Prabir K. Sarkar

Microbiological quality of some retail spices in India

Abstract A total of 154 samples of 27 kinds of spices from retail shops of 20 States of India was investigated to determine their microbial status. As per ICMSF specifications, the total aerobic mesophilic bacteria (TAMB) count showed that 51% of the samples were in the unacceptable level (>106 cfu g−1). While moulds were detected in 97% of the samples, yeast was found in only one. Bacillus cereus, Clostridium perfringens, Staphylococcus aureus and members of Enterobacteriaceae occurred in 85, 59, 11 and 85%, respectively of the kinds. Whereas black pepper powder, caraway, garlic and red chilli did not contain B. cereus, this foodborne pathogen was found in all the samples of ajmud, small cardamom and cumin powder. Coliforms and faecal coliforms were found in 33 and 15%, respectively of the kinds. Escherichia coli was detected in only one sample, of garlic. Salmonella and Shigella were found only in 2.6% of the samples. Although they contained less TAMB, the non-packaged spices had a higher load of moulds, B. cereus and Enterobacteriaceae than that of polyethylene-packaged ones.

Bacillus fermentation of soybeans.

Kinema fermentations of Indian and Canadian No. 1 soybeans by Bacillus sp. DK-W1 and by mixed cultures of Bacillus sp. DK-W1 and Enterococcus faecium DK-C1 were essentially identical. The viable cell count of Bacillus increased from an initial 105 to 1010 c.f.u./g wet wt after 48 h incubation at 37°C. The pH of the fermentation dropped from an initial 6.9 to about 6.4 after 8 h and then rose to 8.6 after 32 h, with a coincident increase in proteolytic activity and ammonia concentration. The fermentations containing E. faecium and Bacillus exhibited a greater initial pH decline and a slightly retarded subseqent increase in pH compared with fermentations with Bacillus only. The presence of E. faecium had no detectable effects on growth of the Bacillus, proteolytic activity, ammonia production or the final pH of the fermentations.

Microbiology of mesu, a traditional fermented bamboo shoot product

The use of mesu as a pickle and as the base of curry is a tradition in the Darjeeling hills and Sikkim of India. A total of 327 strains of lactic acid bacteria, representing Lactobacillus plantarum, L. brevis and Pediococcus pentosaceus were isolated from 30 samples of mesu. These species were present in all samples of raw bamboo shoots tested. Mesu was dominated by L. plantarum followed by L. brevis; P. pentosaceus was isolated less frequently and recovered from only 40-50% of the mesu samples. The fermentation was initiated by P. pentosaceus, followed by L. brevis, and finally succeeded by L. plantarum species. During fermentation, the titratable acidity increased from 0.04 to 0.95%, resulting in the decline in pH from 6.4 to 3.8.

Changes in the microbial profile and proximate composition during natural and controlled fermentations of soybeans to produce kinema

The mean viable count of Bacillus subtilis, Enterococcus faecium and Candida parapsilosis increased progressively in fermenting soybeans; the increase was significant at every sampling time interval (8 h) up to 48, 40 and 32 h, respectively. Although acidity increased significantly at almost every 8 h interval, the fermentation was essentially alkaline, causing pH of the beans to rise to about 8·5. With the decline in protein nitrogen content, the non-protein and soluble nitrogen contents increased significantly at almost every 8 h interval. The fermentation process as well as general acceptability of kinema were improved by fermenting sterile beans with B. subtilis DK-WI at 45°C. This led to a more desirable fermentation within a much shorter period, compared with the natural fermentation. The rate of increase of Bacillus count in monoculture fermentation was much faster than that in natural fermentation. The Bacillus count in kinema produced by monoculture fermentation was 6·4 times higher than that of naturally fermented kinema. The content of free fatty acids of the Bacillus -fermented kinema was 140% less than that of the naturally fermented one. However in respect of other compositional parameters, the two types of fermentation were similar.

Microbiological safety of kinema, a fermented soya bean food

Abstract Kinema is a fermented soya bean food of Nepal and the hilly regions of North-eastern States of India. Generally, the fermentation is dominated by Bacillus spp. that often cause alkalinity and desirable stickiness in the product. The present study was undertaken in a limited number of commercial (market) kinema samples to test for the presence of foodborne pathogens and their properties. Bacillus cereus was present in numbers exceeding 10 4 cfu/g product in five of the tested 15 market samples. Enterobacteriaceae and coliform bacteria exceeded 10 5 cfu/g in 10 of the 15 samples. Escherichia coli exceeding 10 5 cfu/g was found in two samples. Staphylococcus aureus was not detected in any of the tested samples. Of 31 isolated typical and atypical strains of B. cereus , 18 representative strains were tested qualitatively for the ability to produce diarrhoeal type enterotoxin (BCET) using an Oxoid BCET-RPLA test kit. Overall, BCET was formed by 12 strains in BHIG (brain heart infusion broth +1% glucose), by seven strains on sterilized cooked rice, and by five strains on sterilized cooked soya beans. Semi-quantitative tests on BCET revealed that levels exceeding 256 ng/g soya beans, produced by single pure culture inoculation with the isolated B. cereus strains, were reduced to ≤ 8 ng/g by frying kinema in oil, a common procedure when making kinema curry. It was also shown in a mixed pure culture experiment that a kinema strain B. Subtilis DK-W1, is able to suppress growth and BCET formation by a selected toxin producing strain (BC7-5) of B. cereus . It is concluded that the traditional way of making kinema and its culinary use in curries is safe. However, for novel applications of kinema, safety precautions are advisable.

