Sheryl A. Barringer

Flow property measurement of food powders and sensitivity of Jenike’s hopper design methodology to the measured values

Abstract The flow properties and powder physical properties were measured for 13 food powders. The flow properties were measured using shear cell techniques, and the powder physical properties measured were particle size, moisture, bulk and particle densities. The flowability of the food powders, as characterised by flow index, varied from easy flow to very cohesive. Particle size and moisture content do affect flowability, however there was no strong relationship for trying to relate the flowability of the food powders based solely on these physical properties. There was no relationship between measured powder physical properties and their wall friction characteristics. As a result, surface forces between the powder particles, and between particles and the wall surface play an important role in determining the flow nature of the powders, and this is an area requiring research. Jenike’s mathematical analysis to determine the minimum hopper angle and opening size for mass flow is the engineering standard practice for designing a hopper. Applying this analysis, using values of the measured food powder flow properties, shows that this can occasionally produce some unexpected values for the hopper opening size.

The role of seed coats in seed viability

The seed coat is the seed’s primary defense against adverse environmental conditions. A hard seed coat protects the seed not only from mechanical stress but also from microorganism invasion and from temperature and humidity fluctuations during storage. Phenolic compounds in the seed coat contribute to seed hardness and inhibition of microorganism growth. During germination, the seed coat protects the seed from hydration stress and electrolyte leakage.ResumenLa cubierta de la semilla es la defensa primaria contra el medio ambiente adversa. Una cubierta dura proteja la semilla no solo de tensión mecanica sino también de ana invasion de microorganismos y de cambios en temperatura y humedad durante almacenaje. Los phenolics en la cubierta de la semilla contribuyan a la dureza de la semilla y la inhibitión de crecimiento de microorganismos. Durante la germinatión, la cubierta proteja la semilla de la tension de hidratación y del escape de electrolytes.

Use of Dielectric Properties to Detect Whey Protein Denaturation

Denaturation of whey proteins can be detected by the dielectric properties. The dielectric properties of 20% whey protein with 0, 5 or 15% sugar, 2% salt, at pH 4 and isolated whey proteins were measured from room temperature to 100°C at 300–2450 MHz. The temperature at which a decrease in the dielectric loss factor, or increase in the dielectric constant, occurred was compared to the temperature of denaturation as determined by DSC and found to match. The change in the dielectric properties is likely caused by binding of water and/or ions that occurs during protein denaturation. For most of the samples, the dielectric loss factor showed the protein denaturation, but when ions were present due to salt or low pH, the dielectric constant showed the denaturation.

Effect of Roasting Conditions on Color and Volatile Profile Including HMF Level in Sweet Almonds (Prunus dulcis)

UNLABELLED Microwave, oven, and oil roasting of almonds were used to promote almond flavor and color formation. Raw pasteurized almonds were roasted in a microwave for 1 to 3 min, in an oven at 177 °C for 5, 10, 15, and 20 min; and at 135 and 163 °C for 20 min, and in oil at 135, 163, and 177 °C for 5 min and 177 °C for 10 min. Volatile compounds were quantified in the headspace of ground almonds, both raw and roasted, by selected ion flow tube mass spectrometry. Strong correlations were found between L value, chroma, and 5-(hydroxy methyl)-2- furfural; and were independent of roasting method. Raw almonds had lower concentrations of most volatiles than roasted almonds. Conditions that produced color equivalent to commercial samples were 2 min in the microwave, 5 min at 177 °C in the oven, and 5 min at 135 °C in oil. Microwave heating produced higher levels of most volatiles than oven and oil roasting at commercial color. Sensory evaluation indicated that microwave-roasted almonds had the strongest aroma and were the most preferred. Oil-roasted almonds showed significantly lower levels of volatiles than other methods, likely due to loss of these volatiles into the oil. Alcohols such as benzyl alcohols and strecker aldehydes including benzaldehyde and methional were at higher concentrations than other volatiles in roasted almonds. The oxidation of lipids to form alkanals such as nonanal and degradation of sugars to form furan type compounds was also observed. The Maillard reaction contributed to the formation of more of the total volatiles in almonds than the lipid oxidation reaction. PRACTICAL APPLICATION The level of 5-(hydroxy methyl)-2- furfural (HMF), color, volatile profile, and sensory perception can be used to develop the best roasting method, time, and temperature for almonds. The rate of color development and the production of volatiles differ under different roasting conditions. Based on the color, volatile, and sensory assessments of the 3 almonds, the use of microwave technology as a process for roasting almonds reduces processing time and leads to an almond product with better flavor than oven or oil roasting.

Effect of Temperature on Lipid-Related Volatile Production in Tomato Puree

Lipid-related volatiles were measured in real time after the blending of grape tomatoes, using selected ion flow tube mass spectrometry (SIFT-MS). Measurements were made at 4, 23, or 37 degrees C. The volatiles in the headspace of the tomatoes, other than hexanal, increased with increasing temperature. The concentration of hexanal in the headspace increased from 4 to 23 degrees C, but decreased at 37 degrees C. The activity of hexanal-specific hydroperoxide lyase decreases at 37 degrees C. Moreover, precursors of hexanal may go through alternative pathways to form trans-2-heptenal and trans-2-octenal. The increase in concentration in the headspace for most volatiles can be explained by the increase in volatility, except for trans-2-heptenal, trans-2-octenal, and trans-2-pentenal. These three volatiles appear to be generated at a much higher rate at 37 degrees C due to the dominance of alternate pathways at this temperature. Temperature did not affect the time to peak level for most volatiles, except the time for hexanal was shorter with increasing temperature. A temperature-dependent lipoxygenase pathway was postulated.

