Moisture migration in a cereal composite food at high water activity: Effects of initial porosity and fat content

2006 ◽  
Vol 43 (2) ◽  
pp. 144-151 ◽  
Author(s):  
Elisabeth Roca ◽  
Valérie Guillard ◽  
Stéphane Guilbert ◽  
Nathalie Gontard
Keyword(s):  
Water Activity ◽  
High Water ◽  
Fat Content ◽  
Initial Porosity ◽  
Moisture Migration

Occurrence of Toxigenic Molds in Brazilian Cheese

1992 ◽  
Vol 55 (3) ◽  
pp. 187-191 ◽  
Author(s):  
MARTA HIROMI TANIWAKI ◽  
ARIENE GIMENES FERNANDES VAN DENDER
Keyword(s):  
Water Activity ◽  
High Water ◽  
Penicillium Species ◽  
High Carbohydrate ◽  
Different Types ◽  
Carbohydrate Contents

Several samples of cheese obtained from regular retailers in Campinas, Brazil, were examined for molds and mycotoxins. Strains of Aspergillus and Penicillium were isolated and evaluated for their potential for producing toxins. Two of the isolated Penicillium species produced citrinin, while another produced patulin. However, no mycotoxins were detected in any of the cheese samples tested. Experiments with different types of cheese and a semisynthetic cheese were carried out in order to verify production of citrinin and patulin. It was observed that citrinin may be produced in cheese with high water activity and in semisynthetic cheese. However, patulin does not appear to be stable in cheese, even in semisynthetic cheese with high water activity and high carbohydrate contents.

Effects of vacuum and multiflash drying on the microbiota and colour of dried yellow mealworm (Tenebrio molitor)

2021 ◽  
pp. 1-12
Author(s):  
R.E.Y. Seho ◽  
R.L. Monteiro ◽  
J. De Dea Lindner ◽  
M. Miotto ◽  
B.A.M. Carciofi ◽  
...  
Keyword(s):  
Water Activity ◽  
Challenge Test ◽  
High Water ◽  
Tenebrio Molitor ◽  
Microbial Reduction ◽  
Microbial Load ◽  
Vacuum Drying ◽  
Drying Time ◽  
Yellow Mealworm ◽  
Food And Feed

Larvae of Tenebrio molitor (yellow mealworm; YM) are an alternative to conventional animal protein as food and feed thanks to their high nutritional value and low environmental impact for production. Since some studies have reported high water activity (aw) with different microbial contamination levels, blanching and drying can be employed to reduce microbial load, enzymatic activity, moisture content, and water activity, ensuring safety and preserving YM for longer periods. This study applied rinsing or blanching followed by vacuum- or multiflash drying, aiming to preserve YM by reducing aw and the microbial load, enabling its use as food and feed. The processing impact on YM colour was evaluated, and they were also subjected to an Escherichia coli contaminated wheat bran to perform a challenge test to evaluate the effectiveness of the decontamination. Drying curves were determined for each situation. Multiflash drying procedure was faster than vacuum drying for reducing YM moisture. Additionally, blanched samples required a shorter period to reach the targeted water activity (0.2-0.3) than rinsed samples. Blanching plus vacuum drying reduced more than 5 log E. coli load in YM in the challenge test. Vacuum drying preserved YM brightness the most. In conclusion, this study showed that drying could provide shelf-stable YM. Besides, only 15 s of blanching before drying gives better brightness and leads to a greater microbial reduction after a relatively short drying time.

Fermentation Problem in Spanish North-Coast Honey

1995 ◽  
Vol 58 (5) ◽  
pp. 515-518 ◽  
Author(s):  
SUSANA SANZ ◽  
GLORIA GRADILLAS ◽  
FUENCISLA JIMENO ◽  
CONSUELO PEREZ ◽  
TERESA JUAN
Keyword(s):  
Water Content ◽  
Water Activity ◽  
Microbiological Quality ◽  
Free Water ◽  
High Water ◽  
North Coast ◽  
High Water Content ◽  
Free Water Content ◽  
Cantabrian Coast ◽  
Mold And Yeast

