Rosana G. Moreira

Vacuum frying of potato chips

Vacuum frying was tested as an alternative technique to develop low oil content potato chips. The effect of oil temperature (118, 132, 144 C) and vacuum pressure (16.661, 9.888, and 3.115 kPa) on the drying rate and oil absorption of potato chips and on the product quality attributes such as shrinkage, color, and texture was investigated. Furthermore, the characteristics of the vacuumfried potato chips (3.115 kPa and 144 C) were compared to potato chips fried under atmospheric conditions (165 C). During vacuum frying, oil temperature and vacuum pressure had a significant effect on the drying rate and oil absorption rate of potato chips. Potato chips fried at lower vacuum pressure and higher temperature had less volume shrinkage. Color was not significantly affected by the oil temperature and vacuum pressure. Hardness values increased with increasing oil temperature and decreasing vacuum levels. Potato chips fried under vacuum (3.115 kPa and 144 C) had more volume shrinkage, were slightly softer, and lighter in color than the potato chips fried under atmospheric conditions (165 C). It was concluded that vacuum frying is a process that could be a feasible alternative to produce potato chips with lower oil content and desirable color and texture. 2002 Elsevier Science Ltd. All rights reserved.

Factors affecting oil uptake in tortilla chips in deep-fat frying

Abstract An understanding of the complex processes that occur during frying is necessary to control the quality of tortilla chips. Quantitative information is needed to describe the rate of oil absorption into the chips during the process. In this study, tortilla chips were processed under different conditions: (1) baking time, (2) frying oil temperature, (3) particle size distribution, and (4) oil quality. The effects of these parameters on the final oil content of tortilla chips were analyzed. Oil content of tortilla chips was significantly ( P The final oil content to water removed ratio was independent of frying oil temperature. It was also found that the total final oil content was not affected by oil quality, but the oil distribution was different. Tortilla chips fried in used oil had more oil accumulated at the surface than tortilla chips fried in fresh oil. The higher viscosity and/or lower surface tension of the used oil could cause the oil to adhere to the products surfaces. Results showed that only 20% of the total final oil content was absorbed by the tortilla chips during frying, and 64% during cooling, leaving only 36% at the chips surface.

Poly (DL‐lactide‐co‐glycolide) (PLGA) Nanoparticles with Entrapped trans‐Cinnamaldehyde and Eugenol for Antimicrobial Delivery Applications

UNLABELLED Eugenol and trans-cinnamaldehyde are natural compounds known to be highly effective antimicrobials; however, both are hydrophobic molecules, a limitation to their use within the food industry. The goal of this study was to synthesize spherical poly (DL-lactide-co-glycolide) (PLGA) nanoparticles with entrapped eugenol and trans-cinnamaldehyde for future antimicrobial delivery applications. The emulsion evaporation method was used to form the nanoparticles in the presence of poly (vinyl alcohol) (PVA) as a surfactant. The inclusion of antimicrobial compounds into the PLGA nanoparticles was accomplished in the organic phase. Synthesis was followed by ultrafiltration (performed to eliminate the excess of PVA and antimicrobial compound) and freeze-drying. The nanoparticles were characterized by their shape, size, entrapment efficiency, and antimicrobial efficiency. The entrapment efficiency for eugenol and trans-cinnamaldehyde was approximately 98% and 92%, respectively. Controlled release experiments conducted in vitro at 37 °C and 100 rpm for 72 h showed an initial burst followed by a slower rate of release of the antimicrobial entrapped inside the PLGA matrix. All loaded nanoparticles formulations proved to be efficient in inhibiting growth of Salmonella spp. (Gram-negative bacterium) and Listeria spp. (Gram-positive bacterium) with concentrations ranging from 20 to 10 mg/mL. Results suggest that the application of these antimicrobial nanoparticles in food systems may be effective at inhibiting specific pathogens. PRACTICAL APPLICATION Nanoencapsulation of lipophilic antimicrobial compounds has great potential for improving the effectiveness and efficiency of delivery in food systems. This study consisted of synthesizing PLGA nanoparticles with entrapped eugenol and trans-cinnamaldehyde. By characterizing these new delivery systems, one can understand the controlled-release mechanism and antimicrobial efficiency that provides a foundation that will enable food manufacturers to design smart food systems for future delivery applications, including packaging and processing, capable of ensuring food safety to consumers.

A new approach to describe oil absorption in fried foods: a simulation study

The mechanism of oil absorption of tortilla chips during cooling was analyzed using capillary pressure theory. The experimental and theoretical results obtained with this mechanistic model agreed well. Computer simulations were made to determine the effect of different process conditions on the final product oil content. The results show higher oil content for tortilla chips with higher initial moisture content, smaller radius, lower cooling air temperature, and higher interfacial tension.

Impingement drying of foods using hot air and superheated steam

Impingement drying is an old technology that has only recently been applied to food products. Tortilla and potato chips, pizza crust, pretzels, crackers, and cooks, for example, have been successfully cooked and baked in air-impingement ovens in the food industry. Granular products (coffee beans, cocoa beans, rice, nuts) dry faster and more uniformly when using impingement dryers due to the pseudofluidized bed created by the high-velocity air from the nozzles. Tortilla chips and potato chips have been impingement dried using hot air and superheated steam. At higher air temperatures (above 130°C), tortilla chips dry faster when using superheated steam compared to hot air (at the same conditions). Impingement drying with superheated steam can produce potato chips with less color deterioration and less nutritional losses (Vitamin-C) than drying with hot air. Potato chips dry faster at high superheated steam temperature and high convective heat transfer coefficients.

