Ana I.E. Pintado

Interrelationships among Microbiological, Physicochemical, and Biochemical Properties of Terrincho Cheese, with Emphasis on Biogenic Amines

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 ewes 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.

Caseinolytic activity of fruit extract from Opuntia ficus-indica on bovine, caprine, and ovine sodium caseinates

The rates and extents of hydrolysis of αS‐ and β‐caseins from bovine, caprine, and ovine sodium caseinates produced by an enzymatic extract of the fruit of Opuntia ficus‐indica, (L.) Miller were evaluated and compared with those produced by a commercial animal rennet. A mechanistic model based on a pseudo‐first‐order enzymatic reaction, in the presence of first‐order deactivation of the enzyme, was postulated and successfully fitted to the experimental data. The animal rennet exhibited higher enzymatic efficiency than the fruit extract, irrespective of the source (i.e., bovine, caprine, or ovine) and the type (i.e., αS‐ or β‐casein) of substrate. The enzymatic efficiency (kcat/Km) for αS‐casein ranged from 72 to 220 and from 43 to 65 L g−1 h−1, and for β‐casein from 242 to 742 and from 55 to 164 L g−1 h−1, for the animal rennet and the enzymatic extract of O. ficus‐indica, respectively. Finally, it was observed that β‐casein from caprine and ovine caseinates was degraded by O. ficus‐indica faster than its αS counterpart, but the reverse was observed for bovine caseinate.

Consumer acceptance and sensory profiling of reengineered kitoza products.

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 Profiles 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.