Effects of Shear Stress Waves on Meat Tenderness: Ultrasonoporation.

Meat is an important part of the food pyramid in Mexico, to such an extent that it is included in the basic food basket. In recent years, there has been great interest in the application of so-called emerging technologies, such as high-intensity ultrasound (HIU), to modify the characteristics of meat and meat products. The advantages of the HIU in meat such as pH, increased water-holding capacity, and antimicrobial activity are well documented and conclusive. However, in terms of meat tenderization, the results are confusing and contradictory, mainly when they focus on three HIU parameters: acoustic intensity, frequency, and application time. This study explores via a texturometer the effect of HIU-generated acoustic cavitation and ultrasonoporation in beef (m. Longissimus dorsi). Loin-steak was ultrasonicated with the following parameters: time tHIU = 30 min/each side; frequency fHIU = 37 kHz; acoustic intensity IHIU = ~6, 7, 16, 28, and 90 W/cm2. The results showed that acoustic cavitation has a chaotic effect on the loin-steak surface and thickness of the rib-eye due to Bjerknes force, generating shear stress waves, and acoustic radiation transmittance via the internal structure of the meat and the modification of the myofibrils, in addition to the collateral effect in which the collagen and pH generated ultrasonoporation. This means that HIU can be beneficial for the tenderization of meat.

Antioxidant and Antimicrobial Activity of Rosemary (Rosmarinus officinalis) and Garlic (Allium sativum) Essential Oils and Chipotle Pepper Oleoresin (Capsicum annum) on Beef Hamburgers.

The inclusion of natural ingredients to preserve meat and meat products has increased in recent years. This study evaluated rosemary (REO) and garlic essential oils (GEO) as well as chipotle pepper oleoresin (CPO), alone or in combination, as preservatives on beef hamburgers (BH). Six treatments were evaluated: T1 (control, without additives), T2 (GEO 1%), T3 (REO 1%), T4 (CPO 0.5%), T5 (GEO 1% + CPO 0.5%) and T6 (REO 1% + CPO 0.5%). The microbiological quality, physicochemical characteristics, sensory evaluation, and lipid oxidation of hamburgers were evaluated. REO, GEO and CPO limited the growth of aerobic microorganisms, S. aureus, Salmonella spp., B. thermosphacta, moulds and yeasts, lactic acid bacteria and coliforms (p < 0.05); however, this effect depended on time. Furthermore, lipid oxidation decreased significantly (p < 0.5) in all treatments, except for T5 (GEO 1% + CPO 0.5%). Regarding sensory acceptance, consumers preferred BH with GEO in terms of colour, odour, flavour and overall appearance (p < 0.05). It is concluded that REO, GEO and CPO, alone or in combination, improve microbiological quality and inhibit the lipid oxidation of BH.

Properties of Oaxaca Cheese Elaborated with Ultrasound-Treated Raw Milk: Physicochemical and Microbiological Parameters.

The effect of ultrasound-treated fresh raw milk upon yield, physicochemical and microbiological quality of Oaxaca cheese was evaluated under a factorial design. The ultrasound frequencies tested were 25 and 45 kHz, during 15 or 30 min. The cheeses made with the ultrasonicated milk (30 min, high-intensity ultrasound, HIU) had greater luminosity without significant changes in hue or chroma, as compared to the controls with no HIU. The yield improved significantly (by up to 2.8 kg/100 L of milk), as the ultrasound treatment time increased. Such cheese yield is attributable to the higher protein content, which was up to 1.5% higher, after sonication. Long-treatment time (30 min) at 25 kHz significantly lowered mesophilic bacteria counts down to limits allowed by current regulations and favors the growth of lactic acid bacteria (LAB) while lowering mold and yeast counts. The absence of E. coli and Salmonella spp. and the decrease in S. aureus counts in Oaxaca cheese were attributed to the mixing of the paste with hot water, inherent to the traditional elaboration process, and to the antagonistic effect of the ultrasound-triggered increased LAB on pathogenic bacteria. Since the artisanal elaboration of Oaxaca cheese does not comply with the current Mexican regulations regarding mesophiles, ultrasound could be a suitable technology to protect its genuine elaboration process with raw milk.

Effect of Packaging and Salt Content and Type on Antioxidant and ACE-Inhibitory Activities in Requeson Cheese.

