Bactericidal activity of lauric arginate in milk and Queso Fresco cheese against Listeria monocytogenes cold growth

Lauric arginate (LAE) at concentrations of 200 ppm and 800 ppm was evaluated for its effectiveness in reducing cold growth of Listeria monocytogenes in whole milk, skim milk, and Queso Fresco cheese (QFC) at 4°C for 15 to 28 d. Use of 200 ppm of LAE reduced 4 log cfu/mL of L. monocytogenes to a nondetectable level within 30 min at 4°C in tryptic soy broth. In contrast, when 4 log cfu/mL of L. monocytogenes was inoculated in whole milk or skim milk, the reduction of L. monocytogenes was approximately 1 log cfu/mL after 24 h with 200 ppm of LAE. When 800 ppm of LAE was added to whole or skim milk, the initial 4 log cfu/mL of L. monocytogenes was nondetectable following 24 h, and no growth of L. monocytogenes was observed for 15 d at 4°C. With surface treatment of 200 or 800 ppm of LAE on vacuum-packaged QFC, the reductions of L. monocytogenes within 24 h at 4°C were 1.2 and 3.0 log cfu/g, respectively. In addition, the overall growth of L. monocytogenes in QFC was decreased by 0.3 to 2.6 and by 2.3 to 5.0 log cfu/g with 200 and 800 ppm of LAE, respectively, compared with untreated controls over 28 d at 4°C. Sensory tests revealed that consumers could not determine a difference between QFC samples that were treated with 0 and 200 ppm of LAE, the FDA-approved level of LAE use in foods. In addition, no differences existed between treatments with respect to flavor, texture, and overall acceptability of the QFC. Lauric arginate shows promise for potential use in QFC because it exerts initial bactericidal activity against L. monocytogenes at 4°C without affecting sensory quality.     

Enhanced extraction of flavanones hesperidin and narirutin from Citrus unshiu peel using subcritical water

Flavanones including hesperidin and narirutin constitute the majority of the flavonoids that occur naturally in citrus fruits. The main purpose of this study was to extract valuable natural flavanones from agricultural by-products such as citrus peels using subcritical water extraction (SWE). Thus, the application of SWE to extraction of flavanones hesperidin and narirutin from Citrus unshiu peel was evaluated, and the effect of key operating conditions was determined by varying the extraction temperature (110–200 °C) and time (5–20 min) under high pressure (100 ± 10 atm). The maximum yields of hesperidin (72 ± 5 mg/g C. unshiu peel) and narirutin (11.7 ± 0.8 mg/g C. unshiu peel) were obtained at an extraction temperature of 160 °C for an extraction time of only 10 min. These yields accounted for approximately 99% of the total amount of these flavanones in the original material. The SWE was compared with three conventional extraction methods in terms of the extraction time and recovery yields for hesperidin and narirutin. The hesperidin yield by SWE was more than 1.9-, 3.2-, and 34.2-fold higher than those obtained by extraction methods using ethanol, methanol, or hot water, respectively, and the narirutin yield was more than 1.2-, 1.5-, and 3.7-fold higher.     

Antioxidant and antibacterial activities of Nephelium lappaceum L. extracts

Ether, methanolic and aqueous extracts of lyophilized rambutan (Nephelium lappaceum L.) peels and seeds were evaluated for phenolic contents, antioxidant and antibacterial activities. High amounts of phenolic compounds were found in the peel extracts and the highest content was in the methanolic fraction (542.2 mg/g dry extract). Several potential antioxidant activities, including reducing power, β-carotene bleaching, linoleic peroxidation and free radical scavenging activity, were evaluated. The peel extracts exhibited higher antioxidant activity than the seed extracts in all methods determined (P < 0.05). The methanolic fraction was found to be the most active antioxidant as shown by their 50% DPPH inhibition concentration, 4.94 μg/mL. The results indicated this fraction exhibited greater DPPH radical scavenging activity than BHT and ascorbic acid (0.32 g dry extract/g BHT or ascorbic acid). Antibacterial activity against eight bacterial strains was assessed by disc diffusion and broth macrodilution methods. All peel extracts exhibited antibacterial activity against five pathogenic bacteria. The most sensitive strain, Staphylococcus epidermidis, was inhibited by the methanolic extract (MIC 2.0 mg/mL).     

