F. Castaigne

Effect of pre-harvest chitosan sprays on post-harvest infection by Botrytis cinerea and quality of strawberry fruit

The effect of pre-harvest sprays of chitosan on post-harvest decay and quality of strawberries stored at 3 and 13°C was investigated. Strawberry plants were sprayed with 2, 4 an d6gl 1 , chitosan solutions as the fruit were turning red. A second spray was performed after 10 days. Fruit were picked 5 and 10 days after each spray. Harvested fruit from chitosan sprayed plants were challenged with Botrytis cinerea. Chitosan sprays significantly reduced post-harvest fungal rot and maintained the keeping quality of the fruit compared with control. The incidence of decay decreased with increased chitosan concentration and increased with storage period and temperature. The second spray of chitosan extended the protective effect against decay of fruit from subsequent picks. Fruit from chitosan sprayed plants were firmer and ripened at a slower rate as indicated by anthocyanin content and titratable acidity than berries from non-treated plants. Chitosan sprays were not phytotoxic at all the concentrations tested. Chitosan sprays at 6 gl 1 concentration performed twice, 10 days apart, protected the fruit from decay and kept the fruit quality at an acceptable level throughout the storage period of 4 weeks in fruit stored at 3°C. The protective effect of chitosan sprays was more pronounced for fruit from pick 1 than pick 2. Kinetic data on decay and ripening characteristics provided quantitative evidence that chitosan compensates for higher storage temperature and protects against deterioration of lower quality fruit from the second harvest.

EVect of Chitosan on Growth and Toxin Production by Alternaria alternata f. sp. lycopersici

The antifungal activity of chitosan, a biopolymer of beta-1-4 glucosamine, against Alternaria alternata f. sp. lycopersici , causal agent of black mold of tomato, was investigated. Chitosan was incorporated into potato-dextrose broth at concentrations of 100-6400 mug ml - 1, and the growth and toxin production by the fungus were assessed after 15 days of incubation. At the higher concentrations, chitosan significantly aVected both fungal growth and toxin production. However, at lower concentrations toxin production was aVected more than growth. The fungus sporulated excessively in the presence of chitosan, but the spores were less viable. Chitosan also induced aggregation, abnormal shape, excessive branching and hyphal contortion of fungal cells, and leakage of proteins. The virulence of the toxin in culture filtrates of the fungus grown on diVerent concentrations of chitosan was assessed by administering toxin on tomato disks. The phospholipid content, electrolyte leakage and activities of xylanase and p...

Thermal and Physical Properties of Bakery Products

Referee: Dr. M R. Okos, Department of Agricultural Engineering, Purdue University, West Lafayette, IN 47907 This article reviews the measurement techniques, prediction models, and data on thermo-physical properties of bakery products: specific heat, thermal conductivity, thermal diffusivity, and density. Over the last decade, investigation has focused more on thermo-physical properties of nonbread bakery products. Both commonly used and new measurement techniques for thermo-physical properties reported in the publication are presented with directions for their proper use. Data and prediction models are tabulated for the range of moisture content and temperature of the bakery products.

Modified atmosphere preservation of freshly prepared diced yellow onion

Abstract The influence of controlled atmosphere storage conditions on the microbiological and sensory quality and the physiology of diced, ‘ready-to-use’ yellow onion was investigated. In the first experiment, diced onion was stored for 14 days at 4 °C and high relative humidity under a continuous stream of nitrogen containing (%O 2 /%CO 2 ): 20/0, 2/0, 2/5, 2/10 and 2/15. The tissue was sampled for microbiological and sensory analysis on days 0, 4, 9 and 14. In the second experiment, the diced onion was stored for 12 days at 4 °C under (%O 2 /%CO 2 ): 20/0, 2/0 and 2/10 treatments. Samples were collected on days 0, 4, 8 and 12 for physiological analysis. The following parameters were studied: mesophile and psychrotroph counts, pyruvate content (an index of flavor intensity), color, sensory quality, rate of respiration and sugar (fructose glucose, sucrose and total sugars) content. CO 2 enrichment of the atmosphere delayed diced onion deterioration. Microbial development was delayed, particularly that of the psychrotroph flora. Sensory quality was optimal under the 2% O 2 /10% CO 2 atmosphere. However, pyruvate and color determination showed no noticeable difference between treatments, although the period of storage significantly influenced these parameters. High CO 2 and low O 2 delayed the rise in respiration and the reduction in sucrose content, as compared with the control in air. Levels of reducing and total sugars remained constant throughout storage under all treatments. Browning after cooking developed with increasing length of storage, but was delayed by storage under 10% CO 2 . Involvement of sugars in this disorder is discussed. This work provides a basis for the development of modified atmosphere packs which will extend the preservation of the product for 2 weeks.

Cake baking in tunnel type multi-zone industrial ovens Part II. Evaluation of quality parameters

Abstract In addition to characterization of baking conditions during industrial cake baking, some important quality parameters, such as texture, color, density and viscosity of the cake batter were evaluated during baking in two different multi-zone industrial scale ovens: gas fired band oven and electric powered mold oven. The flow behavior of all batters was pseudo-plastic with a yield stress. The average moisture removal rates (3.59×10−4–1.40×10−3 kg H2O/kg solid s) of cakes fell between those of cookies and breads. During baking, pH increased and then decreased at the late stage of baking. Batter positions (side or center) on the band were not critical for quality parameters with the exception of moisture content. Most color changes occurred 1/4–3/4 way through the baking. After 21 days of storage, the hardness of all cakes increased 1.8–3 times the original value.

