Silvana Martini

Altering Functional Properties of Fats Using Power Ultrasound

Ultrasound has been used for the last 50 y in different processing applications. Depending on the power and frequency of the sound waves, ultrasound techniques can be classified in different categories. Low-intensity ultrasound uses high frequencies in the range of 100 kHz to 10 MHz and is mostly used for therapeutic purpose (frequencies between 1 and 10 MHz) and to passively monitor the characteristics of materials (frequencies between 100 kHz and 10 MHz). High-intensity ultrasound (HIU), on the other hand, uses lower frequencies in the range of 20 to 100 kHz and it is commonly used for cleaning, disrupting, and restructuring materials. The objective of this study is to evaluate the effect of HIU on functional properties of anhydrous milk fat (AMF), palm kernel oil (PKO), and an all-purpose shortening (Sh). Results from this research shows that HIU induced primary and secondary nucleation in the lipid, generating smaller crystals and as a consequence harder materials. HIU affected hardness more efficiently when applied at higher crystallization temperatures (26 and 28 degrees C) as shown for AMF data, and when the sonication was applied after the first crystals were formed as observed for PKO and Sh systems. In addition to changes in hardness, AMF and Sh networks obtained after sonication were characterized by a steeper and sharper melting profile. This research shows that HIU can be used as an additional processing tool to tailor the functional properties of lipids with the potential to be used in the processing of trans-free shortenings.

Control of Listeria monocytogenes in Ready-to-Eat Meats Containing Sodium Levulinate, Sodium Lactate, or a Combination of Sodium Lactate and Sodium Diacetate

This study investigated the use of sodium levulinate to prevent outgrowth of Listeria monocytogenes in refrigerated ready-to-eat (RTE) meat products. Turkey breast roll and bologna were formulated to contain 1%, 2%, or 3% (w/w) sodium levulinate, 2% sodium lactate, a 2% combination of sodium lactate and sodium diacetate (1.875% sodium lactate and 0.125% sodium diacetate), or no antimicrobial (control). Samples of the RTE products were sliced, inoculated with 10(2) to 10(3) CFU/cm(2) of a 5-strain cocktail of L. monocytogenes, vacuum packaged, and stored at refrigeration temperature for 0 to 12 wk. Counts reached 10(8) CFU/cm(2) on control turkey roll product after 8 wk, and over 10(7) CFU/cm(2) on control bologna after 12 wk. Addition of 2% or more sodium levulinate to turkey roll and 1% or more sodium levulinate to bologna completely prevented growth of L. monocytogenes during 12 wk of refrigerated storage. A consumer taste panel with pathogen-free samples found no differences in the overall liking among the preparations of turkey roll or among preparations of bologna. These results show that sodium levulinate is at least as effective at inhibiting outgrowth of L. monocytogenes in RTE meat products as the current industry standards of lactate or lactate and diacetate, and levulinate addition does not alter the overall liking of the RTE meat products.

Using High Intensity Ultrasound as a Tool To Change the Functional Properties of Interesterified Soybean Oil

High intensity ultrasound (HIU) was used to change the crystallization behavior, generate small crystals, and improve the texture of a low saturated shortening (interesterified soybean oil). Samples were crystallized at different temperatures (26, 28, 30, and 32 °C) without and with the application of HIU. Different acoustic power levels (110, 72, 61, 54, and 44 W) were used. Results show that higher acoustic powers had a greater effect on crystal size reduction, induced crystallization, and generated harder, more elastic and viscous materials. These effects were more significant when HIU was applied in the presence of crystals and when the sample was crystallized at 32 °C.

Fortification of reduced-fat Cheddar cheese with n-3 fatty acids: effect on off-flavor generation.

The objective of this study was to fortify 50% reduced fat Cheddar cheese with n-3 fatty acids and evaluate whether this fortification generated specific off-flavors in the cheese. Docosahexaenoic (DHA) and eicosapentaenoic (EPA) fatty acids were added to the cheese to obtain 3 final fortification levels [18, 35, and 71 mg of DHA/EPA per serving size (28 g) of cheese] representing 10, 20, and 40% of the suggested daily intake level for DHA/EPA. The presence of oxidized, rancid, and fishy flavors as a function of fortification level and cheese aging (6 mo) was evaluated using a sensory descriptive panel. No differences were found in the oxidized and rancid flavors as a consequence of DHA/EPA fortification, with only slight intensities of these flavors. The presence of fishy off-flavor was dependent on the fortification level. Cheeses with low fortification levels (18 and 35 mg of DHA/EPA per serving size) did not develop significant fishy off-flavor compared with the control, whereas at the highest fortification level (71 mg of DHA/EPA per serving size) the fishy off-flavor was significantly stronger in young cheeses. The fishy flavor decreased as a function of age and became nonsignificant compared with the control at 3 mo of storage. Even though fishy flavors were detected in the fortified cheeses, the DHA/EPA content during storage remained constant and complied with the suggested values for food fortification. Results obtained from this research indicate that 50% reduced-fat Cheddar cheese aged for 3 mo can be used as a vehicle for delivery of n-3 fatty acids without generation of off-flavors.

