Isolation and characterisation of selected lactic acid bacteria for improved processing of Nem chua, a traditional fermented meat from Vietnam.

Nem chua is a traditional lactic acid fermented meat of Vietnam that is consumed raw. During fermentation, the number of acid-producing bacteria increased significantly and by the final day (4th), it had reached approximately 8.4 log cfu/g, contributing to 94% of the total microbiota of the product. Out of 85 isolates obtained from the product, only 44 were confirmed Gram-positive and catalase-negative. These putative LAB isolates were purified and screened for antimicrobial and proteolytic activity. None of the isolates showed bacteriocin activity using the 'spot-on lawn' method, but showed antimicrobial activity against Lactobacillus sakei and Enterococcus faecium using deferred assay. Four isolates showed good proteolytic activities at pH 7.0. These isolates were identified as Lactobacillus plantarum using an API 50 CHL i.d. kit. Sequencing of the partial 16S rRNA gene amplified by primers 1101F (5'-AACGAGCGCAACCC-3') and 1407R (5'-GACGGGCGGTGTGTAC-3') showed 98% homology to Lactobacillus plantarum WCFS1.

Genetic variation in the physical properties of sweet potato starch.

Sweet potato starch, prepared from 44 genotypes adapted to Philippine conditions, showed wide variation and distinctly different pasting profiles in Rapid Visco-Analyzer (RVA) analysis at 11% and 7% starch concentration. At 11% starch concentration, the pasting profiles were type A, characterized by high to moderate peak with a major breakdown and low cold paste viscosity. At 7%, the pasting profile was generally type C, characterized by the absence of a distinct peak with none to very slight breakdown and high cold paste viscosity. However, differentiation among genotypes was better achieved from RVA pasting profiles at 11% starch concentration. Peak viscosity (PV) and hot paste viscosity (HPV) at 11% starch paste concentration had significant negative correlation with amylose content. PV, HPV, and setback ratio were significantly correlated to adhesiveness of the starch gel. Sweet potato starch generally had high swelling volume but low solubilities at 92.5 degrees C.

Milk Films Exposed to High Humidity: Studies with Electron Microscopy and Electrophoresis 1, 2.

Stainless steel plates, which are similar to milk contact surfaces, were dipped in fresh raw milk. The residual film was dried (37 C and 10% to 20% relative humidity) for 30 min. Treated plates were then exposed to 100% relative humidity for 30 min at 37 C. Scanning electron microscopy revealed splotches of fat on surfaces of dried films and the humidified films had a more aggregated and porous appearance than films that were dried only. The incidence of granulated lactose was greater among humidified samples than among nonhumidified samples. Discontinuous polyacrylamide gel electrophoresis revealed that α- and ß-caseins resisted rinsing from plates on which dried films were exposed to 100% relative humidity but not from plates on which films had been dried only.

Factors Influencing Tenacity of Dried Milk Films Exposed to High Humidity 1, 2.

Rinsability of milk films on stainless steel was impaired by exposure to 100% relative humidity (RH). Rinsability was determined by automated Lowry protein tests of detergent used to remove films. Residue of milk films was 1% of the initial soil load when dried on stainless steel plates without humidification, but was 6.35% of the initial load after drying (30 min), humidification (15 min) and redrying (30 min) all at 37 C. Three successive exposures to 100% RH for 7.5 min at 37 C, each followed by 30 min of drying, yielded a residue of nearly 30% of the initial soil load. Exposure at 37 C produced the maximum amount of residue on plates. Experimental temperatures ranged from 0 to 75 C. Temperature of milk applied to plates was of little importance. Raw milk formed more tenacious film than skim milk or major components of milk. Milk produced during colder months yielded less soluble films than milk produced during warmer months. Lowering of milk pH to 5.7, adding soluble calcium, and aging milk at 0 C increased residues. Chelation of soluble calcium with EDTA or dissociation of milk protein with sodium dodecyl sulfate decreased soil residue levels. Exposure of instantized nonfat dry milk to the high humidity treatment decreased its solubility more than tenfold.