Search results for "Water activity"

Inactivation of conidia of Penicillium chrysogenum, P. digitatum and P. italicum by ethanol solutions and vapours

2008

A fractional factorial design, 2(5-1) experiments, was used for assessing the influence of 5 factors: water activity, aw [0.7, 0.9], temperature, T ( degrees C) [10, 30], mode of application, A [liquid, vapour], ethanol concentration, E (% w/w) [5, 10] and time, t (d) [1, 4] on the inactivation of spores of Penicillium chrysogenum, P. digitatum and P. italicum. Survival was determined by germination at optimal conditions within 3d. The experimental response was log (N 0/Nt), where N 0 and Nt (spore ml(-1)) the concentrations of viable spores at t=0 and t respectively. By a decreasing order of sensitivity to ethanol, moulds were ranked as followed: P. digitatum, P. italicum and P. chrysogenu…

Modeling the effect of ethanol vapor on the germination time of Penicillium chrysogenum.

2005

The influence of ethanol vapor on germination of Penicillium chrysogenum was determined on yeast nitrogen base plus glucose agar medium at 25 degrees C. Ethanol vapors were generated by 0 to 6% (wt/wt) ethanol solutions at the bottom of hermetically closed petri dishes. The logistic equation was used to describe the data as the percentage of germination versus time and to estimate the germination time. The effect of ethanol concentration on germination time was described by a new reparameterized equation, resulting in an estimated limiting ethanol concentration of 4.3%. Up to 3% ethanol, all spores germinated, and the germination time increased with increasing ethanol concentration. At 3.5 …

Combined effect of natural antioxidants and antimicrobial compounds during refrigerated storage of nitrite-free frankfurter-type sausage.

2019

Abstract The effects of nisin (200 and 400 ppm), e-polylysine (0.1 and 0.2%) and chitosan (0.5 and 1%) in combination with a Mixed Extract (green tea, stinging nettle and olive leaves extracts) on the physicochemical, microbiological characteristics, fatty acid composition and sensory attributes of the nitrite-free frankfurter-type sausages were assessed during 45 days of storage. The results revealed no significant differences on moisture, fat, protein, ash, salt and water activity (aw) among treatments. 1% Chitosan + Mixed Extract sausages displayed the lowest thiobarbituric acid reactive substances (TBARS) and total volatile nitrogen (TVN) values compared to Control after 45 days of refr…

Desiccation by Exposure to Space Vacuum or Extremely Dry Deserts: Effect on Microorganisms

2003

General Limits of Growth at Low Water Activities Dormant Life Molecular Events Induced by Desiccation Survival at Extremely Low Water Activity Survival Under Extremely Dry Desert Conditions Keywords: anhydrobiosis; desiccation; extreme environments; freeze-drying; panspermia thesis; space: survival in space; space vacuum; water activity

The evaluation of drying kinetics and water activity of radish sprouts processed by different drying methods

2019

A novel alpha-amylase-lipase formulation as anti-staling agent in durum wheat bread

2016

The aim of this work has been to evaluate the anti-staling effect exerted by a novel α-amylase-lipase enzyme formulation on durum wheat bread, in comparison with four different commercial amylase preparations and with control without added enzymes. Bread-making trials were carried out at industrial level. Sliced bread, packed under modified atmosphere, was analyzed for texture profile, moisture content, and water activity during 90 days. Crumb sections were submitted to environmental scanning electron microscopy at the end of the storage period. The α-amylase-lipase enzyme preparation showed synergistic interactions in preventing staling. In particular, bread added of these two enzymes in m…

The role of water in the impact of high pressure on the myrosinase activity and glucosinolate content in seedlings from Brussels sprouts

2019

Abstract In this study, it was shown that the amount of available water was found to influence the high pressure processing (HPP) effect on both myrosinase activity and total glucosinolate concentration in Brussels sprouts seedlings. Brussels sprouts seedlings with different water content (wc = 4.8–89.4%) and water activity (aw = 0.17–0.97) were pressurized at selected pressures between 200 and 800 MPa (5 °C and 3 min), thereby affecting pressure-induced enzyme denaturation, molecular diffusion, and cell permeability differently. The myrosinase activity and intact glucosinolate content in the dry seedlings (wc  Industrial relevance High pressure processing (HPP) is increasingly applied in t…

Preparation of fungal conidia impacts their susceptibility to inactivation by ethanol vapours.

2009

Abstract A common protocol employed for the preparation of conidia employs flooding a fungal colony grown on semi-solid media under optimum conditions with an aqueous solution. In contrast, conidia produced in a natural environment are usually not hydrated when disseminated in air and can be produced under water stress. In order to simulate the latter conditions, cultures were grown at different water activities and conidia were dry-harvested on the lid by turning the dishes upside-down then gently tapping the bottom of the box. This study aimed at assessing the effect of the preparation of fungal conidia on their inactivation by ethanol vapours. Firstly ethanol vapours (either 0.30 or 0.45…

Significance of the physiological state of fungal spores.

2008

In predictive mycology, most of the studies have been concerned with the influence of some environmental factors on fungal growth and production of mycotoxins, at steady-state. However, fluctuating conditions, interactions between organisms, and the physiological state of the organisms may also exert a profound influence on fungal responses in food and in the environment. In the laboratory, fungal spores are widely used as a biological material. They are produced under optimal conditions then, partially re-hydrated for obtaining standardized spore suspensions. In real conditions, spores are produced under suboptimal conditions and can be submitted to various stresses prior to their germinat…

Moisture loss, gain and migration in foods and its impact on food quality

2010

Abstract: Moisture loss, gain and transfer, whether originating from exchanges with the atmosphere or with another component of the food, always cause deterioration in the overall quality of the food through softening, toughening, breakdown, and swelling or shrinkage caused by phase transitions or dissolution (Petersen et al., 1999). In most cases, water migrations lead to a deterioration of the overall quality (organoleptic or hygienic) of the food. With a view to better understanding physical deterioration of food and to provide a tool to better control food quality (and give a longer shelf life) this chapter reviews the water relationships in foods with a particular focus on glass-transi…