Edith Ponce-Alquicira

Antioxidant effect rosemary (Rosmarinus officinalis L.) and oregano (Origanum vulgare L.) extracts on TBARS and colour of model raw pork batters

Herbs and spices are traditional used as food ingredients as well as for their antioxidant properties. The objective of this work was to study the concentration of carnosol, rosmarinic and carnosic acids in rosemary (Rosmarinus officinalis L.) and oregano leaves (Origanum vulgare L.), and their effect on the oxidation and colour of model pork batters. Extracts were obtained by maceration with ethanol and reflux with chloroform. Rosemary extracts showed higher antioxidant activity, even more than the phenol compounds separately. These extracts also showed the highest antioxidant capacity, possibly due to the presence of high concentrations of carnosic acid and carnosol and unidentified active compounds. However, ethanol oregano extracts containing high concentrations of phenols, mainly rosmarinic acid, efficiently prevented colour deterioration. The antioxidant effect of the studied extracts depends, not only on the concentration of phenol compounds (rosmarinic acid, carnosol and carnosic acid), but also on the extraction method and solvent.

Biochemical characterization of a bacteriocin-like inhibitory substance produced by Enterococcus faecium MXVK29, isolated from Mexican traditional sausage

BACKGROUND Enterococci are lactic acid bacteria that can produce bacteriocins, which may offer an additional hurdle to control the growth of food-borne pathogens; moreover, these bacteriocins may have great potential as natural biopreservatives. The aim of this work was to characterize a bacteriocin-like inhibitory substance (BLIS) with antilisterial activity produced by an enterococcal strain. RESULTS The bacteriogenic strain was isolated from Mexican fermented sausages and identified as Enterococcus faecium with 99% sequence similarity. Maximal activity was detected at 16 h, where bacterial growth was in middle of the stationary phase. The producer strain was not inhibited by its own antimicrobial peptide. BLIS showed a strong anti-Listeria activity and was inactivated by proteinase K. Heating (121 °C for 15 min) induced some inactivation, but thermotolerance was higher at acid pH values. The yield obtained with a pH-mediated purification process was 32.7%, showing a band with an estimated molecular weight of 3.5 kDa. Automated N-terminal Edman degradation showed the following sequence: YYGNGVTCGSHHCSVD. CONCLUSION Biochemical characteristics of BLIS produced by E. faecium MXVK29 suggested that it belongs to Class IIa of the Klaenhammer classification and could be considered as a natural food preservative, although further studies need to be performed.

Histamine Production by Two Enterobacteriaceae Strains Isolated from Tuna (Thunnus thynnus) and Jack Mackerel (Trachurus murphyii)

Abstract Growth of Enterobacteriaceae in scombroids such as tuna (Thunnus thynnus) and jack mackerel (Trachurus murphyii) usually promotes aminoacid decarboxylation to biogenic amines. Among these compounds, histamine, produced by histidin-decarboxylase activity, is reported as toxic. The objective of this study was to compare histamine production by a strain, identified as Serratia liquefaciens, isolated from tuna (T. thynnus) caught in the Gulf of Mexico and Morganella morganii isolated from Chilean jack mackerel (T. murphyii). Morganella morganii had higher histamine producing ability in a synthetic medium than S. liquefaciens, presumably as a result of stressing conditions on M. morganii. However, in a medium formulated with muscle protein extracts obtained from tuna S. liquefaciens showed higher histamine production at similar microbial counts. In this medium, histidine was extracted together with proteins from tuna striated muscle, it was assumed that it acted as histamine production promoter.

Proteolytic and Lipolytic Changes in Beef Inoculated with Spoilage Microorganisms and Bioprotective Lactic Acid Bacteria

Abstract The use of a controlled lactic fermentation has been studied by several authors as a means to extend meat shelf‐life without notably altering its sensory quality. Growth and metabolite production by spoilage microorganisms as well as by bioprotective strains are influenced by storage conditions. The objective of this work was to study the effect of temperature and storage time upon the growth and metabolite production of four spoilage bacteria and three bioprotective lactic acid strains in vacuum packaged, finely cut beef. Lipolysis was mainly due to the presence of Brochothrix thermosphacta at 4°C and at 20°C, whereas proteolysis was mainly caused by pseudomonads. Presence of Lactobacillus minor, a heterofermentative strain, did not promote proteolysis nor lipolysis at either temperature. No considerable lipolysis was observed until day 8 of storage in samples inoculated with bioprotective strains, but increased at day 12 when stored at 20°C; no proteolysis was observed at any storage temperature.