Crystallization Behavior of Anhydrous Milk Fat-Sunflower Oil Wax Blends

This research evaluates the effect of sunflower oil wax (SFOw) addition on the crystallization behavior and functional properties of anhydrous milk fat (AMF). Induction times of nucleation, melting behavior, microstructure of crystals, and hardness were evaluated for samples of pure AMF and AMF with 0.1 and 0.25% SFOw. Results from this research show that the addition of waxes induced the onset of crystallization of AMF by inducing its nucleation, as evidenced by decreased induction times of nucleation and the formation of smaller crystals. Crystal growth after tempering was also promoted by waxes, and significantly harder lipid networks were obtained. Results presented in this paper suggest that SFOw can be used as an additive to alter the physiochemical properties of low trans-fatty acid lipids.

Fortification of Cheese with Vitamin D3 using Dairy Protein Emulsions as Delivery Systems

Vitamin D is an essential vitamin that is synthesized when the body is exposed to sunlight or after the consumption of fortified foods and supplements. The purpose of this research was to increase the retention of vitamin D(3) in Cheddar cheese by incorporating it as part of an oil-in-water emulsion using a milk protein emulsifier to obtain a fortification level of 280 IU/serving. Four oil-in-water vitamin D emulsions were made using sodium caseinate, calcium caseinate, nonfat dry milk (NDM), or whey protein. These emulsions were used to fortify milk, and the retention of vitamin D(3) in cheese curd in a model cheesemaking system was calculated. A nonemulsified vitamin D(3) oil was used as a control to fortify milk. Significantly more vitamin D(3) was retained in the curd when using the emulsified vitamin D(3) than the nonemulsified vitamin D(3) oil (control). No significant differences were observed in the retention of vitamin D(3) when emulsions were formulated with different emulsifiers. Mean vitamin D(3) retention in the model system cheese curd was 96% when the emulsions were added to either whole or skim milk compared with using the nonemulsified oil, which gave mean retentions of only 71% and 64% when added to whole and skim milk, respectively. A similar improvement in retention was achieved when cheese was made from whole and reduced-fat milk using standard manufacturing procedures on a small scale. When sufficient vitamin D(3) was added to produce cheese containing a target level of approximately 280 IU per 28-g serving, retention was greater when the vitamin D(3) was emulsified with NDM than when using nonemulsified vitamin D(3) oil. Only 58±3% of the nonemulsified vitamin D(3) oil was retained in full-fat Cheddar cheese, whereas 78±8% and 74±1% were retained when using the vitamin D(3) emulsion in full-fat and reduced-fat Cheddar cheese, respectively.

Increasing omega fatty acid content in cow's milk through diet manipulation: Effect on milk flavor

Milk with an increased content of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and conjugated linoleic acid (CLA) was obtained by incorporating fish oil into the feed of cows. The 4 feed treatments used were a control diet of 57% forage and 43% concentrate mix with EnerGII fat supplement at 1.65% of dietary DM, or EnerGII in the basal diet was partially replaced with 1) 0.21% partially ruminally inert calcium salts of 71% fish oil given at 0.41% of DM; 2) 0.41% inert calcium salts of 71% fish oil given at 0.83% of DM; or 3) 0.83% inert calcium salts of 43% fish oil given at 0.83% of DM. The cows were milked after 5 and 8 wk and the EPA, DHA, and CLA contents in the pasteurized whole milk were determined. The presence of off-flavors in the milk was investigated after 3 and 10 d of storage. Twelve judges were trained to evaluate the presence of grassy, fishy, oily, oxidized, and rancid off-flavors. Although levels of EPA, DHA, vaccenic acid, and CLA increased for all 4 treatments, a trained sensory panel detected no difference in milk flavor between treatments and the control, with little or no intensity of off-flavors. Results suggest that feeding fish oil and EnerGII at varying levels enhanced CLA, EPA, DHA, and total n-3 fatty acids in milk over the length of the experiment without negatively affecting milk flavor. This creates the potential for a more marketable and healthful product.