Modeling the transport phenomena and structural changes during deep fat frying Part I: model development

A fundamental 2-D model was developed to predict the heat and mass transfer that occur during the frying and cooling process of tortilla chips. Semi-empirical correlations were included to account for structural changes, such as shrinkage and expansion due to puffing. All water present in the tortilla chip was considered bound and led to shrinkage when removed. The parameters that were studied included water saturation, Sw, oil saturation, So, temperature, T, and pressure, P. Liquid flow results from convective flow due to the gradient in total gas pressure and capillary flow due to the gradient of capillary force. Gas movement results from convective flow due to the total gas pressure gradient and Knudsen diffusion due to the concentration gradient. The only transport phenomenon during cooling is oil absorption, which is assumed to be a function of the capillary pressure. � 2002 Elsevier Science Ltd. All rights reserved.

SUPERHEATED STEAM IMPINGEMENT DRYING OF TORTILLA CHIPS

ABSTRACT Low-fat snack products are the driving forces for the drying of tortilla chips before frying. Super-heated steam impingement drying of foods has the advantage of improved energy efficiency and product quality. The temperature profile, drying curves, and the physical properties (shrinkage, crispiness, starch gelatinization and microstructure) of tortilla chips dried at different superheated steam temperatures and heat transfer coefficients were measured. Results indicated that the steam temperature had a greater effect on the drying curve than the heat transfer coefficient within the range of study. The microstructure of the samples after steam drying showed that higher steam temperature resulted in more pores and coarser appearance. The modulus of deformation and the shrinkage of tortilla chips correlated with moisture content. A higher steam temperature caused less shrinkage and a higher modulus of deformation. The pasting properties showed that samples dried under a higher steam temperature and...

Modeling the transport phenomena and structural changes during deep fat frying Part II: model solution & validation

Abstract A fundamental two-dimensional model to predict the heat and mass transfer that occur during the frying and cooling process of tortilla chips was solved using finite element technique. The assembly of elements method with each element being four-noded quadrilateral elements was used to obtain a two-dimensional distribution. The Gauss–Legendre method was used for the numerical integration of each of the integrals. The system of non-linear equations (including contributions from all elements) was solved using FORTRAN Power Station 4.0. A good agreement between experimental and predicted data was obtained. The parameters that were studied included water saturation, oil saturation, temperature during frying and cooling. Change in structure (shrinkage and expansion) was also verified and agreed well with the experimental data. Sensitivity analysis showed that the higher frying temperature the faster drying rate and a faster increase in the temperature and pressure of the product. More oil was absorbed at a lower frying temperature. The thicker the product the lesser the oil content. Oil absorption appeared to seize once the temperature of the product begins to increase and a crust begins to form. The cooling temperature had the most influence on oil absorption. The cooling temperature that was nearest to the temperature of the fried product led to the least amount of oil absorption.

Characterization of product quality attributes of tortilla chips during the frying process

Characterization of product quality attributes (PQA) of tortilla chips during frying will provide critical information that can be used to develop fundamental models to describe the structural changes of a fried product during frying. Tortilla chips were prepared from nixtamalized dry-masa flour and fried in fresh vegetable oil for 60 s. The results indicated that most diameter shrinkages of tortilla chips happened during the first 5 s of frying. The chips thickness increased as a result of crust formation and some bubbles developed at the surface due to gas expansion. The chips become more porous (pore size increased in number and size). The pore size distribution became more uniform (normal) as frying time increased. The chips became crunchier as moisture decreased during frying. The combination of all these quality attributes is responsible for producting the best final product as oil content is greatly affected by the mechanism of structure formation thus resulting in the desired product texture. Fundamental properties such as isotherms and glass transition temperatures were also evaluated. The Crapiste and Rotstein model provided the best correlation at the entire range of moisture content and temperatures. The glass transition termperatures were fitted using the Gordon and Taylor equation. The glass transition curve for the fried chips with total oil content is higher than the one for the chips with partial oil content. A model was developed using the extreme value distribution to predict the pore size distribution of tortilla chips during frying.

Application of high hydrostatic pressure to eliminate Listeria monocytogenes from fresh pork sausage.

Ground pork patties were inoculated separately with 10(9) CFU/g each of three strains of Listeria monocytogenes obtained from the National Animal Disease Center (NADC). Inoculated patties were packaged under vacuum and treated at 414 megapascals (60,000 lb/in2) for up to 60 min by high hydrostatic pressure (HHP). Survivors were determined by surface plating onto modified Oxford agar and trypticase soy agar with yeast extract, as well as by the most probable number method using Listeria enrichment broth. Average D values ranged from 1.89 to 4.17 min, depending on the strain, with the most virulent strain (reported by the NADC) having the highest D value. We tested the usefulness of applying a mild heat treatment at 50 degrees C, simultaneously with HHP, to lower these values. Average D values ranged from 0.37 to 0.63 min, depending on the strain. Thus, a 10-log10 reduction could be achieved even in the most pressure-resistant strain of L. monocytogenes by a 6-min application of heat and HHP. Shelf life studies were also conducted, with spoilage levels reached after 5 days of storage at 4 degrees C for controls versus 28 days for treated samples. Sensory evaluation of uninoculated grilled patties showed that panelists could not distinguish between those treated by heat and HHP and untreated controls (P<0.05). Thus, treatment by HHP in combination with mild heating can be used successfully to produce safer, longer-lasting fresh pork without affecting quality.