Changes in the physicochemical and sensory characteristics in raw and grilled ovine meat

BACKGROUND The effect of storage time on sensory attributes and physicochemical characteristics (pH, L*, a*, b* color parameters, protein solubility, Warner-Bratzler shear force (WBSF), texture profile analysis (TPA), proteolytic activity, moisture and peptide changes) were evaluated as indicators of ovine meat quality changes during refrigeration. Meat samples were stored for 14 days at 2 ± 1 °C. The samples were divided into two sections: one was analyzed raw and the other was grilled to 72 ± 2 °C prior to analysis. The data were examined using multivariate data analysis (principal component analysis). RESULTS Tenderness showed a positive relationship with pH (0.55), and brightness presented a high correlation with sarcoplasmic protein solubility (-0.83) and L* (0.85) in raw ovine meat. Variations during storage were observed; for instance, textural parameters had a maximum value on the third day of storage for raw and grilled meat and decreased over the following days. Conversely, days 7 and 14 were distinguished by higher L* and b* values and by a greasy and bloody odor in the raw ovine meat. On day 14, grilled meat was characterized by chewiness on TPA, an intense grilled-meat odor and intense flavor, which had a positive relationship with cytochrome c equivalents (0.89). Likewise, sensory hardness was highly correlated with WBSF in grilled meat (0.89). CONCLUSION This information may be useful for describing and predicting ovine meat quality for both consumers and processors. Therefore, vacuum-packaged ovine meat can be stored for 14 days without disagreeable color to the consumer, and the raw meat texture is tender.

Release of Five Indicator Volatiles from a Model Meat Emulsion to Study Phase Contribution to Meat Aroma

The objective of this work was to develop a model meat emulsion in order to study the release of aroma-related compounds from the lipid and aqueous phases. Hexanal, octanal and nonanal were taken as indicators of lipid oxidation whereas 2-ethyl-3,5-dimethyl pyrazine and 2-methyl pyrazine were Maillard reaction indicators. Four systems were studied: I) a model meat emulsion; II) phosphate buffer; III) phosphate buffer + myofibrillar proteins; and IV) canola oil. Release of indicator compounds from each of the studied systems was analyzed in the headspace. It was concluded that pyrazines mainly contributed to aroma in lipid systems and in protein solutions but not in emulsions and non protein aqueous systems. Hexanal, octanal, and nonanal were minor aroma contributors in lipid media, whereas hexanal and nonanal were released in small amount from protein emulsions. Conversely, octanal can be considered of an important aroma contributor in emulsions; the three aldehydes showed a high release from aqueous systems, with and without protein.

Evaluation of the Antioxidant Activity of Aqueous and Methanol Extracts of Pleurotus ostreatus in Different Growth Stages.

Total polyphenols and flavonoids contents, as well as ferric reducing antioxidant power (FRAP), metal ions chelating activity, reducing power assay and scavenging activity of DPPH and ABTS radicals in aqueous and methanolic extracts obtained from mycelium, primordium, and fruiting body of Pleurotus ostreatus in both fresh as dry, were evaluated. The total polyphenol content of dried samples was higher in aqueous extracts obtained both in room temperature and boiling. The total polyphenol content of the fresh samples obtained at room temperature and boiling was higher in aqueous extract of mycelium and in the methanolic extract of the fruiting body. In general, flavonoids represented a very small percentage of the total polyphenol content. The antioxidant activity measured by the FRAP method of extracts from fresh samples were higher with respect to the dried samples. The results of the metal ion chelating activity indicate that all extracts tested had acted. The reducing power of all samples was concentration dependent. In general, the extracts of dried samples showed higher reducing power than the extracts of fresh samples and tend to show greater reducing power by aqueous than methanolic extracts. It was observed that the DPPH and ABTS radical scavenging activities were positively correlated to the concentration of the extract. The results suggested that antioxidant activity could be due to polyphenols, but mainly by different molecules or substances present in the extracts. Overall, the fruiting body of P. ostreatus showed the best results and the possibility of continuing to investigate its functional properties of this fungus is opened. This is the first report where the antioxidant activity of P. ostreatus in different growth stage was reported.

