We examined the relative function of the two classes of guanine nucleotide exchange factors (GEFs) for ADP-ribosylation factors that regulate recruitment of coat proteins on the Golgi complex. Complementary overexpression and RNA-based knockdown approaches established that GBF1 regulates COPI recruitment on cis-Golgi compartments, whereas BIGs appear specialized for adaptor proteins on the trans-Golgi. Knockdown of GBF1 and/or COPI did not prevent export of VSVGtsO45 from the endoplasmic reticulum (ER), but caused its accumulation into peripheral vesiculotubular clusters. In contrast, knockdown of BIG1 and BIG2 caused loss of clathrin adaptor proteins and redistribution of several TGN markers, but had no impact on COPI and several Golgi markers. Surprisingly, brefeldin A-inhibited guanine nucleotide exchange factors (BIGs) knockdown prevented neither traffic of VSVGtsO45 to the plasma membrane nor assembly of a polarized Golgi stack. Our observations indicate that COPII is the only coat required for sorting and export from the ER exit sites, whereas GBF1 but not BIGs, is required for COPI recruitment, Golgi subcompartmentalization, and cargo progression to the cell surface.

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Corn starches were isolated using three different methods: water steeping, alkaline steeping, and acid steeping. The effects on their structural, micro structural, thermal, and chemical properties were evaluated, with especial emphasis in the alkaline process that is close related to the nixtamalization process. The isolation method influences the amylose content, crystallinity, and enthalpy of the starch granules. Scanning electron microscopy showed that the isolation method produced changes on the surface of the granules, and in some cases there were holes on the surface. Method 2 (the alkaline method) produces the starch granules with low protein and fat content and there was an increase in the enthalpy for this method, that can be explained in terms of thermodynamics by the increase of particles into the starch granules, which was confirmed by an increase in the ash content. A negative correlation between these variables was found (r ¼ 70.99), while a positive correlation between enthalpy and amylose content was also found (r ¼ 1).Keywords: corn starch; isolation method; functional properties of starch; amylose; amylopectin Almidones de maı´z fueron aislados por tres diferentes me´todos: usando reposo en agua, reposo alcalino y reposo a´cido. Se evaluaron los efectos de estos me´todos sobre las propiedades estructurales, microestructurales, te´rmicas y quı´micas en los gra´nulos de almido´n. Los resultados mostraron que los me´todos de obtencio´n de almido´n tienen fuerte influencia en el contenido de amilosa en los almidones aislados, ası´como en su estructura cristalina obtenida mediante difraccio´n de rayos X, ası´como cambios en la superficie de los gra´nulos observados por microscopia electro´nica de barrido, se tiene especial e´nfasis en el proceso alcalino, por que es cercano al proceso de nixtamalizacion. El me´todo alcalino produjo gra´nulos de almido´n con bajo contenido de proteı´na y grasa. En el caso del tratamiento alcalino, en te´rminos termodina´micos, el incremento en la entalpia tambie´n puede ser explicado por el incremento de las partı´culas dentro de los gra´nulos de almido´n, resultado que es confirmado por el incremento del contenido de cenizas. Finalmente, se encontro´una correlacio´n (r ¼ 70,99) tomando en cuenta los valores de cristalinidad y entalpia, y una correlacio´n positiva (r ¼ 1) entre entalpia y contenido de amilosa.Palabras clave: almido´n de maı´z; me´todo de aislamiento; propiedades funcionales de almido´n; amilosa; amilopectina

Handcrafted fresh cheeses are popular among consumers in Mexico. However, unsafe raw materials and inadequate food safety practices during cheese manufacture and preservation make them a potential public health risk. The incidence of Salmonella, Listeria, Escherichia coli O157:H7, and staphylococcal enterotoxin was analyzed in two types of fresh cheese (panela and adobera) commonly marketed in Mexico. A total of 200 samples, 100 panela and 100 adobera, were acquired from 100 wholesale milk product distributors who supply small retailers in the Guadalajara metropolitan area, Jalisco State, Mexico. Pathogens were identified using culture and immunoassay (miniVidas) methods. The presence of staphylococcal enterotoxin was determined by an immunoassay method. Of the 200 analyzed samples, 92 were positive for at least one of the pathogens. The incidence in the panela samples was 56%: 34% Salmonella, 16% E. coli O157:H7, and 6% L. monocytogenes. In the adobera samples, incidence was 36%: 20% Salmonella, 4% E. coli O157:H7, and 12% L. monocytogenes. Staphylococcal enterotoxin was not detected in any of the 200 samples. Choice of technique had no effect on detection of pathogen incidence, although the immunoassay method identified more Salmonella serotypes than the culture method. Handcrafted panela and adobera fresh cheeses in Mexico frequently contain pathogenic bacteria and therefore pose a public health risk.

