Resistance of Vigna unguiculata (cowpea) seeds to Callosobruchus maculatus is restricted to cotyledonary tissues

We have investigated the survival of Callosobruchus maculatus larvae when reared on resistant IT81D 1045 Vigna unguiculata seeds, whose resistance has been associated with variant forms of vicilins. Here, we present data which show that larvae of C. maculatus feeding on embryonic axis of resistant cowpea reach a mass of around 28 times higher than those feeding on cotyledonary tissues. Additionally, incorporation of 5–10% of embryonic axis flour on artificial seeds made of resistant flour restores toxicity of seeds to the bruchid. Vicilins purified from both susceptible and resistant embryonic axis had no deleterious effects either on insect development or on insect survival until a level of 4% of incorporation. In contrast, vicilins from resistant cotyledons show an LD₅₀ (50% lethal dose) and WD₅₀ (half weight dose) of 2%. Total vicilin contents of embryonic axes were around two times lower than in cotyledonary tissues, while proteolytic activities of all four proteinase classes were always higher in the former tissues. By 2D‐PAGE we visualized eight protein spots, which seem to be exclusively found on resistant cotyledons. Copyright © 2006 Society of Chemical Industry     

The effect of the research setting on the emotional and sensory profiling under blind,expected, and informed conditions: A study on premium and private label yogurt products

Although sensory and emotional evaluation of food products mostly occurs in a controlled laboratory environment, it is often criticized as it may not reflect a realistic situation for consumers. Moreover, products are mainly blind evaluated by participants, whereas external factors such as brand are often considered as key drivers of food choice. This study aims to examine the role of research setting (central location test versus home-use test) and brand information on the overall acceptance, and sensory and emotional profiling of 5 strawberry-flavored yogurts. Thereby, private label and premium brands are compared under 3 conditions: blind, expected, and informed (brand information). A total of 99 adult subjects participated in 3 sessions over 3 consecutive weeks. Results showed that overall liking for 2 yogurt samples was higher in the laboratory environment under the informed evaluation condition, whereas no effect of research setting was found under the blind and expected conditions. Although emotional profiles of the products differed depending on the research setting, this was less the case for the sensory profiles. Furthermore, brand information clearly affected the sensory perception of certain attributes but had less influence on overall liking and emotional profiling. These results indicate that both scientists and food companies should consider the effect of the chosen methodology on ecological validity when conducting sensory research with consumers because the laboratory context could lead to a more positive evaluation compared with a home-use test.     

Proteolysis in model Portuguese cheeses: Effects of rennet and starter culture

To shed further light onto the mechanisms of proteolysis that prevail throughout ripening of Portuguese cheeses, model cheeses were manufactured from bovine milk, following as much as possible traditional manufacture practices – using either animal or plant rennet. The individual role upon proteolysis of two (wild) strains of lactic acid bacteria – viz. Lactococcus lactis and Lactobacillus brevis, which are normally found to high viable numbers in said cheeses, was also considered, either as single or mixed cultures. Our experimental results confirmed the influence of rennet on the proteolysis extent, but not on proteolysis depth. On the other hand, the aforementioned strains clearly improved release of medium- and small-sized peptides, and contributed as well to the free amino acid pool in cheese.     

Use of mild irradiation doses to control pathogenic bacteria on meat trimmings for production of patties aiming at provoking minimal changes in quality attributes

The objectives of the present work were to assess the use of moderate doses of gamma irradiation (2 to 5 kGy) and to reduce the risk of pathogen presence without altering the quality attributes of bovine trimmings and of patties made of irradiated trimmings. Microbiological indicators (coliforms, Pseudomonas spp and mesophilic aerobic counts), physicochemical indicators (pH, color and tiobarbituric acid) and sensory changes were evaluated during storage. 5 kGy irradiation doses slightly increased off flavors in patties. Two pathogenic markers (Listeria monocytogenes and Escherichia coli O157:H7) were inoculated at high or low loads to trimming samples which were subsequently irradiated and lethality curves were obtained. Provided that using irradiation doses ≤ 2.5 kGy are used, reductions of 2 log CFU/g of L. monocytogenes and 5 log CFU/g of E. coli O157:H7 are expected. It seems reasonable to suppose that irradiation can be successfully employed to improve the safety of frozen trimmings when initial pathogenic bacteria burdens are not extremely high.     