Effect of Extrinsic Parameters on the Production of a Bacteriocin by Lactobacillus buchneri, Isolated from Mexican Raw Sausages

Bacteriocins are antimicrobial peptides acting on certain pathogens and spoilage microorganisms. They have recently been considered as natural alternative to food preservatives. The objective of this work was to study the inhibition spectrum of a bacteriocin produced by Lactobacillus buchneri, isolated from a Mexican sausage, against Listeria monocytogenes and several lactic acid bacteria, and the influence of several extrinsic parameters on bacteriocin activity. Culture media (MRS or APT) had no significant effect on bacteriocin production (p < 0.060) although higher activity was observed in MRS (220 AU/mL). Conversely, temperature significant affected production (p > 0.001). Bacteriocin activity was also increased by 100% nitrogen atmosphere (180 AU/mL) as compared to N2/CO2 (50:50) (150 AU/mL) and 100% CO2 (60 AU/mL). Maximum activity occurred at the end of the exponential growth phase. This bacteriocin inhibited some Listeria monocytogens strains and several lactic acid bacteria, mainly Lactobacillus sp.

Quality traits of pork semimembranosus and triceps brachii muscles sourced from the United States and Mexico.

The study included fresh pork semimembranosus (SM, n=289) and triceps brachii (TB, n=283) muscles sourced from meat packers of Mexico and the USA. Samples were analyzed for moisture, protein, and fat content, pH, shear force (WBSF), cook loss, water holding capacity (WHC), instrumental color, emulsion capacity (EC) and stability (ES), and consumer sensory ratings. SM from the USA had lower WBSF (P<0.05) than that from Mexico (26.7 vs. 29.7N), higher WHC (44.7 vs. 38.4%; P<0.05) and a better appearance, as indicated by its lower h* (52.3 vs. 56.6; P<0.05) and higher C* (23.1 vs. 21.3; P<0.05). Consumer acceptance of SM was similar (P>0.05) across countries. TB from Mexico had higher (P<0.05) fat content (2.5 vs. 2.0%), lower (P<0.05) WBSF values (32.0 vs. 36.9N), and received more positive ratings by Mexican consumers (87.1 vs. 81.7%) than its US equivalent. In general, US pork exhibits better technological properties, while country of origin has less effect on consumer acceptability.

Integral Use of Amaranth Starch to Obtain Cyclodextrin Glycosyltransferase, by Bacillus megaterium, to Produce β-Cyclodextrin

Cyclodextrin glycosyltransferase (CGTase) is an enzyme that produces cyclodextrins (CDs) from starch and related carbohydrates, producing a mixture of α-, β-, and γ-CDs in different amounts. CGTase production, mainly by Bacillus sp., depends on fermentation conditions such as pH, temperature, concentration of nutrients, carbon and nitrogen sources, among others. Bacillus megaterium CGTase produces those three types of CDs, however, β-CD should prevail. Although, waxy corn starch (CS) is used industrially to obtain CGTase and CDs because of its high amylopectin content, alternative sources such as amaranth starch (AS) could be used to accomplish those purposes. AS has high susceptibility to the amylolytic activity of CGTase because of its 80% amylopectin content. Therefore, the aim of this work was evaluate the AS as carbon source for CGTase production by B. megaterium in a submerged fermentation. Afterwards, the CGTase was purified partially and its activity to synthesize α-, β-, and γ-CDs was evaluated using 1% AS as substrate. B. megaterium produced a 66 kDa CGTase (Topt = 50°C; pHopt = 8.0), from the early exponential growth phase which lasted 36 h. The maximum CGTase specific activity (106.62 ± 8.33 U/mg protein) was obtained after 36 h of culture. CGTase obtained with a Km = 0.152 mM and a Vmax = 13.4 μM/min yielded 40.47% total CDs using AS which was roughly twice as much as that of corn starch (CS; 24.48%). High costs to produce CDs in the pharmaceutical and food industries might be reduced by using AS because of its higher α-, β- and γ-CDs production (12.81, 17.94, and 9.92%, respectively) in a shorter time than that needed for CS.