Rapid propagation of tuna (Opuntia ficus-indica) and plant establishment in soil

Explants from young joints of mature plants of tuna (Opuntia ficus-indica Mill.) were cultured on Murashige and Skoog (MS) medium containing 8.8 μM benzyladenine (BA) and 0.5 μM naphthaleneacetic acid (NAA). Shoots produced were utilized as secondary explants. Each shoot was cut longitudinally from apex to base into two explants, and some of these explants were cut transversely into proximal and distal explants. The size and number of shoots produced was affected by size and position of the explant within its source. The shoots were rooted in vitro or ex vitro and plants were successfully established in soil from both rooting methods.

In vitro shoot proliferation and propagation of guava (Psidium guajava L.) from germinated seedlings

Guava seeds were germinated on Murashige and Skoog (MS) medium with or without 8.8 μM benzyladenine (BA). BA increased the rate of germination and the number of lateral shoots (3.4 vs 1.2 per seedling). Stem nodes from these lateral shoots were cultured on proliferation media with 4.4 μM BA, and multiple shoots (3.5) were formed within 4 weeks of culture. Increasing the concentration of BA or the addition of naphthaleneacetic acid (NAA) did not affect shoot formation. Shoots produced from explants and lateral shoots from germinated seedlings were rooted in media containing activated charcoal (AC) or 9.8 μM indolebutyric acid (IBA). Shoots rooted with IBA had a higher rooting percentage (100% vs 75%) and a greater number of roots (5.5 vs 3.2) but the shoots were shorter (2.6 vs 3.4 cm) than when rooted in AC, and they required an additional 4 weeks of culture in media with AC to achieve shoot elongation. About 80% of the shoots with roots survived in the glasshouse and produced normal phenotypic plants.

Modelling the effect of pH on the colour degradation of blanched broccoli

In ready-to-eat salads, a low pH is often applied in the salad dressing. The effect of pH on the colour change of blanched-frozen-and-thawed broccoli was studied. Different acids were used to achieve the pH values in buffer solutions. A model on chlorophyll degradation in fruits and vegetables was developed based on a simplification of existing knowledge. From integral non-linear regression analysis, it was concluded that the pH gradient at the boundary between product and buffer solution had a marked effect at low pH values. Furthermore, based on the analyses and the obtained residuals, another colour degrading process was revealed that gradually increases in relative importance at higher pH values. The effect of the five acids applied could be attributed to a single proportionality factor, probably related to the hydrophilic nature of the acid applied. The statistical analysis showed a percentage variance accounted for (R2adj) of more than 99.6ÐThe apparent rate of colour degradation was found to be linearly related to the concentration of hydrogen ions. ? 2001 Elsevier Science Ltd. All rights reserved.

Effect of Enzymes on Strawberry Volatiles during Storage, at Different Ripeness Level, in Different Cultivars, and during Eating

UNLABELLED Strawberry samples with enzyme activity and without enzyme activity (stannous chloride added) were measured for real-time formation of lipoxygenase (LOX) derived aroma compounds after 5 min pureeing using selected ion flow tube-mass spectrometry (SIFT-MS). The concentration of (Z)-3-hexenal and (E)-2-hexenal increased immediately after blending and gradually decreased over time, while hexanal concentration increased for at least 5 min in ground strawberries. The formation of hexanal was slower than the formation of (Z)-3-hexenal and (E)-2-hexenal in the headspace of pureed strawberries. The concentration of LOX aldehydes and esters significantly increased during refrigerated storage. Damaging strawberries increased the concentration of LOX aldehydes but did not significantly affect the concentration of esters. The concentrations of many of the esters were strongly correlated to their corresponded acids and/or aldehydes. The concentration of LOX-generated aldehydes decreased during ripening, while fruity esters increased. Different varieties had different aroma profiles and esters were the greatest percentage of the volatiles. The aroma release of some of the LOX-derived aldehydes in the mouthspace in whole strawberries compared to chopped strawberries showed that these volatiles are formed in the mouth during chewing. The persistence of LOX-derived compounds was higher than esters after swallowing. The mouthspace after and before swallowing persistence ratio of esters decreased as the chain length of the acid part of the ester compounds increased in whole strawberries. PRACTICAL APPLICATION The storage studies showed that the concentrations of fruity and fresh volatiles increased during ripening and storage while damaging only increases the fresh volatiles. The nose, mouth, and headspace information can be used in the flavor industry to improve the formula of natural strawberry flavor by considering human perception during eating.

Effect of Milk on the Deodorization of Malodorous Breath after Garlic Ingestion

The effect of milk and milk components on the deodorization of diallyl disulfide (DADS), allyl methyl disulfide (AMDS), allyl mercaptan (AM), allyl methyl sulfide (AMS), and methyl mercaptan (MM) in the headspace of garlic as well as in the mouth- and nose-space after garlic ingestion was investigated using selected ion flow tube-mass spectrometry (SIFT-MS). Fat-free and whole milk significantly reduced the head-, mouth-, and nose-space concentrations of all volatiles. Water was the major component in milk responsible for the deodorization of volatiles. Due to its higher fat content, whole milk was more effective than fat-free milk in the deodorization of the more hydrophobic volatiles diallyl disulfide and allyl methyl disulfide. Milk was more effective than water and 10% sodium caseinate in the deodorization of allyl methyl sulfide, a persistent garlic odor, in the mouth after garlic ingestion. Addition of milk to garlic before ingestion had a higher deodorizing effect on the volatiles in the mouth than drinking milk after consuming garlic. Practical Application: Ingesting beverages or foods with high water and/or fat content such as milk may help reduce the malodorous odor in breath after garlic ingestion and mask the garlic flavor during eating. To enhance the deodorizing effect, deodorant foods should be mixed with garlic before ingestion.