyll. Root sections of wheat seedlings co-cultured with C. ghosei revealed the presence of short filaments inside the root hairs and cortical region. Such strains can be promising candidates for developing plant growth promoting associations for wheat crop, besides serving as model systems for understanding the metabolic interactions of cyanobacteria with host plant, such as wheat.

Detection and quantification of soymilk in cow–buffalo milk using Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR–FTIR)

Milk consumption is steadily increasing, especially in India and China, due to rising income. To bridge the gap between supply and demand, unscrupulous milk vendors add milk-like products from vegetable sources (soymilk) to milk without declaration. A rapid detection technique is required to enforce the safety norms of food regulatory authorities. Fourier Transform Infrared (FTIR) spectroscopy has demonstrated potential as a rapid quality monitoring method and was therefore explored for detection of soymilk in milk. In the present work, spectra of milk, soymilk (SM), and milk adulterated with known quantity of SM were acquired in the wave number range of 4000-500cm(-1) using Attenuated Total Reflectance (ATR)-FTIR. The acquired spectra revealed differences amongst milk, SM and adulterated milk (AM) samples in the wave number range of 1680-1058cm(-1). This region encompasses the absorption frequency of amide-I, amide-II, amide-III, beta-sheet protein, α-tocopherol and Soybean Kunitz Trypsin Inhibitor. Principal component analysis (PCA) showed clustering of samples based on SM concentration at 5% level of significance and thus SM could be detected in milk using ATR-FTIR. The SM was best predicted in the range of 1472-1241cm(-1) using multiple linear regression with coefficient of determination (R(2)) of 0.99 and 0.92 for calibration and validation, respectively.

Cyanobacteria as potential options for environmental sustainability — promises and challenges

Cyanobacteria represent an ancient group of photosynthetic prokaryotes, whose ubiquity, metabolic flexibility and adaptive abilities have made them a subject of research worldwide. These structurally simple organisms combine in themselves interesting facets of plant and bacterial metabolism, which is amenable to genetic exploitation. Despite their globally recognized significance in the sustenance of fertility in rice based cropping systems, they have not been tapped for their extraordinary repertoire of activities, especially their beneficial role as biological agents in remediation and amelioration of soil and water environment and as sinks for greenhouse gases. The information available on these aspects and future lines of research for more efficient utilization of these microorganisms is presented.

Modulation of biocidal activity of Calothrix sp. and Anabaena sp. by environmental factors

An investigation was undertaken to evaluate a set of cyanobacterial strains in terms of production of biocidal compounds exhibiting allelochemical and fungicidal properties. Two cyanobacterial strains — Anabaena sp. and Calothrix sp. were selected for further investigation, on the basis of their larger inhibition zones on the lawn of Synechocystis and Synechococcus sp. and two phytopathogenic fungi — Rhizoctonia bataticola and Pythium debaryanum. The diameter of the inhibition zone was largest when extracellular filtrates of the two cultures incubated at high light intensity (90–100 μmol photons m−2 s−1) and temperature (40 ± 2 °C) or grown in medium containing two-folds higher P (1.4 mg/L, as compared to 0.7 mg/L in BG 11 medium) were taken. A pH of 8 was the most optimal for both strains, in terms of growth and biocidal activity. Partial purification of ethyl acetate extract using TLC, followed by GLC revealed a single peak. This study highlights the importance of environmental factors in aggravating or reducing the toxic effects of these harmful cyanobacteria and their potential as a biocontrol agent.

Stimulation of pigment accumulation inAnabaena azollae strains: Effect of light intensity and sugars

The influence of high light intensity on the growth and pigment accumulating ability ofAnabaena azollae was investigated.A. azollae responded positively to high light intensity (6 klx) and was further evaluated at higher intensities (10 and 15 klx), in the presence of glucose, sucrose and jaggery ± DCMU. Significant enhancement in phycobiliproteins and carotenoids was observed in the sugar supplemented cultures at high light intensities. SDS-PAGE profiles of whole cell proteins revealed the presence of unique bands in such treatments. Sucrose supplementation induced a 30–90% increase in carotenoids, phycocyanin and phycoerythrin content at 10 klx. Molecular analysis of the stimulatory and interactive role of sugars on pigment enhancement at high light intensity may aid in better exploitation of cyanobacteria as a source of pigments.

Development of alternative support system for viable count of cyanobacteria by most probable number method

A technique was developed to evaluate alternative support systems to test tubes used in the standard most probable number technique, for simultaneous isolation and enumeration of cyanobacteria. Five different support systems were tested for their suitability in terms of accuracy, sensitivity, economics and ease of handling. PCR plates with 96 wells and carrying capacity of 300 µL per well were found to be most sensitive, besides being cost- and time-effective. This technique can also be useful for isolation of cyanobacteria, due to immobilization of colonies in the gel matrix and storage of samples at room temperature, without loss of viability for 5–6 weeks. This technique can help to process large sample size with ease — both for enumeration and isolation and can be extended for enumeration of other microorganisms from diverse sources.

Textural properties of mango cultivars during ripening

Firmness and toughness of fruit, peel and pulp of seven different mango cultivars were studied over a ripening period of ten days to investigate the effects of harvesting stages (early, mid and late) on fruit quality. Parameters were measured at equatorial region of fruits using TA-Hdi Texture Analyzer. The textural characteristics showed a rapid decline in their behaviour until mangoes got ripened and thereafter, the decline became almost constant indicating the completion of ripening. However, the rate of decline in textural properties was found to be cultivar specific. In general, the changes in textural attributes were found to be significantly influenced by ripening period and stage of harvesting, but firmness attributes (peel, fruit and pulp) of early harvested mangoes did not differ significantly from mid harvested mangoes, while peel, fruit and pulp firmness of late harvested mangoes were found to be significantly lower than early and mid harvested mangoes.