Heat stress affects some physiological and productive variables and alters metabolism in dairy ewes

Heat stress (HS) has a significant economic impact on the global dairy industry. However, the mechanisms by which HS negatively affects metabolism and milk synthesis in dairy ewes are not well defined. This study evaluated the production and metabolic variables in dairy ewes under controlled HS conditions. Eight Lacaune ewes (75.5 ± 3.2 kg of body weight; 165 ± 4 d of lactation; 2.31 ± 0.04 kg of milk per day) were submitted to thermoneutral (TN) or HS conditions in a crossover design (2 periods, 21 d each, 6-d transition). Conditions (day-night, 12–12 h; relative humidity; temperature-humidity index, THI) were: TN (15–20°C; 50 ± 5%; THI = 59–65) and HS (28–35°C; 45 ± 5%; THI = 75–83). Ewes were fed ad libitum and milked twice daily. Rectal temperature, respiratory rate, feed intake, water consumption, and milk yield were recorded daily. Milk and blood samples were collected weekly. Additionally, TN and HS ewes were exposed to glucose tolerance test, insulin tolerance test, and epinephrine challenge. Heat stress reduced feed intake (?11%), and increased rectal temperature (+0.77°C), respiratory rate (+90 breaths/min), and water consumption (+28%). Despite the reduced feed intake, HS ewes produced similar milk to TN ewes, but their milk contained lower fat (?1.7 points) and protein (?0.86 points). Further, HS milk tended to contain more somatic cells (+0.23 log points). Blood creatinine was greater in HS compared with TN, but no differences in blood glucose, nonesterified fatty acids, or urea were detected. When glucose was infused, TN and HS had similar insulin response, but higher glucose response (+85%) was detected in HS ewes. Epinephrine infusion resulted in lower nonesterified fatty acids response (?215%) in HS than TN ewes. Overall, HS decreased feed intake, but milk production was not affected. Heat stress caused metabolic adaptations that included increased body muscle degradation and reduced adipose tissue mobilization. These adaptations allowed ewes to spare glucose and to avoid reductions in milk yield.     

Effect of different levels of CO2 on the antioxidant content and the polyphenol oxidase activity of ‘Rocha’ pears during cold storage

Pears (Pyrus communis L. cv. ‘Rocha’) were exposed to air or controlled atmosphere (CA) containing various concentrations of CO₂: 0, 0.5 and 5 kPa, all with 2 kPa O₂. After 4 months of storage at 2 °C, the fruits were transferred to air at room temperature, and assessed in terms of soluble solids, titratable acidity, pH, incidence of brown heart and flesh browning, phenolic content, vitamin C content and polyphenol oxidase activity. By 4 months of storage, soluble solids and pH increased, and acidity decreased relative to harvest, but no differences were detected between pears stored under air or any of the CA tested. Higher contents of hydroxycinnamic derivatives and flavan‐3‐ols in the peel than in the flesh were recorded. However, the content of arbutin was higher in the flesh than in the peel, whereas flavonols were only detected in the peel. In general, hydroxycinnamic derivatives and flavonols were stable throughout storage, but flavan‐3‐ols decreased in concentration under air or CA. Arbutin was the only phenolic compound that increased in concentration as time elapsed. No clear relation was found between the storage conditions tested and the phenolic concentration in pears. Regarding ascorbic acid (AA) and dehydroascorbic acid (DHA), their concentrations were higher in the peel than in the flesh. Furthermore, AA and DHA were strongly affected by storage: the former decreased, whereas the latter increased in content. A decrease in PPO activity was apparent after harvest and during storage, particularly under higher levels of CO₂. The combination 2 kPa O₂ + 5 kPa CO₂ increased the incidence of internal disorders (viz. brown heart and flesh browning) after storage. Copyright © 2005 Society of Chemical Industry     

Assessment of safety of enterococci isolated throughout traditional Terrincho cheesemaking: virulence factors and antibiotic susceptibility

Enterococci account for an important fraction of the adventitious microflora of traditional cheeses manufactured in Mediterranean countries from small ruminants' raw milk and play an important role in the development of suitable organoleptic characteristics of the final product. It has been suggested that animals used for food or animals that supply edible products are a reservoir of antibiotic-resistant enterococci. The main purpose of this research effort was thus to identify, to the species level, a total of 73 enterococci with high tolerance to acidic pH and bile salts (as prevailing environmental conditions in the first portion of the gastrointestinal tract), which were previously isolated from the milk feedstock to the final product of Terrincho cheesemaking, and to determine their profiles of antibiotic susceptibility, coupled with the occurrence of specific virulence factors (especially in those that might eventually be claimed to exhibit suitable probiotic and technological performances). Isolates, identified by both API 20 STREP and PCR methods, were found to belong to the following Enterococcus species: E. casseliflavus, E. durans, E. faecalis, E. faecium, and E. gallinarum. Susceptibility of those isolates was observed to most antibiotics tested, whereas none harbored aminoglycoside resistance genes. PCR screenings for cytolysin genes (cylL(L), cylL(s), cylM, cylB, and cylA), surface adhesin genes (efaA(fs), efaA(fm), and esp), the aggregation protein gene (agg), and the extracellular metalloendopeptidase gene (gelE) were performed. All isolates proved negative for cylL(L), cylM, cylB, and agg genes. Both E. faecalis strains were positive for the cell wall-associated protein Esp and the cell wall adhesin efaA(fs), whereas the cell wall adhesin efaA(fm) was detected in 11 of the 12 E. faecium strains. Only one strain possessed the cylL(s) determinant, and another possessed the cylA gene. Incidence of virulence determinants was thus very low; hence, the enterococcal adventitious microflora tested is essentially safe.