Incidence of Listeria monocytogenes and Listeria spp. in a small-scale mushroom production facility.

Listeria monocytogenes is a foodborne pathogen of significant concern to the agricultural and food processing industry because of its ability to grow and persist in cool and moist environments and its association with listeriosis, a disease with a very high mortality rate. Although there have been no listeriosis outbreaks attributed to fresh mushrooms in the United States, retail surveys and recalls are evidence that L. monocytogenes contamination of mushrooms (Agaricus bisporus) can occur. The objective of this study was to determine the prevalence of Listeria spp., including L. monocytogenes, in a small-scale mushroom production facility on the campus of the Pennsylvania State University in the United States. Of 184 samples taken from five production zones within the facility, 29 (15.8%) samples were positive for Listeria spp. Among the Listeria spp. isolates, L. innocua was most prevalent (10.3%) followed by L. welshimeri (3.3%), L. monocytogenes (1.6%), and L. grayi (0.5%). L. monocytogenes was recovered only from the phase I raw material composting area. Isolates of L. monocytogenes were confirmed and serotyped by multiplex PCR. The epidemiological relatedness of the three L. monocytogenes isolates to those serotypes or lineages frequently encountered in listeriosis infections was determined by multi-virulence-locus sequence typing using six virulence genes, namely, prfA, inlB, inlC, dal, clpP, and lisR. The phylogenetic positions of the three isolates in the dendrogram prepared with data from other isolates of L. monocytogenes showed that all isolates were grouped with serotype 4a, lineage IIIA. To date, this serotype has rarely been reported in foodborne disease outbreaks.

Occurrence of aflatoxin M(1) 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.

Preparation of N-vanillyl chitosan and 4-hydroxybenzyl chitosan and their physico-mechanical, optical, barrier, and antimicrobial properties.

Chitosan derivatives such as N-vanillyl chitosan and 4-hydroxybenzyl chitosan were prepared by reacting chitosan with 4-hydroxy-3-methoxybenzaldehyde (vanillin) and 4-hydroxybenzaldehyde. Amino groups on chitosan reacts with these aldehydes to form a Schiff base intermediate, which is later on converted into N-alkyl chitosans by reduction with sodium cyanoborohydride. The chemical reaction was monitored by 1H NMR spectroscopy and the absence of aldehydic proton at 9.83ppm in NMR spectra was observed for both the modified chitosan derivatives confirming the reaction. Modified chitosan films were later prepared by solution casting method and their physico-mechanical, barrier, optical and thermal properties were studied. The results clearly indicated significant change in tensile strength, water vapour transmission rate, and haze properties of modified chitosans. Modified chitosan films were also studied for their antimicrobial activity against Aspergillus flavus. The results showed a marked reduction of aflatoxins produced by the fungus in the presence of the N-vanillyl chitosan and 4-hydroxybenzyl chitosan film discs to 98.9% and non-detectable levels, respectively.

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.