Combined antimicrobial effect of oregano essential oil and caprylic acid in minced beef

Oregano essential oil (OEO) and caprylic acid (CA) are highly aromatic natural antimicrobials with limited individual application in food. We proved their combined additive effect when used in meat. Application of 0.5% CA and 0.2% OEO (v/w) with 0.1% of citric acid in vacuum packed minced beef inoculated with Listeria monocytogenes at a concentration of 5 log cells/g reduced counts of lactic acid bacteria by 1.5 log CFU/g and counts of psychrotrophic bacteria and L. monocytogenes by more than 2.5 log CFU/g at the end of storage at 3 °C for 10 days. In sensory evaluation the samples with OEO showed during the whole experiment statistically better scores than control, whereas the samples treated with CA showed worse colour attributes.     

Antimicrobial activity of nisin, reuterin, and the lactoperoxidase system on Listeria monocytogenes and Staphylococcus aureus in cuajada, a semisolid dairy product manufactured in Spain

The inhibitory activity of nisin (N), reuterin (R), and the lactoperoxidase system (LPS), added individually or in combination, against Listeria monocytogenes and Staphylococcus aureus was investigated in “cuajada” (curdled milk), a semisolid dairy product manufactured in Spain. Cuajada was manufactured from UHT skim milk separately inoculated with L. monocytogenes and Staph. aureus, each at approximately 4 log cfu/mL, and held under conditions of temperature abuse (10°C). On d 3, a synergistic bactericidal activity was observed for the combinations of biopreservatives assayed, with L. monocytogenes counts of only 0.30 log cfu/mL in cuajada made with N + R + LPS vs. 8.31 log cfu/mL in control cuajada. After 12 d, L. monocytogenes could not be detected in cuajada made with added N + LPS or N + R + LPS. Staphylococcus aureus was more resistant than L. monocytogenes to biopreservatives added individually. On d 3, the synergistic effect of the 3 biopreservatives against Staph. aureus resulted in counts of 3.03 log cfu/mL in cuajada made with N + R + LPS vs. 6.40 in control cuajada. After 12 d, Staph. aureus counts were 2.61 log cfu/mL in cuajada made with N + R + LPS, whereas they ranged from 6.11 to 7.70 log cfu/mL in control cuajada and in cuajada made with other combinations of biopreservatives. The most pronounced decrease in pathogen counts was achieved by the triple combination N + R + LPS, which acted synergistically on the inactivation of L. monocytogenes and Staph. aureus in cuajada over 12 d at 10°C. The treatment combining these 3 natural biopreservatives at low concentrations, within the hurdle concept of food preservation, might be a useful tool to control the growth of pathogenic microorganisms in nonacidified dairy products.     

Evaluation of the effects of ultraviolet light on bacterial contaminants inoculated into whole milk and colostrum,and on colostrum immunoglobulin G