Storage of broccoli florets in ethanol vapor enriched atmospheres

Abstract Broccoli florets are highly perishable because the buds turn yellow rapidly. Exposure to an atmosphere enriched in ethanol vapor increased their storage life. The florets exposed to ethanol levels of 500, 1000 and 2500 ppm (± 10–15%) retained higher levels of chlorophyll than the control (0 ppm) stored for six days at 13 °C under water-saturated air. A level of 2500 ppm of ethanol in the atmosphere completely inhibited mold growth. A continuous treatment at 13 °C for six days with 2500 ppm did not have any effect on the floret respiration rate. In addition the weight loss of florets exposed to ethanol was significantly lower than that of control. However, this treatment induced undesirable off-odors in stored broccoli, presumably due to a high accumulation of ethanol and acetaldehyde in the tissue. On the other hand, shorter exposure to ethanol (12–24 h) with 2500 ppm of ethanol at 13 °C followed by air storage at 13 °C slowed down the loss of chlorophyll, compared to the control, and prevented the induction of off-odors in broccoli florets. Moreover, internal levels of ethanol and acetaldehyde of pre-treated buds decreased during six days of storage compared to the continuous treatment. It appears that a pre-treatment with ethanol vapor as an adjunct to moderate-temperature storage can be useful in the storage of broccoli.

Cake baking in tunnel type multi-zone industrial ovens Part I. Characterization of baking conditions

Abstract Baking conditions were observed for two different multi-zone industrial scale ovens: a gas fired band oven and an electric powered mold oven. In each zone of both ovens, parameters measured were: internal temperature profile, air velocity absolute humidity and oven wall temperature. Air temperatures were higher close to the oven wall than at the center of ovens tested. Absolute air humidity in the gas fired band oven (0.0545–0.246 kg H2O/kg dry air) was higher than in the electric fired mold oven (0.0207–0.0505 kg H2O/kg dry air). The relative air velocities in the ovens were 0–0.437 m/s, which resulted in convective heat transfer coefficients of 5.7–7.4 W/m2K and mass transfer coefficients of 3.94×10−8-5.12×10−8 kg/m2 s Pa. The average rate of total energy transferred to each product was 71992–85339 W. A proportion of 26–38.4% was the sensible heat absorbed with 61.6%–74% of the heat absorbed as the latent heat of vaporization of moisture. Radiative heat was responsible for 66.2–81.5% of the heat delivered to the top surface of products for cake baking in direct fired industrial ovens.

Production of alginate beads by a rotative atomizer

The use of a rotative flat disc atomizer for the production of biocatalysts immobilized in alginate gel was investigated. The influence of viscosity (0.28 to 1.53 Pa · s), disc diameter (5 to 20 cm), flow rate (0.5 to 2 L/min) and rotational speed (1.6 to 5 rev/s) on drop formation mechanisms, bead diameter and their distributions were investigated. Bead diameters ranging from 1 to 3 mm were been obtained. Flow rate and viscosity increases resulted in higher bead diameters but increasing disc diameter and rotational speed had a decreasing effect. A viscosity of 0.65 Pa · s would prove best for production of beads with good size distribution and mechanical strength. Predictive equations for the mean volumetric bead diameter were determined.

Effect of low temperature and controlled atmosphere storage on the membrane lipid composition of broccoli flower buds

Abstract The effect of low temperature and controlled atmosphere (CA) storage on the degradation of cell membranes was investigated during postharvest senescence of broccoli flower buds. Broccoli ( Brassica oleracea L., Italica group, cultivars ‘Stolto’, ‘Commander’ and ‘Green Valiant’) heads were stored for 6 or 9 weeks at 1 °C under atmospheres containing nitrogen and 0% CO 2 -20% O 2 (air) or 8.5% CO 2 -2.5% O 2 (CA). During storage in air the phospholipid content decreased and the free sterol : phospholipid ratio increased. These changes were delayed under CA. The slight increase in the degree of unsaturation of the phospholipid fatty acids observed during storage in air was also delayed under CA. Storage had little influence on sterol content. The results show good correlation between phospholipid degradation, increase in sterol : phospholipid ratio and postharvest senescence of broccoli flower buds. The development of treatments which would stabilise the cell membranes would be an important approach which would go to the root of the problem of postharvest conservation of broccoli.

Methodology for determining the appropriate selectivity of mass transfer devices for modified atmosphere packaging of fresh produce

Perforations or polymeric membranes are not capable of simultaneously providing optimum O 2 and CO 2 levels for many fruits and vegetables contained in modified atmosphere packaging. However, combining these two gas transfer devices, either in series or in parallel, can provide the required gas selectivities to create optimal modified atmosphere conditions. A methodology for determining the perforation and membrane surface areas for individual and combined systems is described. Gradient diagrams are used to calculate the optimum system selectivity, ΔpO 2 and ΔpCO 2 . These values can be used to select the appropriate gas exchange devices and to determine the appropriate perforation and membrane surface area.