Thirty-three Chilean corn accessions were screened for the first time regarding their phenolic profiles, total phenolic contents (TPC), antioxidant capacity (DPPH and ABTS), and in vitro inhibition against key enzymes relevant for hyperglycemia (α-amylase and α-glucosidase) and hypertension (angiotensin I-converting enzyme, ACE-I) in both free and cell wall-bound fractions. TPC varied from 132.2 to 262.5 mg of gallic acid equivalents/100g dry weight (DW), and around 88% of TPC and antioxidant capacity were found in the bound form. Vanillin, vanillic, protocatechuic, ferulic, and p-coumaric acids were detected by HPLC in free fractions, whereas ferulic and p-coumaric acids were found in the bound form. Pisankalla accession (red kernel) had the highest ferulic acid content (269.5 mg/100g DW). No α-amylase and ACE-I inhibition were found; however, all free fractions inhibited α-glucosidase (10.8-72.5%). Principal component analysis revealed that darker samples (free fraction) showed higher TPC and antioxidant capacity, while α-glucosidase inhibition was related to yellow-colored samples.

(2013) Phenolic compounds, antioxidant capacity, and invitro α-amylase inhibitory potential of tea infusions (Camelliasinensis) commercialized in Chile, CyTA -Journal of Food, 11:1, 60-67, DOI: 10.1080/19476337.2012 To link to this article: https://doi.org/10. 1080/19476337.2012 Chile is considered the largest tea consumer in America, so a broad variety of tea types and brands are available in Chilean markets. Thirty-four commercial teas (white, green, red, oolong, and black) commonly found in Chile were evaluated according to their phenolic profiles, antioxidant capacity, and in vitro inhibition against a-amylase relevant for hyperglycemia control. Multivariate tools were used to evidence patterns among samples respect their biochemical parameters. Green and white tea groups showed higher total phenolic contents than red and black teas. All tea samples inhibited the 2,2-diphenyl-1-picrylhydrazyl free radical and black teas significantly inhibited the a-amylase enzyme. Major phenolics detected by liquid chromatography in green and white teas were epigallocatechingallate and epicatechingallate, whereas gallic acid was common in black, red, and oolong teas. Caffeine was found across all samples. The multivariate analysis evidenced a high variability among analyzed tea and even from brand to brand.Keywords: Camellia sinensis; phenolics; free radical inhibition; a-amylase inhibition Chile es considerado el mayor consumidor de te´en Ame´rica y una amplia variedad en tipos y marcas de te´existen en el mercado chileno. Un total de treinta y cuatro muestras de te´(blanco, verde, rojo, oolong y negro) fueron evaluadas de acuerdo a sus perfiles de compuestos feno´licos, capacidad antioxidante e inhibicio´n in vitro de la a-amilasa, relevante en el control de la hiperglicemia. Se utilizaron herramientas multivariantes para evidenciar patrones entre las muestras respecto a sus para´metros bioquı´micos. Los grupos de te´verdes y blancos presentaron los valores ma´s altos en feno´licos totales. Todas las muestras inhibieron el radical libre 2,2-difenil-1-picrilhidracilo, en cambio so´lo los te´s negros inhibieron significativamente la enzima a-amilasa. Los principales compuestos feno´licos detectados por cromatografı´a lı´quida en te´verde y blanco fueron la epigalocatequina-galato y epicatequinagalato, mientras que a´cido ga´lico fue detectado en las muestras de te´negro, rojo y oolong. Se detecto´cafeı´na en todas las muestras evaluadas. El ana´lisis multivariante demostro´una alta variabilidad entre las muestras de te´y aú n entre las diferentes marcas procedentes de un mismo tipo de te´.

Listeria monocytogenes is a foodborne pathogen that can cause severe disease in susceptible humans. This microorganism has the ability to adapt to hostile environmental conditions such as the low temperatures used by the food industry for controlling microorganisms. Bacteria are able to adjust their transcriptional response to adapt to stressful conditions in order to maintain cell homeostasis. Understanding the transcriptional response of L. monocytogenes to stressing conditions could be relevant to develop new strategies to control the pathogen. A possible alternative for controlling microorganisms in the food industry could be to use copper as an antimicrobial agent. The present study characterized three L. monocytogenes strains (List2-2, Apa13-2, and Al152-2A) adapted to low temperature and challenged with different copper concentrations. Similar MIC-Cu values were observed among studied strains, but growth kinetic parameters revealed that strain List2-2 was the least affected by the presence of copper at 8°C. This strain was selected for a global transcriptional response study after a 1 h exposition to 0.5 mM of CuSO 4 × 5H 2 O at 8 and 37°C. The results showed that L. monocytogenes apparently decreases its metabolism in response to copper, and this reduction is greater at 8°C than at 37°C. The most affected metabolic pathways were carbohydrates, lipids and nucleotides synthesis. Finally, 15 genes were selected to evaluate the conservation of the transcriptional response in the other two strains. Results indicated that only genes related to copper homeostasis showed a high degree of conservation between the strains studied, suggesting that a low number of genes is implicated in the response to copper stress in L. monocytogenes . These results contribute to the understanding of the molecular mechanisms used by bacteria to overcome a combination of stresses. This study concluded that the application of copper in low concentrations in cold environments may help to control foodborne pathogens as L. monocytogenes in the industry.

The capacity to grow at low temperatures has allowed Listeria monocytogenes to become one of the primary food pathogens to date, representing a major public health problem worldwide. Several works have described the homeostatic response of L. monocytogenes under different copper (Cu) treatments growing at mild temperature (30 °C). The aims of this report were to evaluate if changes in the external concentration of Cu affected viability and Cu homeostasis of L. monocytogenes growing at low temperature. Ours results showed that L. monocytogenes growing at 8 °C had a reduced viability relative to 30 °C when exposed to Cu treatments. This decrease was correlated with an increase in the internal concentration of Cu, probably linked to the transcriptional down-regulation of mechanisms involved in Cu homeostasis. This combined effect of Cu and low temperature showed a synergistic impact over the viability and homeostasis of L. monocytogenes, where low temperature exacerbated the toxic effect of Cu. These results can be useful in terms of the use of Cu as an antibacterial agent.

In this study, we focused on the effect of an enterocin or an Enterococcus faecalis strain added onto sliced dry-cured ham that was artificially inoculated with Listeria monocytogenes and stored at 7°C. The population of L. monocytogenes and the expression of five genes were monitored throughout the storage period. A persistent and a nonpersistent strain were tested, and both were influenced by the presence of the enterocin; both populations were reduced by more than 2 Log CFU/g after 14 days compared with the control, noninoculated ham. The presence of E. faecalis, a bacteriocin-producing lactic acid bacterium, had a less pronounced effect on the viable counts for both strains. Concerning gene expression, a common trend observed for both strains in the presence of enterocin was the down-regulation of genes tested after 30 min of storage at 7°C. For the remainder of the storage period, the expression fluctuated but was mostly reduced. Similarly, the presence of E. faecalis led to an overall down-regulation of genes. The effect on gene expression of both enterocin and E. faecalis was more pronounced on the nonpersistent L. monocytogenes strain. Although the potential of a bacteriocin and a bacteriocin-producing microorganism to control L. monocytogenes was confirmed, this study highlights that gene expression may be influenced and needs to be evaluated when considering such biopreservation interventions.