Roselle (Hibiscus sabdariffa L.), also known as jamaica in Spanish, is a perennial plant that grows in tropical and subtropical regions, including China, Egypt, Indonesia, Mexico, Nigeria, Thailand, and Saudi Arabia. It has a long history of uses, mainly focused on culinary, botanical, floral, cosmetic, and medicinal uses. The latter being of great impact due to the diuretic, choleretic, analgesic, antitussive, antihypertensive, antimicrobial, immunomodulatory, hepatoprotective, antioxidant, and anti-cancer effects. These therapeutic properties have been attributed to the bioactive compounds of the plant, mainly phenolic acids, flavonoids, anthocyanins, and organic acids (citric, hydroxycitric, hibiscus, tartaric, malic, and ascorbic). Most literature reviews and meta-analyses on the therapeutic potential of Hibiscus sabdariffa L. (Hs) compounds have not adequately addressed the contributions of its organic acids present in the Hs extracts. This review compiles information from published research (in vitro, in vivo, and clinical studies) on demonstrated pharmacological properties of organic acids found in Hs. The intent is to encourage and aid researchers to expand their studies on the pharmacologic and therapeutic effects of Hs to include assessments of the organic acid components.

A mixture of orange vesicle flour, commercial nixtamalized corn flour and potato starch was extruded using a Brabender Laboratory single screw extruder (2:1 L/D). The resulting pellets were expanded by microwaves. Expansion index, bulk density, penetration force, carotenoid content, and dietary fiber were measured for this third-generation snack and optimum production conditions were estimated. Response surface methodology was applied using a central composite rotatable experimental design to evaluate the effect of moisture content and extrusion temperature. Temperature mainly affected the expansion index, bulk density and penetration force, while carotenoids content was affected by moisture content. Surface overlap was used to identify optimum processing conditions: temperature: 128-130°C; moisture content: 22-24 %. Insoluble dietary fiber decreased and soluble dietary fiber increased after extrusion.

The presence of multidrug-resistant pathogenic bacteria in food is a significant public health concern. Diarrheagenic Escherichia coli pathotypes (DEPs) are foodborne bacteria. In Mexico, DEPs have been associated with diarrheal illness. There is no information about the presence of multidrug-resistant DEPs on fresh vegetables and in cooked vegetable salads in Mexico. "Nopalitos" (Opuntia ficus-indica L.) is a Cactacea extensively used as a fresh green vegetable throughout Mexico. The presence of generic E. coli and multidrug-resistant DEPs on raw whole and cut nopalitos and in nopalitos salad samples was determined. One hundred raw whole nopalitos (without prickles) samples, 100 raw nopalitos cut into small square samples, and 100 cooked nopalitos salad samples were collected from markets. Generic E. coli was determined using the most probable number procedures. DEPs were identified using two multiplex polymerase chain reaction procedures. Susceptibility to 16 antibiotics was tested for the isolated DEP strains by standard test. Of the 100 whole nopalitos samples, 100 cut nopalitos samples, and 100 nopalitos salad samples, generic E. coli and DEPs were identified, respectively, in 80% and 10%, 74% and 10%, and 64% and 8%. Eighty-two DEP strains were isolated from positive nopalitos samples. The identified DEPs included Shiga toxin-producing E. coli (STEC), enteropathogenic E. coli (EPEC), and enterotoxigenic E. coli (ETEC). All isolated strains exhibited resistance to at least six antibiotics. To the best of our knowledge, this is the first report of the presence of multidrug-resistant and antibiotic resistance profiles of STEC, ETEC, and EPEC on raw nopalitos and in nopalitos salads in Mexico.

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