Laura K. Jefferies

Effect of Micronutrient Fortification on Nutritional and Other Properties of Nixtamal Tortillas

ABSTRACT Nixtamalization is the process of steeping dried corn in hot water with calcium hydroxide (lime) with subsequent removal of all or most of the pericarp through washing. The resulting product is called nixtamal. Approximately 60% of corn tortillas in Mexico are produced from nixtamal, with the remainder prepared from nixtamalized corn flour. Nixtamal was fortified with micronutrient premix containing iron, zinc, folic acid, niacin, riboflavin, and thiamin. Premix composition followed a proposed Mexican regulation for corn flour fortification, adjusted for moisture. Effects of premix on masa adhesiveness, hardness, and pH, as well as tortilla sensory properties, stretchability, rollability, and color were measured. Micronutrient levels were tested in the dry corn, nixtamal, masa, and tortillas. There were no significant differences in masa texture or pH, tortilla rollability, or consumer acceptance of tortillas when comparing unfortified control and fortified treatments. Added thiamin was almost en...

Effect of Iron Source on Color and Appearance of Micronutrient-Fortified Corn Flour Tortillas

ABSTRACT Iron deficiency anemia is a widespread occurrence. Consequently, iron is commonly added in cereal fortification programs. However, many iron sources cause undesirable sensory changes, especially color changes, in the food being fortified. This study evaluated the effect of different iron sources on CIE L*a*b* color values and sensory color perception in fortified corn tortillas. Corn masa flour was fortified with micronutrient premix containing vitamins, zinc, and one of eight iron compounds. Iron sources included ferrous fumarate (F), ferrous sulfate (S), ferric orthophosphate (OP), ferrous lactate (L), ferrous gluconate (G), ferric pyrophosphate (PP), sodium iron (III)-EDTA, and A-131 electrolytic iron (E), with addition levels adjusted based on bioavailability. Control (Ct) samples were prepared with all micronutrients except iron. All iron-fortified tortillas had lower L* values and were significantly darker than control tortillas. Based on instrumental color values and Mexican regulatory rec...

Sensory and Nutritional Quality of Split Peas (Pisum Sativum) Stored up to 34 Y in Residential Storage

The sensory and nutritional quality of split peas stored up to 34 y was determined. Nine samples of split peas representing 5 retail brands packaged in Nr 10 cans and stored at room temperature were obtained from donors. Duplicate cans of a fresh sample of split peas were purchased as controls. Can head space oxygen ranged from 0.255% to 20.1%. Water activity of the raw split peas ranged from 0.41 to 0.56. The green color of the raw split peas decreased over time as shown by increasing CIE a* values. Flavor, appearance, texture, and overall liking hedonic scores (9-point scale) of split-pea soup made from each sample ranged from 3.7 to 6.7 and decreased over time. Hedonic scores for appearance were correlated with the decrease in raw product green color (r(2)= 0.65). Hedonic scores for soup texture declined over time, which corresponded with increasing hardness of the cooked peas as measured by a TA.XT2 texture analyzer. All samples were judged to be acceptable in an emergency situation by over 75% of sensory panelists. Available thiamin was significantly lower in older samples while riboflavin remained unchanged. The results indicate that split pea quality declines over time, but the product maintains sufficient sensory acceptance to be considered for potential use in emergency storage and other applications where minimal stock rotation is a common practice.

Isolation and characterization of the microflora of nixtamalized corn masa.