Requeson cheese is obtained from whey proteins. The production of this cheese is the most economical way to recover and concentrate whey proteins, which is why it is frequently made in some Latin American countries. Four requeson cheese treatments were prepared with different concentrations and combinations of salts (sodium chloride and/or potassium chloride) and were conventionally or vacuum packed. Proteolysis, peptide concentration, angiotensin-converting enzyme (ACE) inhibitory and antioxidant (DPPH and ABTS) activities were evaluated over time (one, seven and fourteen days). Requeson cheese presented antioxidant and ACE inhibitory activities, however, these values vary depending on salt addition, type of packaging and time of storage. The highest values of antioxidant activity (ABTS) were found in cheese added with 1.5% NaCl and 1.5% (NaCl/KCl, 1:1). Cheese without added salt and vacuum packed presented the highest ACE inhibition percentage at day seven. Therefore, it can be concluded that requeson cheese elaborated exclusively of sweet whey, presents antioxidant and ACE inhibition activity. However, for a cheese with ACE inhibitory capacity, it is recommended not to add salts or add at 1% (NaCl) and vacuum pack it. Additionally, for a cheese with antioxidant activity, it is recommended to add salt at 1.5% either NaCl or (1:1) NaCl/KCl and pack it either in a polyethylene bag or vacuum. In conclusion, requeson cheese elaborate with 100% sweet whey is a dairy product with antioxidant and ACE inhibition activity, being low in salt and fat.

Post-mortem ultrasound and freezing of rabbit meat: Effects on the physicochemical quality and weight loss.

High intensity ultrasound (HIU) is a technique with the potential to improve meat quality, however, more research is needed on its application within the chain of cold storage and freezing. This study evaluates the effect of HIU (40 kHz, 9.6 W/cm2, 20 and 40 min) and post-mortem development on the yield and physicochemical quality of rabbit meat in samples treated with HIU pre- and post-storage in a freezer (120 h at -20 °C). Twenty rabbit carcasses were vacuum packed 12 h post-mortem, placed in a fridge at 4 °C for 24 h, and divided in two groups (HIU application before or after freezing), before assigning the treatments. The results show that HIU before freezing produced intense and bright orange-yellow colours, whereas its application after freezing resulted in pale red tones. HIU application accelerates rigor mortis resolution when it is applied before freezing and causes a significant decrease in pH immediately following the HIU treatment. Post-freezing application of HIU is not recommended because it considerably increased weight loss and toughening of the meat when long exposure times were used (40 min). In contrast, a short treatment duration with HIU mitigated the effects of freezing and produced significant increases in water-holding capacity (WHC) after cold storage. The yield (weight loss) of the rabbit meat was not affected when HIU was applied pre-freezing. The application of HIU pre-freezing constitutes a promising technology because it increased the tenderness and the WHC of rabbit meat. However, more research is needed to improve the appearance before scaling up to industrial levels.

Effect of Encapsulated Beet Extracts (Beta vulgaris) Added to Yogurt on the Physicochemical Characteristics and Antioxidant Activity.

Beet has been used as an ingredient for functional foods due to its high antioxidant activity, thanks to the betalains it contains. The effects of the addition of beet extract (liquid and lyophilized) on the physicochemical characteristics, color, antioxidant activity (AA), total betalains (TB), total polyphenols (TP), and total protein concentration (TPC) were evaluated on stirred yogurt. The treatments (T1-yogurt natural, T2-yogurt added with beet juice, T3-added extract of beet encapsulated with maltodextrin, and T4-yogurt added with extract of beet encapsulated with inulin) exhibited results with significant differences (p < 0.05). The highest TB content was observed in T2 (209.49 ± 14.91), followed by T3 (18.65 ± 1.01) and later T4 (12.96 ± 0.55). The highest AA was observed on T2 after 14 days (ABTS˙ 0.819 mM TE/100 g and DPPH˙ 0.343 mM TE/100 g), and the lowest was found on T1 at day 14 (ABTS˙ 0.526 mM TE/100 g and DPPH˙ 0.094 mM TE/100 g). A high content of TP was observed (7.13 to 9.79 mg GAE/g). The TPC varied between 11.38 to 12.56 µg/mL. The addition of beet extract significantly increased AA in yogurt, betalains being the main compounds responsible for that bioactivity.

In vitro assessment of two novel Cellulases from Trabulsiella odontotermitis for agricultural waste utilization.