Twenty-one samples from the Cantabrian coast were analyzed to establish their microbiological quality and fermentation tendency. In a food with a very low free-water content like honey, microbiological growth is only possible when there is an increase in water activity. Since most of the samples studied were not extensively granulated, the risk of fermentation is mostly due to high water content. Among our samples, only two had a water content below 17.1% (no risk of fermentation), whereas the high water activity of the rest of the samples indicates the possibility of microbial growth. In fact, four of the samples analyzed showed a moisture content over the Spanish maximum legal limit, which means a high risk of fermentation. The absence of Enterobacteriaceae, coliforms, and Escherichia coli in our samples indicates an appropriate cleanliness during extractions and handling of honey. No Salmonella or Shigella were found. The relationship between water activity and mold and yeast counts found for the honeys analyzed allowed us to divide our samples in two groups: honeys with a high or a low risk of fermentation. Changes observed during storage of the samples confirmed this classification.

Nutritional and Microbial Changes During Production of Tostones (Fried Plantains)

1981 ◽  
Vol 44 (1) ◽  
pp. 55-58
Author(s):  
R. J. ALVAREZ ◽  
J. A. KOBURGER ◽  
H. APPLEDORF
Keyword(s):  
Water Activity ◽  
Nutritional Quality ◽  
Fat Content ◽  
Moisture Loss ◽  
Crude Fiber ◽  
Penicillium Species ◽  
Large Segment ◽  
Zn Content ◽  
Salt Brine

Tostones (fried plantains) are consumed by a large segment of the Latin population in Florida. In addition, their use in specialty restaurants is on the increase. However, little is known about the microbial and nutritional quality of this product, particularly as affected by processing. Tostones are prepared by peeling and cutting the plantains into slices; soaking slices in a salt brine; frying, drying and flattening the slices; and refrying them until golden brown. Protein, ash, crude fiber and carbohydrate content increased during preparation as a result of moisture loss during processing. Fat content increased due to uptake during frying. Phosphorus, Na, Hg, Se and Zn content also increased, whereas that of K and Fe decreased. Changes in water activity and pH were not significantly pronounced. Bacillus and Penicillium species were the only organisms isolated from laboratory-prepared samples. The finished product contained 48.0% carbohydrate, 26.5% moisture, 21.5% fat, 2.5% protein, 1.0% ash, 0.5% crude fiber and 395 Kcal/100 g.

Survival of Salmonella enterica Serotype Tennessee during Simulated Gastric Passage Is Improved by Low Water Activity and High Fat Content

2013 ◽  
Vol 76 (2) ◽  
pp. 333-337 ◽  
Author(s):  
BRYAN AVILES ◽  
COURTNEY KLOTZ ◽  
TWYLA SMITH ◽  
ROBERT WILLIAMS ◽  
MONICA PONDER
Keyword(s):  
Water Activity ◽  
Salmonella Enterica ◽  
Peanut Butter ◽  
Gastric Fluid ◽  
Fat Content ◽  
Simulated Gastric Fluid ◽  
Food Matrix ◽  
High Fat ◽  
Low Fat ◽  
Infectious Dose

The low water activity (aw 0.3) of peanut butter prohibits the growth of Salmonella in a product; however, illnesses are reported from peanut butter contaminated with very small doses, suggesting the food matrix itself influences the infectious dose of Salmonella, potentially by improving Salmonella's survival in the gastrointestinal tract. The purpose of our study was to quantify the survival of a peanut butter outbreak–associated strain of Salmonella enterica serotype Tennessee when inoculated into peanut butters with different fat contents and aw (high fat, high aw; high fat, low aw; low fat, high aw; low fat, low aw) and then challenged with a simulated gastrointestinal system. Exposures to increased fat content and decreased aw both were associated with a protective effect on the survival of Salmonella Tennessee in the simulated gastric fluid compared with control cells. After a simulated intestinal phase, the populations of Salmonella Tennessee in the control and low-fat formulations were not significantly different; however, a 2-log CFU/g increase occurred in high-fat formulations. This study demonstrates that cross-protection from low-aw stress and the presence of high fat results in improved survival in the low pH of the stomach. The potential for interaction of food matrix and stress adaptations could influence the virulence of Salmonella and should be considered for risk analysis.