Raw milk and colostrum can harbor dangerous microorganisms that can pose serious health risks for animals and humans. According to the USDA, more than 58% of calves in the United States are fed unpasteurized milk. The aim of this study was to evaluate the effect of UV light on reduction of bacteria in milk and colostrum, and on colostrum IgG. A pilot-scale UV light continuous (UVC) flow-through unit (45 J/cm²) was used to treat milk and colostrum. Colostrum and sterile whole milk were inoculated with Listeria innocua, Mycobacterium smegmatis, Salmonella serovar Typhimurium, Escherichia coli, Staphylococcus aureus, Streptococcus agalactiae, and Acinetobacter baumannii before being treated with UVC. During UVC treatment, samples were collected at 5 time points and bacteria were enumerated using selective media. The effect of UVC on IgG was evaluated using raw colostrum from a nearby dairy farm without the addition of bacteria. For each colostrum batch, samples were collected at several different time points and IgG was measured using ELISA. The UVC treatment of milk resulted in a significant final count (log cfu/mL) reduction of Listeria monocytogenes (3.2 ± 0.3 log cfu/mL reduction), Salmonella spp. (3.7 ± 0.2 log cfu/mL reduction), Escherichia coli (2.8 ± 0.2 log cfu/mL reduction), Staph. aureus (3.4 ± 0.3 log cfu/mL reduction), Streptococcus spp. (3.4 ± 0.4 log cfu/mL reduction), and A. baumannii (2.8 ± 0.2 log cfu/mL reduction). The UVC treatment of milk did not result in a significant final count (log cfu/mL) reduction for M. smegmatis (1.8 ± 0.5 log cfu/mL reduction). The UVC treatment of colostrum was significantly associated with a final reduction of bacterial count (log cfu/mL) of Listeria spp. (1.4 ± 0.3 log cfu/mL reduction), Salmonella spp. (1.0 ± 0.2 log cfu/mL reduction), and Acinetobacter spp. (1.1 ± 0.3 log cfu/mL reduction), but not of E. coli (0.5 ± 0.3 log cfu/mL reduction), Strep. agalactiae (0.8 ± 0.2 log cfu/mL reduction), and Staph. aureus (0.4 ± 0.2 log cfu/mL reduction). The UVC treatment of colostrum significantly decreased the IgG concentration, with an observed final mean IgG reduction of approximately 50%. Development of new methods to reduce bacterial contaminants in colostrum must take into consideration the barriers imposed by its opacity and organic components, and account for the incidental damage to IgG caused by manipulating colostrum.     

Fat content increases the lethality of ultra-high-pressure homogenization on Listeria monocytogenes in milk

Listeria monocytogenes CCUG 15526 was inoculated at a concentration of approximately 7.0 log₁₀ cfu/mL in milk samples with 0.3, 3.6, 10, and 15% fat contents. Milk samples with 0.3 and 3.6% fat content were also inoculated with a lower load of approximately 3.0 log₁₀ cfu/mL. Inoculated milk samples were subjected to a single cycle of ultra-high-pressure homogenization (UHPH) treatment at 200, 300, and 400 MPa. Microbiological analyses were performed 2 h after the UHPH treatments and after 5, 8, and 15 d of storage at 4°C. Maximum lethality values were observed in samples treated at 400 MPa with 15 and 10% fat (7.95 and 7.46 log₁₀ cfu/mL), respectively. However, in skimmed and 3.6% fat milk samples, complete inactivation was not achieved and, during the subsequent 15 d of storage at 4°C, L. monocytogenes was able to recover and replicate until achieving initial counts. In milk samples with 10 and 15% fat, L. monocytogenes recovered to the level of initial counts only in the milk samples treated at 200 MPa but not in the milk samples treated at 300 and 400 MPa. When the load of L. monocytogenes was approximately 3.0 log₁₀ cfu/mL in milk samples with 0.3 and 3.6% fat, complete inactivation was not achieved and L. monocytogenes was able to recover and grow during the subsequent cold storage. Fat content increased the maximum temperature reached during UHPH treatment; this could have contributed to the lethal effect achieved, but the amount of fat of the milk had a stronger effect than the temperature on obtaining a higher death rate of L. monocytogenes.     

Isolation and characterization of a novel analyte from Bacillus subtilis SC-8 antagonistic to Bacillus cereus

In this study, an effective substance was isolated from Bacillus subtilis SC-8, which was obtained from traditionally fermented soybean paste, cheonggukjang. The substance was purified by HPLC, and its properties were analyzed. It had an adequate antagonistic effect on Bacilluscereus, and its spectrum of activity was narrow. When tested on several gram-negative and gram-positive foodborne pathogenic bacteria such as Salmonella enterica, Salmonella enteritidis, Staphylococcus aureus, and Listeria monocytogenes, no antagonistic effect was observed. Applying the derivative from B. subtilis SC-8 within the same genus did not inhibit the growth of major soybean-fermenting bacteria such as Bacillus subtilis, Bacillus licheniformis, and Bacillus amyloquefaciens. The range of pH stability of the purified antagonistic substance was wide (from 4.0 to >10.0), and the substance was thermally stable up to 60 °C. In the various enzyme treatments, the antagonistic activity of the purified substance was reduced with proteinase K, protease, and lipase; its activity was partially destroyed with esterase. Spores of B. cereus did not grow at all in the presence of 5 μg/mL of the purified antagonistic substance. The isolated antagonistic substance was thought to be an antibiotic-like lipopeptidal compound and was tentatively named BSAP-254 because it absorbed to UV radiation at 254 nm.     

