ABSTRACT
De-Man Rogosa and Sharpe (MRS) is a complex medium commonly used to obtain exopolysaccharides (EPS) from lactic acid bacteria. However, the various nutrients (carbon and nitrogen sources) of media and supplements added to enhance the bacterial growth and EPS production, may interfere with the purification of the extracts resulting in an over-estimation of the EPS and erroneous structural assignments. The efficiency of trichloroacetic acid (TCA)/pronase and 5-sulfosalicylic acid - SSA methods was evaluated. In addition, the interference of the major MRS broth components as well as lactose was evaluated using xanthan gum as model control EPS. It was concluded that MRS medium is a major source of interfering compounds in the quantification of EPS, mainly glucose-rich material and to a lesser extent mannoproteins from yeast extract. This effect was found to be potentiated by the presence of lactose. TCA/pronase method was shown to be more efficient in eliminating interferents.
ABSTRACT
Kitoza refers to a traditional way of preparing beef and pork in Madagascar. However, in order to improve some drawbacks previous identified, the product was submitted to a reengineering process. The acceptance and sensory profiling of improved Kitoza products among Portuguese consumers was investigated. A local smoked loin sausage was selected as basis for comparison. Firstly, a Focus Group study was performed to identify sensory descriptors for Kitoza products and explore product perception. Subsequently, a Flash Profile and a consumer sensory acceptance study were conducted. Flash Profile's results showed that beef- and pork-based Kitoza products investigated differed considerably in all sensory dimensions. The Portuguese sausage was characterized as having a more intense and lasting after taste, as well as displaying a higher degree of (meat) doneness. The acceptance study yielded higher overall liking ratings for pork- than for beef-based Kitoza, although the Portuguese sausage remained the most appreciated product.
Subject(s)
Consumer Behavior , Meat Products/analysis , Animals , Cattle , Female , Focus Groups , Humans , Male , Meat Products/microbiology , Meat Products/standards , SwineABSTRACT
Changes in the microbiological, physicochemical, and biochemical characteristics of Terrincho cheese as represented by native microflora, pH, water activity, soluble nitrogen fractions, free amino acids, and biogenic amines (e.g., ethylamine, dimethylamine, tryptamine, phenylethylamine, putrescine, cadaverine, histamine, tyramine, cystamine, and spermine) during ripening were monitored. Terrincho is a traditional Portuguese cheese manufactured from raw ewe's milk. The main groups of microorganisms (lactococci, lactobacilli, enterococci, pseudomonads, staphylococci, coliforms, yeasts, and molds) were determined following conventional microbiological procedures. Free amino acids and biogenic amines were determined by reverse-phase high-performance liquid chromatography, following extraction from the cheese matrix and derivatization with dabsyl chloride. The total content of free amino acids ranged from 1,730 mg/kg of dry matter at the beginning of the ripening stage to 5,180 mg/kg of dry matter by day 60 of ripening; such an increase was highly correlated with the increase of water-soluble nitrogen in total nitrogen, 12% trichloroacetic acid-soluble nitrogen in total nitrogen, and 5% phosphotungstic acid-soluble nitrogen in total nitrogen throughout ripening. Histamine was consistently present at very low levels, whereas putrescine, cadaverine, and tryptamine were the dominant biogenic amines and increased in concentration during ripening. Ethylamine, tryptamine, phenylethylamine, and cystamine reached maxima by 30 days of ripening and decreased thereafter. Significant correlations between amino acid precursors and corresponding biogenic amines, as well as between biogenic amines and microbial viable numbers, were observed.