Influence of ι-carrageenan, pectin, and gelatin on the physicochemical properties and stability of milk protein-stabilized emulsions.

UNLABELLED This study evaluated the stability of bilayer emulsions as a function of secondary layer composition and pH. Primary emulsions were formulated with 5% soybean oil, 1% protein from nonfat dry milk (NDM) powder as emulsifier and ι-carrageenan (ι-carr), low-methoxyl pectin (LMp), high-methoxyl pectin (HMp), or gelatin as secondary layers. ζ-Potential values increased for each emulsion as the pH decreased, with ι-carr emulsions being consistently more negatively charged than primary emulsions and significantly more stable. ζ-Potential values were not always correlated to emulsion stability. Gelatin secondary emulsions at pH 3 and HMp secondary emulsions at pH 7 were unstable due to the presence of depletion flocculation. In addition, LMp secondary emulsions stability at pH 7 might be due to calcium bridging, which increased the emulsions viscosity. Overall, the stability of NDM emulsions was improved when ι-carr and LMp were used as secondary layers at pH 7 and 5, and when ι-carr and HMp were used as secondary layers at pH 3. Increased stability of these systems can be attributed to a second homogenization step used to formulate the secondary emulsions and to the presence of Ca(+2) in the NDM. Results from this research show that the stability of bilayer emulsions is driven by the presence of depletion flocculation, droplet charge, droplet size and distribution and viscosity. PRACTICAL APPLICATION The use of everyday ingredients (nonfat dry milk powder, gelatin, pectin, and carrageenan), which are understood and accepted by the average consumer, creates label-friendly products that are the wave of the future. Stable emulsions can be formed using these ingredients at various pH. Understanding the stability and how the pH impacts the physicochemical characteristics and stability of these emulsions will enable manufactures to use ordinary ingredients to create healthier products (for example, low-fat dressings, sauces, dips, and beverages).

Application of high-intensity ultrasound to palm oil in a continuous system.

High-intensity ultrasound (HIU) was used in a continuous system to change the crystallization behavior of palm oil. Different power levels (75, 110, and 180 W) and pulse durations (continuous application and 5, 10, and 15 s pulses) were used to optimize sonication conditions. Results showed that HIU applied at low power level (75 W) was the most efficient condition in inducing palm oil crystallization at 35 °C, generating a crystalline network with higher solid fat content (SFC), higher elasticity, and sharper melting profile after 60 min of crystallization. Changes in elasticity observed as a consequence of sonication were maintained after tempering the samples at 25 °C for 24 h, but were lost after tempering at 5 °C. No significant differences (α = 0.05) were observed in SFC values of the sonicated and nonsonicated samples after tempering, whereas the sharper melting behavior observed in the sonicated sample was maintained after tempering.

Comparison of milk oxidation by exposure to LED and fluorescent light

Light-induced oxidation of milk has been well studied. Exposure of milk to UV light facilitates the oxidation of fats to aldehydes, and the degradation of sulfur-containing amino acids, both of which contribute to off-flavors. In addition, vitamin A and riboflavin are easily degraded by UV light. These reactions occur rapidly and are exacerbated by bright fluorescent lights in retail dairy cases. The invention of white light-emitting diodes (LED) may provide a solution to this oxidation problem. In this study, fresh milk containing 1% fat and fortified with vitamin A and riboflavin was exposed to LED at 4,000 lx, or fluorescent light at 2,200 lx for 24 h. Milk samples exposed to LED or fluorescent light, as well as milk protected from light, were analyzed by a consumer acceptance panel, and a trained flavor panel. In addition, vitamin A, riboflavin, and the production of volatile compounds were quantified. Exposure to light resulted in a reduction of cooked/sweet, milkfat, and sweet flavors and increased the intensity of butterscotch, cardboard, and astringency. In general, exposure to fluorescent light resulted in greater changes in the milk than exposure to LED even though the LED was at higher intensity. Consumers were able detect off-flavors in milk exposed to fluorescent light after 12 h and LED after 24 h of exposure. The riboflavin and vitamin A content was reduced by exposure to fluorescent light, whereas there was no significant reduction caused by LED compared with the non-light-exposed control. Production of hexanal, heptanal, 2-heptanal, octanal, 2-octanal nonanal, dimethyl sulfide, and caproic acid vinyl ester from the light-induced degradation of fats was significantly higher with fluorescent than LED. Production of these compounds was significantly higher with both light treatments than in the control milk. This study indicates that LED is less destructive to milk than fluorescent light.