BACKGROUND: The production of agricultural wastes still growing as a consequence of the population growing. However, the majority of these residues are under-utilized due their chemical composition, which is mainly composed by cellulose. Actually, the search of cellulases with high efficiency to degrade this carbohydrate remains as the challenge. In the present experiment, two genes encoding an endoglucanase (EC 3.2.1.4) and ß-glucosidase (EC 3.2.1.21) were overexpressed in Escherichia coli and their recombinant enzymes (egl-FZYE and cel-FZYE, respectively) characterized. Those genes were found in Trabulsiella odontermitis which was isolated from the gut of termite Heterotermes sp. Additionally, the capability to release sugars from agricultural wastes was evaluated in both enzymes, alone and in combination. RESULTS: The results have shown that optimal pH was 6.0 and 6.5, reaching an activity of 1051.65 ± 47.78 and 607.80 ± 10.19 U/mg at 39 °C, for egl-FZYE and cel-FZYE, respectively. The Km and Vmax for egl-FZYE using CMC as substrate were 11.25 mg/mL and 3921.57 U/mg, respectively, whereas using Avicel were 15.39 mg/mL and 2314.81 U/mg, respectively. The Km and Vmax for cel-FZYE using Avicel as substrate were 11.49 mg/mL and 2105.26 U/mg, respectively, whereas using CMC the enzyme did not had activity. Both enzymes had effect on agricultural wastes, and their effect was improved when they were combined reaching an activity of 955.1 ± 116.1, 4016.8 ± 332 and 1124.2 ± 241 U/mg on corn stover, sorghum stover and pine sawdust, respectively. CONCLUSIONS: Both enzymes were capable of degrading agricultural wastes, and their effectiveness was improved up to 60% of glucose released when combined. In summary, the results of the study demonstrate that the recombinant enzymes exhibit characteristics that indicate their value as potential feed additives and that the enzymes could be used to enhance the degradation of cellulose in the poor-quality forage generally used in ruminant feedstuffs.

Characterization of Beet Root Extract (Beta vulgaris) Encapsulated with Maltodextrin and Inulin.

Betalains are powerful antioxidants contained in beets. These are divided into betacyanins (red-violet) and betaxanthins (yellow-orange), and they can be used as natural colorants in the food industry. The effects of freeze-drying pure beet juice (B) and the encapsulation of beet juice with a dextrose equivalent (DE) 10 maltodextrin (M) and agave inulin (I) as carrier agents were evaluated. The powders showed significant differences (p < 0.05) in all the variables analyzed: water absorption index (WAI), water solubility index (WSI), glass transition temperature (Tg), total betalains (TB), betacyanins (BC), betaxanthins (BX), total polyphenols (TP), antioxidant activity (AA, via 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) (ABTS), and 2,2-diphenyl-1-picrylhydrazyl (DPPH)) and total protein concentration (TPC). The highest values of antioxidant activity were found in the non-encapsulated beet powder, followed by the powder encapsulated with maltodextrin and, to a lesser extent, the powder encapsulated with inulin. The glass transition temperature was 61.63 °C for M and 27.59 °C for I. However, for B it was less than 18.34 °C, which makes handling difficult. Encapsulation of beet extract with maltodextrin and inulin by lyophilization turned out to be an efficient method to increase solubility and diminish hygroscopicity.

Low and High-Intensity Ultrasound in Dairy Products: Applications and Effects on Physicochemical and Microbiological Quality.

Milk and dairy products have a major role in human nutrition, as they contribute essential nutrients for child development. The nutritional properties of dairy products are maintained despite applying traditional processing techniques. Nowadays, so-called emerging technologies have also been implemented for food manufacture and preservation purposes. Low- and high-intensity ultrasounds are among these technologies. Low-intensity ultrasounds have been used to determine, analyze and characterize the physical characteristics of foods, while high-intensity ultrasounds are applied to accelerate particular biological, physical and chemical processes during food product handling and transformation. The objective of this review is to explain the phenomenology of ultrasounds and to detail the differences between low and high-intensity ultrasounds, as well as to present the advantages and disadvantages of each one in terms of the processing, quality and preservation of milk and dairy products. Additionally, it reviews the rheological, physicochemical and microbiological applications in dairy products, such as raw milk, cream, yogurt, butter, ice cream and cheese. Finally, it explains some methodologies for the generation of emulsions, homogenates, crystallization, etc. Currently, low and high-intensity ultrasounds are an active field of study, and they might be promising tools in the dairy industry.

