Prema Viswanath

Anaerobic digestion of fruit and vegetable processing wastes for biogas production.

Abstract The effect of feeding different fruit and vegetable wastes, mango, pineapple, tomato, jackfruit, banana and orange, was studied in a 60-liter digester by cycling each waste every fifth day in order to operate the digester as and when there was supply of feed. The characteristics of the anaerobically digested fluid and digester performance in terms of biogas production were determined at different loading rates (LR) and at different hydraulic retention times (HRT), and the maximum biogas yield of 0·6 m 3 /kg VS added was achieved at a 20-day HRT and 40 kg TS m −3 day −1 loading rate. The hourly gas production was observed in the digesters operated at 16 and 24 days HRT. The major yield (74·5%) of gas was produced within 12 h of feeding at a 16-day HRT whereas at a 24-day HRT only 59·03% of the total gas could be obtained at this time.

Occurrence of aflatoxin M1 in some samples of UHT, raw & pasteurized milk from Indian states of Karnataka and Tamilnadu

Aflatoxin M(1) (AFM(1)) is a toxic metabolite found in the milk of lactating animals which have consumed feedstuffs contaminated with aflatoxin B(1). Ultra high temperature treated (UHT) milk is a product which is becoming popular in developing countries like India as there is a lack of proper cold storage or refrigeration facilities. In this study, 45 samples of UHT milk of popular brands prevalent in the market were analyzed for the presence of AFM(1) by reversed phase HPLC using fluorescent detector after cleanup of sample with immunoaffinity columns. All samples of plain UHT milk were positive for AFM(1) and 38% of these contained levels more than 0.5 μg/kg, the maximum permitted limit prescribed by the Codex Alimentarius Commission and by the mandatory regulations of the country, the FSSAI Regulations, 2011. In 62.5% of flavored UHT milk, AFM(1) was below detectable levels (0.02 μgL(-1)). However, 12.5% of these samples also contained levels exceeding the maximum permitted limits. AFM(1) was present in 61.6% of the 52 raw milk samples analyzed from the two states of Karnataka and Tamilnadu with a range of 0.1-3.8 μgL(-1). 17.3% of these samples also exceeded the regulatory limits of the country.

Anaerobic digestion of canteen wastes for biogas production : process optimisation

Abstract The canteen and mess wastes (CMW) which are rich in organic constituents were employed in this study for biogas generation. Some of the environmental and operational parameters influencing biogas yield and its methane content were optimised in a 200 l Khadi and Village Industries Commission of India digester. A high gas yield of 0·981 m 3 kg −1 volatile solids (VS) added with a methane content of 50% was obtained, i.e., about 65% substrate utilisation. The hydraulic retention time (HRT) was successfully reduced to 20 days, while the loading rate reached as high as 100 kg total solids (TS) m −3 d −1 . Thus the anaerobic digestion of CMW forms an effective ‘two-in-one systems’ involving waste utilisation and energy generation.

Anaerobic digestion of silk industry wastes

Abstract In order to determine biogas potential of defatted silk worm pupae waste, anaerobic batch digestion was carried out in a 1-l bioreactor and, based on the results, further experiments were conducted in a 20-l KVIC (Khadi and Village Industries Commission) type digester under semi-continuous feeding. The effect of seven loading rates was studied. The maximum yield of biogas (0·53 m3 kg−1 volatile solids (VS) added) and methane (0·38 m3 kg−1 VS added) was accomplished at a loading rate of 1 kg total solids (TS) m−3 day−1. The methane content was as high as 70%. The hydraulic retention time (HRT) of 30-day digestion exhibited maximum yield of biogas and methane. Ammonia-nitrogen related inhibition of anaerobic digestion was observed. By appropriately adjusting the carbon and nitrogen ratio with carbonaceous substrate it may be possible to exploit the commercial potential of defatted silk worm pupae waste.

Microscopic detection of adulteration of Bengal gram (Cicer arietinum) flour with other legume flour based on the seed testa macrosclereids

Besan, the flour of Bengal gram (Cicer arietinum Linn), a legume, is a popular ingredient of many culinary dishes in India. Because of its high demand, its flour is often adulterated by that of other legumes, such as, Lathyrus sativus (lathyrus) or Pisum sativum (pea) by unscrupulous traders. There are chemical methods of paper chromatography and HPLC by which the adulteration with the flour of L. sativus can be established but they are sophisticated techniques. At present, there are no chemical methods by which the adulteration with the flour of P. sativum can be detected. Microscopy is a simple technique and has been used for detection of adulteration of a number of food grains. Microscopic observation of the flour of these three legumes showed that their seed testa macrosclereids are distinct in their shape and size. The macrosclereids of C. arietinum are longer with a mean length of 155.6 microns and are bent at one end. Those of either P. sativum or L. sativus are shorter with a mean length of 61.8 and 72 microns respectively, with flat ends and with a different morphology. The seed testa macrosclereids of other edible legumes also show differences in morphology. Thus, it was observed that microscopic observation of the besan flour for the macrosclereids of other legumes is a powerful but simple means by which detection of adulteration of besan with the flour of P. sativum or L. sativus or by other edible legumes can be made. These observations make the subject matter of this manuscript.

Influence of penicillin on the stabilization of anaerobic digestion of rain tree kernels for methane generation

Abstract Rain Tree ( Pithecolobium saman Bentham) kernels, rich in fermentable sugars were employed for methane generation through anaerobic digestion using 20- l biodigestors under a semi-continuous feeding mode. A loading rate of 45 g/ l /d resulted in the accumulation of volatile fatty acids (1725 mg/ l ) which led to souring of the digestor. To avoid the excessive production of volatile fatty acids by the non-methanogenic microorganisms and to stabilize the anaerobic digestion process, penicillin was added and a gas yield of 0.49 m 3 /kg VS added with an average methane yield of 0.21 m 3 /kg VS added was obtained.