Oregano powder substitution and shelf life in pork chorizo using Mexican oregano essential oil

Abstract The aim of this study was to evaluate the effect of oregano essential oil (MOO) from Mexican oregano, Lippia berlandieri Schauer, as substitute for Mexican oregano powder (MOP) on pork chorizo physicochemical characteristics, texture, antioxidant capacity, aerobic bacteria colony counts, and sensory evaluation under storage conditions over 7 d. The treatments were T1 = chorizo + 0.1% MOP and T2 = chorizo + 0.1% MOO. The pH, redness (a*), yellowness (b*), Chroma, and browning index (BI) were affected by treatments and storage time. T2 presented lower pH (5.27) at d 1 than at d 7 (5.34), as well as a* (23.13 vs. 25.27), b* (14.85 vs. 17.45), Chroma (28.60 vs. 30.79), and BI (103.42 vs. 109.82) were higher at d 7. At d 1, hardness (1392.75 vs. 872.29 g), springiness (0.3675 vs. 0.3351 mm), gumminess (491.45 vs. 284.38 g), and chewiness (180.25 vs. 95.43 g mm) were higher in T1 than T2. Aerobic bacteria counts (T1—4.19 vs. 4.73 log CFU/g and T2—4.37 vs. 4.50 log CFU/g, respectively) increased within each treatment at d 7. Antioxidant capacity was not affected (26.48 and 27.42%). Oregano odor was different at 7 d with T2 having a stronger odor (5.70) than T1 with oregano powder (4.63). Mexican oregano essential oil in the pork chorizo formulation improved pH, color parameters, textural profile, and sensory characteristics.


| INTRODUC TI ON
Pork meat is an important component in the human diet and is a major commodity in the meat industry for the manufacture of sausage, ham, and chorizo. Chorizo is a raw sausage composed of beef, pork meat and fat, additives, and spices that give it its characteristic flavor (Porcella et al., 2001). Chorizo preparation is still basically a family art employing techniques requiring rudimentary utensils and natural casings. The sausages are hand-kneaded and stuffed without any aseptic measures being taken (González & Díez, 2002).
In Mexico, chorizo is commonly manufactured from pork meat and is classified as a fresh sausage product and comes in a variety of formulations and manufacture. This Mexican product has a pork meat content of 70%-80% and back fat content of 15%-20%. The color of Mexican chorizo is characteristically red and is seasoned with spices, salt, oregano powder, and vinegar.
Consumers today want foods containing healthy ingredients that have good composition and an extended shelf life accompanied by | 1255 PERALES-JASSO Et AL. minimal deterioration in components and sensory characteristics.
The aim of this study was to evaluate the effect of a plant extract, oregano essential oil from Mexican oregano, Lippia berlandieri Schauer, as substitute for Mexican oregano powder on pork chorizo formulation and effects on preservation of physicochemical, textural, microbiological, antioxidant, and sensory characteristics during storage.

| Experimental design
A random complete design of two treatments was carried out in which Mexican oregano powder was replaced by essential oil from

| Chorizo preparation
Each treatment was formulated in two replicates of 2.0 kg each. The formulation was established according to González and Díez (2002), with some variation. The formulation (w/w) consisted of 75.0% lean pork meat, 18.0% pork back fat, 2.2% guajillo chili pepper powder, 0.1% paprika powder, 0.1% Mexican oregano powder, 0.5% garlic powder, 1.7% NaCl, and 2.4% acetic acid (white vinegar; Clemente Jacques, Sabormex S.A. de C.V., Mexico City, Mexico). The meat and pork back fat, maintained at 4.0°C, were ground through a 3/8-in (9.5mm) grind plate using a TORREY ® grinder (Model MV-22R-SS; Grupo Torrey, S.A. de C.V., Nuevo Leon, Mexico). Next, powder ingredients were added and mixed manually for 8 min into the ground meat. For the treatment T2 preparation, MOO was added in place of the MOP. The chorizo links were stored at 4.0°C for evaluation at 1 and 7 d.

| Physicochemical analysis
The pork chorizo pH was determined with a puncture electrode (Orion and browning index (BI) were estimated according to Ledesma et al. (2016). The pH and color were measured in triplicate at four sections of the chorizo for each replicate per treatment (n = 24 per treatment).
The colorimeter was standardized and calibrated using a white plate.