Effect of probiotic cultures on the angiotensin converting enzyme inhibitory activity of whey-based fermented beverages.

Fermented whey-based beverages were elaborated using commercial probiotics cultures (CHR HANSEN): BCT-1®, ABT-4®, ABC where A: Lactobacillus acidophilus, B: Bifidobacterium animalis subsp. lactis, C: Lactobacillus paracasei subsp. paracasei and T: Streptococccus thermophiles. Three treatments were prepared with these probiotics cultures and a treatment without cultures added as a control. All beverage were maintained at 4 °C and evaluated during their shelf life at 0, 7, 14 and 21 days. The variables analyzed were peptide concentration, proteolysis, ACE-inhibitory activity and, peptide and aromatic amino acid profiles. Principal component analysis (PCA) was conducted to assess the relationship between these variables. All whey-based fermented beverages added with probiotics presented ACE inhibitory activity (22-100%). However, whey-based beverage without probiotics added had the highest ACE inhibitory activity (100%), and it was maintained during its shelf life. Fermented beverage with ABT-4® culture had an ACE inhibitory activity from 80 to 100% during its shelf life. Thus can be attributed to the release of peptides during processing. Meanwhile, significative correlations were observed between variables varying this depending on the treatment, both, in magnitude and in direct or inverse direction (0.684-0.986). The ACE inhibitory activity was correlated to proteolysis and peptide and aromatic amino acids profiles. And, the IC50 was observed in the range of 0.01-0.055 mg/mL.

In vitro reduction of methane production by 3-nitro-1-propionic acid is dose-dependent1.

Methanogenesis is a metabolic process that allows the rumen ecosystem the ability to maintain the low hydrogen partial pressures needed for proper digestive function. However, rumen methanogenesis is considered to be an inefficient process because it can result in the loss of 4% to 12% of the total energy consumed by the host. Recent studies have shown that some short-chain nitrocompounds such as nitroethane, 2-nitroethanol, 2-nitro-1-propanol, and 3-nitro-1-propionic acid (3NPA) are capable of inhibiting the production of methane during in vitro culture; nevertheless, optimal supplementation doses have yet to be determined. In the present study, in vitro cultures of freshly collected mixed populations of ruminal microbes were supplemented with the naturally occurring nitrocompound, 3NPA, to achieve 0, 3, 6, 9, or 12 mM. Analysis of fermentation products after 24 h of incubation revealed that methane (CH4) production was reduced in a dose-dependent manner by 29% to 96% (P < 0.05) compared with the amount produced by untreated controls (15.03 ± 0.88 µmol mL-1 incubated liquid). Main effects of the supplement were also observed, which resulted in a reduction (P < 0.05) on amounts of total gas and volatile fatty acids (VFA) produced, as well as in an increase of 0.07 to 0.30 µmol mL-1 on rates of 3NPA degradation. Changes in production of metabolites as CH4, hydrogen (H2), VFA, and NH3 indicated that the fermentation efficiency was not compromised dramatically by 3NPA treatment in moderate doses of 6 and 9 mM. Results further revealed that the metabolism of the 3NPA by microbial populations is also dose-dependent. The microbes were able to metabolize more than 75% of the added nitrocompound, with the greatest degradation rates in cultures treated with 9-mM 3NPA. Finally, from a practical standpoint, and considering the magnitude of CH4 reduction, effect on VFA, and percentage of metabolized supplement, the most efficacious dose for 3NPA administration may be between 3 and 9 mM.

Prevalence of lactic acid bacteria in sliced cooked ham as an indicator of its shelf life / Prevalencia de bacterias de ácido láctico en jamón cocido friccionado como indicador de su vida útil

