Candida and Pseudomonas Lipase-Catalyzed Hydrolysis of Butteroil in the Absence of Organic Solvents

Candida rugosa lipase (CRL) and Pseudomonas fluorescein lipase (PFL) were used to hydrolyze a low-melting point butteroil fraction in the absence of orgaic solvents. CRL and PFL displayed pH activity optima of 6.7 and 7.8, and temperature-activity optima of 40–50°C and 35°C, respectively. Maximum activity for PFL was observed at 5% (v/v) water content. CRL showed higher specificity towards butyric acid relative to PFL after 3 hours of hydrolysis at 40°C (22.3 mol% vs 7.8 mol%, respectively). Both enzymes displayed, however, high specificities towards palmitic and oleic acids. CRL's inherent specificity towards butyric acid makes it an ideal choice for a biological catalyst to generate useful dairy flavor profiles.     

THE EFFECTS OF TURGOR PRESSURE ON PUNCTURE AND VISCOELASTIC PROPERTIES OF TOMATO TISSUE

The effects of turgor pressure on puncture and viscoelastic properties of mature-green tomato pericarp were examined using tissue discs soaked in a range of osmotica (0.0–0.6 M mannitol) for at least 36 h at 4C. Turgor pressure was estimated from the osmotic potential of soaking solutions that induced incipient plasmolysis. Based on volume changes, the osmotic potential and turgor pressure of fresh tissue were estimated to be −0.56 ± 0.08 MPa and 0.20 MPa, respectively. However, puncture and viscoelastic properties corresponded to a turgor pressure of 0.15 MPa. The discrepancy between calculated and actual turgor pressures was attributed to the presence of apoplastic solutes. The data from this study revealed a general increase in cell wall stress, strain and elasticity with increasing turgor. With increases in turgor above that of untreated tissue both wall extensibility and elasticity became limiting and thus cell wall stiffness increased. Conversely, a decrease in turgor below that of untreated tissue led to an increase in viscoelasticity. Increases in bioyield and pseudoplastic bioyield strains with a variation in turgor from that of untreated tissue were consistent with cell debonding as a dominant mechanism of tomato tissue bioyielding. The reduced failure force, deformation and firmness with increasing turgor were consistent with cell rupture as a predominant mechanism of failure of mature-green tomato pericarp tissue.     

Protein composition of milk from Holstein–Friesian dairy cows and its relationship with the genetic variants A and B of κ-casein and β-lactoglobulin (Part I)

The protein composition and the milk yield (morning milking) were studied in 10 Chilean Holstein–Friesian first lactation dairy cows during the spring season. In addition, the genetic variants A and B of κ-casein (κ-CN) and β-lactoglobulin (β-Lg) were also identified. The results showed that the casein content is significantly affected by the presence of B variant of κ-CN. Moreover, positive interactions between the B variant of κ-CN with AB of β-Lg and the combination of A κ-CN with AA of β-Lg for the total protein content, were found.     

Ultrastructural characteristics of the lung of <i>Melanophryniscus stelzneri stelzneri</i> (Weyenberg, 1875) (Anura,Bufonidae)

The lung of the toad, Melanophryniscus stelzneri stelzneri was studied using scanning and transmission electron microscopy. In M.s.stelzneri the parenchyma forms a polygonal network arrangement, therefore the parenchyma is edicular. These spaces are delimited by the interconnection of third order septa which are covered by respiratory epithelium. Small patches of ciliated epithelium without goblet cells appear irregularly distributed on the septa. The respiratory epithelium consists of one type of pneumocyte, which shows characteristics of both type I and type II alveolar cells of higher vertebrates. The pneumocytes are irregular in shape and possess attenuated cytoplasmic processes, which spread around the capillaries to form the outer layer of the air-blood barrier. These cells contain different types of cytoplasmic bodies: electron dense bodies, multivesicular bodies and lamellar bodies. Dense bodies are probably the precursors of lamellar bodies and the multivesicular bodies are incorporated into the latter. Neuroepithelial bodies appear randomly distributed over the septa. These bodies are separated from the lumen of the lung by thin cytoplasmic processes of neighbouring pneumocytes. The air-blood barrier consists of three layers: epithelium, interstitial space and endothelium.
The relatively simple pulmonary structure of M.s.stelzneri is due to a lower degree of partitioning of the pulmonary lumen in comparison to the lung of other bufonid anurans, could be correlated with a well developed cutaneous and buccopharingeal respiration. The testing of this hypothesis awaits further studies.     

Viability of microencapsulated Bifidobacterium animalis ssp. lactis BB12 in kefir during refrigerated storage

The viability of free and immobilized cells of Bifidobacterium animalis ssp. lactis BB12 incorporated into kefir was studied for 28 days during refrigerated storage. The immobilized bifidobacteria were added directly to previously prepared kefir. Titratable acidity, pH, ethanol, fat, protein and lactose were evaluated in the kefir with bifidobacteria after the storage. The survival of the free and microencapsulated bifidobacteria was evaluated during the storage period and in simulated gastric juice. The pH of kefirs ranged from 4.3 to 4.6. Encapsulation improved significantly the survival of bifidobacteria during exposure to nisin, during the storage period and in simulated gastric juice.     

Use of reconstituted concentrated nonfat milk for the production of UHT milk: physical and chemical effects and stability

The objective of this work was to evaluate the use of reconstituted concentrated nonfat milk for the production of UHT milk and to evaluate its physical and chemical effects and stability. The study considered three treatments related to the raw material and processing parameters. Increasing the intensity of thermal treatments resulted in increased hydroxymethylfurfural (HMF) content as well as the denaturation of whey protein. During storage, the milk that was produced from reconstituted concentrate displayed a lesser degree of proteolysis and higher pH value, sedimentation index and HMF, compared to natural milk. Under higher storage temperatures, the degree of proteolysis, HMF and pH decreased and the sedimentation index increased.     

INHIBITION OF LISTERIA MONOCYTOGENES BY CARNOBACTERIUM PISCICOLA IN VACUUM-PACKAGED COOKED CHICKEN AT REFRIGERATION TEMPERATURES

Listeria monocytogenes inhibition by bacteriocinogenic Carnobacterium piscicola DX or nonbacteriocinogenic C. piscicola 2818 was examined in vacuum-packed minimally processed chicken cubes with gravy at 4, 8 and 15C. C. piscicola DX and C. piscicola 2818 at 10⁴ CFU/g were coinoculated individually with a pool of three Listeria monocytogenes strains at 10² CFU/g. At 4 and 8C , C. piscicola DX inhibited growth of L. monocytogenes by 3 logs, significantly (P < 0.05) more than did C. piscicola 2818. At 15C both C. piscicola strains inhibited L. monocytogenes by one log cycle. The pH of all inoculated systems decreased from an initial pH of 6.14 to final values ranging from 6.06 to 5.65 depending on the inocula used. Bacteriocin was detected in the systems coinoculated with C. piscicola DX. These studies demonstrate that lower temperatures and bacteriocin production enhanced L. monocytogenes inhibition by C. piscicola