Corn tortillas are a staple in the diet among the Mexican population, and are traditionally produced through a process known as nixtamalization. This traditional process involves steeping whole-kernel corn in an alkaline solution overnight and then grinding the corn into dough (masa), which is then baked. While the masa is held before baking, significant microbial change can occur which leads to fermentation and spoilage. The objective of this research was to characterize and identify the microflora of nixtamalized corn masa from six different commercial tortilla mills throughout Guadalajara, Mexico. The identification of samples was conducted using the microbial identification system (MIS), which analyzes cellular fatty acids via gas chromatography to identify bacterial species. Lactic acid bacteria and aerobic mesophiles were the predominant organisms, with both groups having counts ranging from 10(4) to 10(7)cfu/g across all mills. Coliform populations were observed at counts of 10(2) to 10(3)cfu/g, while yeast and mold counts were typically less than 10(1)cfu/g. Some mills showed no presence of coliforms or yeast or mold. Streptococcus bovis and Lactobacillus oris were isolated from all mills, and were the most prevalent organisms representing 43% and 17% of all lactic acid bacteria isolated, respectively. S. bovis was also isolated on the aerobic tryptic soy plates and was the most prevalent species representing 19% of the total organisms from these aerobic plates.

Translocation and cross-contamination of E. coli O157 in beef eye-of-round subprimal cuts processed with high-pressure needleless injection.

UNLABELLED High-pressure needleless injection (HPNI) is an emerging enhancing process where small-diameter, high-velocity bursts of liquid penetrate soft foods at pressures up to 69 MPa. The incidence and depth of translocated surface-inoculated E. coli O157 in HPNI-processed beef eye-of-round subprimal cuts was determined. HPNI translocated E. coli O157 from the surface to the interior of the eye-of-round subprimal cuts with incidence of 40% (± 7%), 25% (± 8%), and 25% (± 8)% for subprimals that had been surface-inoculated with a 4-strain cocktail at 0.5, 1, and 2 log₁₀ CFU/cm² , respectively. The run-off water was collected and found to contain 2, 2, and 3 log₁₀ CFU/mL E. coli O157. The runoff was reused for HPNI of additional subprimals, and this resulted in a cross-contamination incidence of 83% (± 4%), 60% (± 15%), and 37% (± 6)%. Incidence of translocation and cross-contamination was similar at 0 to 1, 1 to 2, 2 to 3, 3 to 4, 4 to 6, and 6 to 8 cm below the inoculated surface. Results indicate that surface microbiota on beef will be carried to the interior of HPNI-processed beef by initial translocation from the surface with the injected fluid and by cross-contamination with recycled fluid. PRACTICAL APPLICATION This research has practical relevance for the beef enhancement process called high-pressure needleless injection. The processs effect on surface bacteria on beef was studied.

Inhibition of Clostridium Perfringens Growth During Extended Cooling of Cooked Uncured Roast Turkey and Roast Beef Using a Concentrated Buffered Vinegar Product and a Buffered Vinegar Product

This research was conducted to evaluate the effectiveness of a concentrated buffered vinegar product (CBV) and a simple buffered vinegar product (BV) for controlling Clostridium perfringens outgrowth during extended cooling times of ready-to-eat roast turkey and roast beef. Whole turkey breasts and beef inside rounds were injected with a typical brine and then ground and mixed with CBV (0.0, 2.01, 2.70, and 3.30% [w/w]) or BV (0.0, 1.75, 2.25, and 3.75% [w/w]) and a three-strain C. perfringens spore cocktail to a detectable level of ca. 2 to 3 log CFU/g. The meat was divided into 10-g portions, vacuum packaged, and stored frozen until tested. The turkey and beef were cooked in a programmable water bath to 71.6°C (160.8°F) in 5 h and to 57.2°C (135°F) in 6 h, respectively. The cooked turkey and beef were then cooled exponentially from 48.9 to 12.8°C (120 and 55°F) in 6, 9, 12, 15, and 18 h for the five cooling treatments. The cooling continued until the temperature reached 4.4°C (40°F). C. perfringens counts were determined at 54.4°C (130°F) and 4.4°C. CBV at 2.01% effectively limited C. perfringens growth in turkey to ≤1 log CFU/g with up to a 9-h cooling treatment, and 2.70 and 3.30% solutions were effective with up to the 18-h cooling treatment. BV had an inhibitory effect on C. perfringens outgrowth in beef but did not limit growth to ≤1 log CFU/g at any concentration tested for any of the cooling treatments.