Background: Ready to eat sliced-cooked-meat-products (RTE) are popular convenience foods. Slicing of such products at retail point is a common practice in supermarkets. Due to handling, as well as the supermarket environment, it has been suggested that the counts and presence of specific lactic acid bacteria (LAB) in these products may be associated with their rapid deterioration and short shelf life. Objectives: The aim was to quantify and identify LAB in commercial sliced cooked ham. Methods: Thirty samples of sliced cooked ham were collected from five supermarkets. Each sample was analyzed in terms of: Lactobacillus on De Man Rogosa, Sharpe agar (30°C), mesophilic (30°C) and thermophilic (37ºC) Streptococcus on M17 agar containing 1% lactose, Lactococcus on LM17 agar containing 100 µg per liter of cycloheximide (25°C) and Enterococci on Kanamicin Aesculin Azide agar containing kanamycin (37°C), all under anaerobic conditions (Gas-Pack System®, BBL) for 48-72h. Twenty-one colonies were randomly picked and physiologically and biochemically characterized. Results: No difference was observed in genuses between supermarkets; however, significant differences were observed between microbial genuses. Enterococci showed the lowest count (2.34 ± 0.05 log10 CFU/g) and Lactobacilli had the highest counts (5.98 ± 0.04 log10 CFU/g). Of the strains isolated 23.8% were identified as thermophillic Lactobacillus, 23.8% mesophilic Lactobacillus, 28.6% Enterococcus, 14.3% Lactococcus and 9.5% Streptococcus. From these, only six could be characterized to species level; one was L.lactis subsp. lactis and five were L. amylolyticus. Conclusions: High LAB counts are a common cause of spoilage in RTE meat products, since these are commonly found in meat environments. Therefore a study on the processing, distribution and in-site handling of RTE meat products at supermarkets may be necessary in order to increase its shelf life.

Antecedentes: Los productos cárnicos rebanados cocidos listos para el consumo (RTE) son alimentos populares de conveniencia. El rebanado de este tipo de productos es una práctica común en los supermercados. Debido a la manipulación, así como al entorno del supermercado, se ha sugerido que los recuentos y la presencia de bacterias ácido lácticas (LAB) en estos productos pueden estar asociados con su rápido deterioro y corta vida en anaquel. Objetivo: El objetivo de este trabajo fue cuantificar e identificar LAB en jamón cocido rebanado en el supermercado. Métodos: se recolectaron 30 muestras de jamón cocido rebanado de cinco supermercados. Cada muestra se analizó en términos de: Lactobacillus en agar De Man Rogosa, Sharpe (30°C), Streptococcus mesofílicos (30°C) y termofílicos (37°C) en agar M17 conteniendo 1% de lactosa, Lactococcus en agar LM17 contiendo 100 µg por litro de ciclohexamida (25°C), y Enterococci en agar Kanamicin Aesculin Azide conteniendo kanamicina (37°C), todos bajo condiciones anaeróbicas (Gas-Pack System®, BBL) por 48-72h. Veintiún colonias seleccionadas al azar fueron fisiológica y bioquímicamente caracterizadas. Resultados: No se observaron diferencias en el género entre los supermercados; sin embargo, se observaron diferencias significativas entre género microbiano. Los enterococos mostraron los recuentos más bajos (2,34 ± 0,05 log10 CFU/g) y los lactobacilos los más altos (5,98 ± 0,04 log10 CFU/g). De las cepas aisladas 23,8% fueron identificados como Lactobacillus termófilos, 23,8% Lactobacillus mesófilos, 28,6% Enterococcus, 14,3% Lactococcus y 9,5% Streptococcus. De éstos, sólo seis pudieron caracterizarse a nivel de especie; uno fue L.lactis subsp lactis y cinco fueron L. amylolyticus. Conclusiones: Conteos altos de LAB son una causa común del deterioro de los productos cárnicos listos para el consumo, ya que estos se encuentran comúnmente en los entornos donde se maneja carne. Por lo tanto, es necesario llevar a cabo un estudio sobre el procesamiento, distribución y manejo de productos cárnicos listos para el consumo en los supermercados con el fin de aumentar su vida en anaquel.

Draft Genome Sequences for Five Strains of Trabulsiella odontotermitis, Isolated from Heterotermes sp. Termite Gut.

Trabulsiella odontotermitis represents a novel species in the genus Trabulsiella with no complete genome reported yet. Here, we describe the draft genome sequences of five isolates from termites present in the north of Mexico, which have an interesting pool of genes related to cellulose degradation with biotechnological application.

Genome Sequence of Citrobacter sp. CtB7.12, Isolated from the Gut of the Desert Subterranean Termite Heterotermes aureus.

The draft genome of Citrobacter sp. CtB7.12, isolated from termite gut, is presented here. This organism has been reported as a cellulolytic bacterium, which is biotechnologically important because it can be used as a gene donor for the ethanol and biofuel industries.