B-group vitamin and mineral contents of soybeans during kinema production

Concentrations of several B-group vitamins, determined by high-performance liquid chromatography (HPLC), and minerals, determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES), in soybeans during different kinema production stages were compared. After soaking soybeans in water, thiamine (B1) content decreased, whereas riboflavin (B2) content remained unchanged. Cooking had no influence on the B1 content, but it enhanced the level of B2 and niacin (B3). Incubation of beans at 37°C for 48 h, when mixed with Bacillus subtilis, caused an increase in concentration of both B1 and B2. Vitamin B1 levels decreased when either Enterococcus faecium accompanied B subtilis or the temperature was elevated for 18 h fermentation. Traditionally prepared kinema contained 8 mg B1, 12 mg B2, 45 mg B3, 683 mg Ca, 4 mg Cu, 18 mg Fe, 494 mg Mg, 10 mg Mn, 1257 mg P, 2077 mg K, 13 mg Zn and <0·5 mg of Cd, Cr, Pb, Ni and Na per kg dry matter. While the vitamin B1 content was significantly (P<0·05) higher, the contents of vitamins B2 and B3 were significantly (P<0·05) lower in raw soybeans than those in kinema. Mineral concentrations were 3·1–8·3 times higher in raw soybeans than in kinema.

Inhibitory effect of garlic on bacterial pathogens from spices

An unconventional technique for primary screening of bacterial susceptibility to garlic (Allium sativum Linn.), using a slice from its clove, was described. Aqueous extracts of garlic were found to possess a potent bacteriostatic principle against Gram-positive as well as Gram-negative foodborne bacterial pathogens. In agar medium, the minimum inhibitory concentrations (MICs) of garlic were 6–10 mg ml−1 for Bacillus cereus, 30–40 mg ml−1 for Staphylococcus aureus (excepting the isolate from garlic, where the MIC was 100 mg ml−1), 20–30 mg ml−1 for Clostridium perfringens, 10 mg ml−1 for Escherichia coli (30 mg ml−1 for the garlic isolate), 40–100 mg ml−1 for Salmonella, and 10–40 mg ml−1 for Shigella. It inhibited the growth of all these strains, which were resistant to some commonly used antibiotics. Most of the tested strains were resistant to penicillins, although sensitive to garlic. While the growth of B. cereus and Cl. perfringens was completely inhibited at 10 and 70 mg garlic, respectively, ml−1 test broth, their respective enterotoxin production ceased at 10 and 50 mg garlic ml−1.

Response surface optimisation of antioxidant extraction from kinema, a Bacillus-fermented soybean food

The objective of this work was to optimise different parameters (solvent concentration, time and temperature) for antioxidant extraction from kinema, demonstrated by total phenol content (TPC) and DPPH-scavenging activity (DSA), using response surface methodology. A central composite design was performed to determine the effect of solvent concentration (methanol, 30-100%), temperature (30-60°C) and time (30-150min) on the TPC and DSA of the extract. The solvent concentration and temperature had the most significant (p<0.05) effect. The optimum conditions for the TPC extraction and DSA were 100% methanol, 50°C and 30min, in which 140mg of gallic acid equivalent (GAE) g-1 lyophilised extract and 52% DSA were predicted, while 135mg GAE g-1 lyophilised extract and 56% DSA were experimentally obtained. No significant difference (p<0.05) was found between the experimental and predicted values of the response variables.

Optimization of soybean processing into kinema, a Bacillus‐fermented alkaline food, with respect to a minimum level of antinutrients

Optimization of traditional processing of soybeans using response surface methodology (RSM) to achieve a minimum level of antinutritional factors (ANFs) in kinema.

Response surface optimisation of extraction of antioxidants from strawberry fruit, and lipid peroxidation inhibitory potential of the fruit extract in cooked chicken patties

BACKGROUND Strawberries contain high levels of antioxidants and have beneficial effects against oxidative stress-mediated diseases, such as cancer. They contain multiple phenolic compounds, which contribute to their biological properties. Hence, a study was carried out to optimise the extraction of antioxidants and evaluate the antioxidant potential of strawberry fruit extract (SE) in cooked chicken patties during refrigerated storage. The activity of SE was compared with that of butylhydroxytoluene (BHT). RESULTS The effect of solvent type (MeOH and EtOH), concentration (0-70%) of EtOH in the system, temperature (30-60 °C), and time (30-150 min) on DPPH•-scavenging activity of SE was investigated. Response surface methodology was used to estimate the optimum extraction conditions for each parameter. The maximum predicted DPPH• scavenging under the optimised conditions (100% MeOH, 30 °C, 150 min) was 43% at 1 mg SE mL⁻¹. Freshly prepared chicken patties were treated with 5% and 10% SE and 2% BHT, and stored aerobically at 4 °C for 6 days. SE had no influence (P < 0.05) on any of the sensory attributes of the patties. The values of thiobarbituric acid reactive substances reduced significantly (P < 0.05) from 2.47 mg in control patties to 0.312 mg and 0.432 mg malonaldehyde kg⁻¹ sample in 5-SE and 10-SE patties, respectively, on the day 6 of storage. CONCLUSION The optimised model depicted MeOH at 30 °C with an extended time of 150 min as the optimum settings for extraction of compounds from strawberry that had the scavenging activity. The study shows that the extraction of natural antioxidants from strawberry can be improved by optimising several key extraction parameters. SE also acted as an effective antioxidant and suppressed lipid peroxidation in cooked chicken patties.