| Shear force (SF) and texture profile analyses (TPA)
The SF and TPA of the chorizo were determined at 4°C with a TA.XT Plus texturometer (Stable Micro Systems, Surrey, UK) in eight sections per replicate of chorizo (two replicates per treatment; n = 16 per treatment). The SF was performed using a Warner-Bratzler shear blade with a triangular slot cutting edge. Ten cylindrical segments (3.0 cm diameter × 4.5 cm long) were used to evaluate the SF.
The test conditions used in the instrument were a velocity of 2 mm/s pretest, 2 mm/s during the test, 10 mm/s post-test, and a distance of 40 mm. The SF value was taken from the maximum point of the curve obtained from the test.
The TPA was determined in eight standardized cylinders per replicate (3.0 cm diameter × 2.5 cm high). A cylindrical piston (75 mm in diameter) was used to compress the sample during two test cycles, compressing the sample up to 60% from the original height within a time span of 5 s between cycles. Force-time curves of deformation were obtained from the conditions established in the texturometer.

| Microbiological analysis
Microbiological counts were carried out according to Casquete et al. (2012) andNOM-110-SSA1 (1994) in triplicate on two sections at 1 and 7 d per replicate (n = 6 per treatment per day). A total of 10 g per sample were collected aseptically, transferred to sterile polyethylene bags to which was added 90 ml of sterile phosphate buffer (pH 6.5). Each sample was subjected to three 1.5-min mixing cycles in a Stomacher

| Sensory evaluation
An affective sensory test of attributes was conducted at 1 and 7 d of storage to measure the level satisfaction of 30 consumers. Each consumer evaluated two chorizo slices (6 mm thickness) chosen at random. Samples for evaluation were maintained at 4°C and were presented on plastic Petri dishes. The attributes evaluated were red color, oregano odor, appearance, smoothness, and overall accept-

| Statistical analysis
An analysis of variance was performed using the proc GLM of SAS (2006) and the next model statistical: where y ijk = physicochemical, textural, microbiological, antioxidant, and sensory variables evaluated over time; μ = general media; Ƭ i = fixed effect of i-th treatment (T1 and T2); δ j = effect of j-th evaluation day (1 and 7 d); (Ƭδ) ij = effect of the interaction between the i-th treatment and the j-th day; Ԑ ijk = random error normally independently distributed with media of zero and variance σ 2 [Ԑ ijk ~ NID (0, σ 2 )]. The statistical model of sensorial analysis considered a complete random block design, where each consumer was the block effect (β j ) in each period. A significance level of p < .05 was used to assess significant differences between treatment means, days, and interaction. When the fixed effects and its interaction had significant effect, the means were compared using Adjust = Tukey (SAS 2006). Table 1 shows the pH and color parameters of pork chorizo at 1 and 7 d. The pH, redness (a*), yellowness (b*), saturation index (Chroma), and browning index (BI) were affected statistically (p < .05) by the treatments and days of storage. At d 1, the pH was lower in T2 than in T1, however, was not different at d 7.

| Physicochemical analysis
Measurements of a* were different statistically (p < .05) at d 7 with a* for T2 being higher than in T1, as well as higher than T1 and T2 at d 1. Values for b*, Chroma, and BI were also higher at d 7 for T2 compared to T1. L*, Hue angle, and ∆E were not influenced statistically (p > .05) by treatments at each time and within treatments on different days. These results could indicate that 0.1% MOO can improve the chorizo color, because color variables presented high values in T2.

| Microbiological analysis and antioxidant capacity
Microbial analysis and antioxidant capacity results of pork chorizo are presented in Table 3. Mesophyll counts were not different statistically between treatments (p > .05), but there was an effect (p < .05) with storage days, with values for T1 and T2, respectively, being higher at d 7 than at d 1. Treatments had no statistical effect (p > .05) on DPPH; however, pork chorizo treated with MOO (T2) had a slightly higher mean value compared to the control (T1).
TA B L E 1 Physicochemical parameters of pork chorizo sausage following treatment with Mexican oregano powder and Lippia berlandieri Schauer oregano essential oil and storage at 1 and 7 d

| Sensory evaluation
The attributes of sensory evaluation were affected by treatments (p < .05) at 7 d only (Table 4), with T2 presenting a stronger oregano odor. Color, appearance, smoothness, and overall acceptability did not present differences (p > .05) between treatments and storage times.