Risks of Salmonellosis and Staphylococcal Food Poisoning From Pakistani Milk-based Confectioneries

1992 ◽  
Vol 55 (8) ◽  
pp. 588-594 ◽  
Author(s):  
PAUL TEUFEL ◽  
FRANK L. BRYAN ◽  
FAHMIDA QADAR ◽  
SHAHID RIAZ ◽  
SABIHA ROOHI ◽  
...  
Keyword(s):  
Water Activity ◽  
Food Poisoning ◽  
High Water ◽  
Foodborne Illness ◽  
Milk Product ◽  
Control Points ◽  
Warm Environment ◽  
Critical Control Points ◽  
Retail Outlets ◽  
Concentrated Milk

Hazards of milk-based products were conducted in three confectionery manufacturing shops in a city in Pakistan. The incoming khoa (a heat-concentrated milk product having a water activity of approximately 0.97) was initially contaminated with staphylococci and contained enterotoxin. The confectionery was subsequently cooked to temperatures that would be lethal to staphylococci, but staphylococci were often found in high numbers in the finished products. Recontamination occurred during handling. Khoa-filled confectionery and confectionery made from renin-processed cheese were contaminated by salmonellae. The contaminants reached the products either during cooling or handling after cooking. Multiplication occurred in the warm environment of the shop and may continue in products having high water activity during transport and within retail outlets. Critical control points are source of ingredients (particularly khoa), formulation, cooking (except for preformed enterotoxins), cooling, and cold storage. Milk-based products of the types evaluated pose a high risk of causing foodborne illness.

Modification of a Predictive Model To Include the Influence of Fat Content on Salmonella Inactivation in Low-Water-Activity Foods

2020 ◽  
Vol 83 (5) ◽  
pp. 801-815
Author(s):  
LISA M. TRIMBLE ◽  
JOSEPH F. FRANK ◽  
DONALD W. SCHAFFNER
Keyword(s):  
Water Activity ◽  
Survival Data ◽  
Peanut Butter ◽  
Weibull Model ◽  
Fat Content ◽  
Mitigation Strategies ◽  
Model Parameters ◽  
Least Squares Regression ◽  
Salmonella Spp ◽  
Model Predictions

ABSTRACT Low-water-activity (aw) foods (including those containing fat) are often implicated in outbreaks of Salmonella spp. The influence of fat content on survival in foods such as peanut butter remains unclear. Certain Salmonella serovars can survive for long periods in harsh temperatures and low moisture conditions. The objective of this study was to determine the influence of fat content on the survival of Salmonella in low-aw foods and expand an existing secondary inactivation model previously validated for lower-fat foods. Whey protein powder supplemented with peanut oil was equilibrated to five target aw values (aw < 0.60), inoculated with a dried four-strain cocktail of Salmonella, vacuum sealed, and stored at 22, 37, 50, 60, 70, and 80°C for 48 h, 28 days, or 168 days. Survival data were fitted to Weibull, Biphasic-linear, Double Weibull, and Geeraerd-tail models. The Weibull model was chosen for secondary modeling due to its ability to satisfactorily describe the data over most of the conditions under study. The influence of temperature, fat content, and aw on the Weibull model parameters was evaluated using nonlinear least squares regression, and a revised secondary model was developed based on parameter significance. Peanut butter, chia seed powder, toasted oat cereal, and animal crackers within the aw range of the model were used to validate the modified model within its temperature range. Fat content influenced survival in samples held at temperatures ≥50°C, whereas aw influenced survival at 37 and 70°C. The model predictions demonstrated improved % bias and % discrepancy compared with the previous model. Weibull model predictions were accurate and fail-safe in 38 and 58%, respectively, of the food and environmental conditions under study. Predictions were less reliable for peanut butter held at 80°C. This study provides data and a model that can aid in the development of risk mitigation strategies for low-aw foods containing fat. HIGHLIGHTS

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