Novel approach to decontaminate food-packaging from pathogens in non-thermal and not chemical way: Chlorophyllin-based photosensitization

This study was focused on the possibility to inactivate main food pathogens, their spores and biofilms on the surface of packaging material polyolefine by Na-chlorophyllin (Na-Chl)-based photosensitization and to compare efficiency of this treatment with conventional antimicrobials.Data indicate that Bacillus cereus and Listeria monocytogenes were effectively inactivated (7 log) by Na-Chl (7.5 × 10⁻⁷ M)-based photosensitization in vitro and on the surface of packaging. Meanwhile to achieve adequate inactivation of thermo-resistant strains, spores or biofilms the higher Na-Chl concentration and longer illumination times had to be used. Comparison of different surface decontamination treatments reveal that photosensitization is much more effective against B. cereus and L. monocytogenes attached on the surface than washing with water or 200 ppm Na-hypochlorite.Our data support the idea that photosensitization may serve in the future for the development of human and environment friendly, non-thermal surface decontamination technique.     

Potential production and preservation of dahi by Lactococcus lactis W8, a nisin-producing strain

Lactococcus lactis W8 produced nisin concomitantly while fermenting milk to “dahi”, a traditional Indian fermented milk. The activity of nisin was detected at 3 h of fermentation, which increased in parallel to growth of the organism and reached its maximum at 6 h. The activity remained essentially stable thereafter. At 7 h of fermentation of milk with the strain L. lactis W8 the pH of the medium dropped to 4.2, when the milk became converted to dahi. The produced dahi displayed antibacterial property against spoilage and pathogenic bacteria including Listeria monocytogenes. When L. monocytogenes was mixed with dahi at 5.2 log CFU/ml and stored at 4 °C, the number of L. monocytogenes gradually decreased and became undetectable at 10 h. L. lactis W8 appeared to be a suitable starter culture for production of dahi from milk and preservation of the dahi.     

Antioxidative and anti-inflammatory properties of Citrus sulcata extracts

Citrus sulcata was subjected to ultrasound, high-pressure, and Soxhlet extractions. The antioxidant and anti-inflammatory activities of the extracts were evaluated qualitatively and quantitatively. The antioxidant content of the peel extract was twice that of the fruit extract. The quantitative analysis showed that the narirutin and hesperidin contents in the peel extracts were 8.8 and 7.5 mg/100 g, respectively. These extracts had a total phenolic content of 112.22 ± 2.89 gallic acid equivalent (GAE) mg/100 g, a total flavonoid content of 54.09 ± 1.01 rutin equivalent (RE) mg/100 g, DPPH radical scavenging activity of 46%, and antioxidant activity of 213.25 ± 2.82 μM of Trolox equivalents (TEAC). C. sulcata extracts could prevent hydrogen peroxide (H₂O₂)-induced oxidative stress, reduce expression of the inflammatory markers nuclear Factor kappa B (NFκB) and phosphorylated IκBα (p-IκBα) in A549 human lung carcinoma cells, and inhibit Lipopolysaccharide (LPS)-induced THP-1 monocyte differentiation to an extent of 85%.     

Nonstarter lactic acid bacteria biofilms and calcium lactate crystals in Cheddar cheese