| Physicochemical analysis
The pH result obtained at d 1 and 7 may be attributed to the MOO pH (4.49 ± 0.05), because oregano powder pH was higher (6.28 ± 0.02). Salgado et al. (2006) reported lower pH values in onion chorizo than those reported here, while Bozkurt and Bayram (2006) obtained similar values in respect to this study with 0.1% MOO from Lippia berlandieri Schauer. On the other hand, at d 7, Bozkurt and Bayram (2006) obtained similar values for L*, ∆E, and BI, but lower values for a* and b* of the spicy sausage sucuk during ripening. These authors indicated that the color is the most important quality attribute of sucuk, as it influences consumer acceptability. Therefore, the results presented for a* (significant), L*, Hue, and ∆CT (not significant) when MOO was used could indicate that MOO can be used to maintain the redness of pork chorizo, as well as to maintain lightness, saturation, and color change, potentially enhancing consumer preference.
Finally, similar results for pH and color were obtained by Lorenzo, González-Rodríguez, Sánchez, Amado, and Franco (2013) at d 20 of storage when examining the effects of 1 g/kg of grape seed or chestnut extract in cured chorizo sausage.

| Shear force (SF) and texture profile analyses (TPA)
A possible accelerated change in the product structure over time in T1 could explain a low SF value at d 7. The TPA results suggest that Lippia berlandieri Schauer MOO can be used to conserve the chorizo texture during storage, without changes in product structure over time. Lorenzo et al. (2013) found at d 7 similar values in hardness, springiness, chewiness, and gumminess when testing 1 g/kg of grape seed or chestnut extract in cured chorizo sausage,

| Microbiological analysis and antioxidant capacity
With respect to microbial evaluation in pork chorizo in the current study, Porcella et al. (2001)  TA B L E 3 Microbiological analysis and antioxidant capacity of pork chorizo sausage following treatment with Mexican oregano powder and Lippia berlandieri Schauer oregano essential oil and storage at 1 and 7 d The search for alternative methods to retard oxidative processes in meat has led to research with alternative natural antioxidants (Broncano et al., 2012). In the current study, MOO was used in chorizo as a natural preserver followed by an evaluation its effect in the shelf life. It is possible that the differences found in antioxidant capacity were due to antioxidant activity of the total phenolic (e.g., carvacrol and thymol) content of MOO (García-

| Sensory evaluation
In contrast to the oregano odor obtained in pork chorizo, García-  Lorenzo et al. (2013) found no differences for color, aroma, rancidness, taste, and overall acceptability in dry-cured sausages with natural extracts. Furthermore, they showed that the addition of grape seed extract (1 g/kg) as a natural antioxidant improved the acceptability of dry-cured sausages. This could explain the oregano odor acceptability in the treatment with Mexican oregano oil that improved this sensory property. Furthermore, the stability found with color, appearance, smoothness, and acceptability could be considered stable because T2 (MOO) was not different from T1 (control) at 7 d of storage.

| CON CLUS IONS
Essential oil (0.1%) of Mexican oregano, Lippia berlandieri Schauer, in chorizo formulation improved color parameters, especially red color, browning index, textural profile analysis, and sensory characteristics. Additionally, the mesophilic microbial counts were similar for the two treatments following storage for 7 d. Results of this study demonstrate the potential usefulness of Lippia berlandieri Schauer MOO to enhance quality, sensory characteristics, and shelf life of pork chorizo sausage.

CO N FLI C T O F I NTE R E S T
The authors declare that there is no conflict of interests. T1: chorizo + 0.1% Mexican oregano powder; T2: chorizo + 0.1% Lippia berlandieri Schauer oregano essential oil; SEM, standard error of means; RMSE, root-mean-square error; Ƭ i , fixed effect of i-th treatment (T1 and T2); δ j : effect of j-th evaluation day (1 and 7 d); (Ƭδ) ij : effect of the interaction between the i-th treatment and the j-th day. Means (n = 30) within the same column and within each treatment and at different times with different superscripts (lower case) differ significantly when the p-value of (Ƭ j ) <.05. Means (n = 30) within the same column, for all treatments and for all days, with different superscripts (upper case) differ significantly when the p-value of (Ƭδ) ij <.05.