A sanitized cheese plant was swabbed for the presence of nonstarter lactic acid bacteria (NSLAB) biofilms. Swabs were analyzed to determine the sources and microorganisms responsible for contamination. In pilot plant experiments, cheese vats filled with standard cheese milk (lactose:protein = 1.47) and ultrafiltered cheese milk (lactose:protein = 1.23) were inoculated with Lactococcus lactis ssp. cremoris starter culture (8 log cfu/mL) with or without Lactobacillus curvatus or Pediococci acidilactici as adjunct cultures (2 log cfu/mL). Cheddar cheeses were aged at 7.2 or 10°C for 168 d. The raw milk silo, ultrafiltration unit, cheddaring belt, and cheese tower had NSLAB biofilms ranging from 2 to 4 log cfu/100 cm². The population of Lb. curvatus reached 8 log cfu/g, whereas P. acidilactici reached 7 log cfu/g of experimental Cheddar cheese in 14 d. Higher NSLAB counts were observed in the first 14 d of aging in cheese stored at 10°C compared with that stored at 7.2°C. However, microbial counts decreased more quickly in Cheddar cheeses aged at 10°C compared with 7.2°C after 28 d. In cheeses without specific adjunct cultures (Lb. curvatus or P. acidilactici), calcium lactate crystals were not observed within 168 d. However, crystals were observed after only 56 d in cheeses containing Lb. curvatus, which also had increased concentration of d(−)-lactic acid compared with control cheeses. Our research shows that low levels of contamination with certain NSLAB can result in calcium lactate crystals, regardless of lactose:protein ratio.     

Real-time polymerase chain reaction for the quantitative detection of tetA and tetB bacterial tetracycline resistance genes in food

A new, rapid, sensitive and specific method was developed to directly detect and quantify tetA and tetB in food. Both tet genes are two of the most frequently present tetracycline resistance genes in Gram-negative bacteria. A set of primers and Taqman probes was designed for each gene. The standard curves were performed using Escherichia coli BM13 (C600 RifR)/RP4 and E. coli NCTC 50365, which carry tetA and tetB, respectively. Meat and fish samples inoculated with these reference strains were used as a matrix to construct the standard curves for the analysis of 20 samples of chicken meat and 10 samples of hake (Merlucius merlucius). The limits of detection in pure culture were 5 cfu/mL (0.7 log cfu/mL) in the case of tetA, 50 cfu/mL (1.7 log cfu/mL) for tetB and 5 × 10² cfu/g (2.7 log cfu/g) for both genes in food samples. The results obtained by real-time quantitative polymerase chain reaction (qPCR) were compared to counts of tetracycline-resistant bacteria obtained by plating extracts of poultry and hake samples in culture media supplemented with 16 mg/L of tetracycline. Counts of tetracycline-resistant bacteria obtained by qPCR showed a positive correlation, especially interesting when compared with microbiological counts of tetracycline-resistant Enterobacteriaceae in poultry meat (r = 0.5509) and with tetracycline-resistant mesophilic aerobic bacteria in hake samples (r = 0.7146). The obtained results demonstrate that this method could be a useful tool for the direct quantification of the amount of bacterial strains that carry tetA and/or tetB genes in food samples.     

Resistances to benzalkonium chloride of bacteria dried with food elements on stainless steel surface

To confirm the importance of washing food sediments from the surface of food-related environments, we examined resistances against benzalkonium chloride of pathogenic bacterial (Escherichia coli O26, Pseudomonas aeruginosa and Staphylococcus aureus) cells dried and adhered on stainless steel dishes with milk, beef gravy or tuna gravy. Suspensions (0.1 ml) of these bacteria (8-9 log cfu/ml) were put on a 5 cm ? stainless steel dish and dried at room temperature (20-24 °C) for 90 min in a bio-clean bench with ventilation. Though these bacteria suspended with distilled water decreased 30-40 fold during the drying period, milk and the gravies protected the bacteria. Without the food elements, the adhered E. coli and Stap. aureus were decreased from 6 to<2 log cfu/dish by 0.5 mg/ml benzalkonium chloride (BKC) for 10 min treatment. Although Ps. aeruginosa showed resistance to BKC, the adhered cells were inactivated by 2.0 mg/ml BKC. However, the bactericidal effect disappeared by the food elements, particularly with milk, even at 1.0 and/or 2.0 mg/ml BKC levels. The protective efficiency of milk on bacteria disappeared if washed with water.     

Habituation to organic acid anions induces resistance to acid and bile in Listeria monocytogenes

We evaluated the intrinsic and inducible resistance of four human pathogenic strains of Listeria monocytogenes to acid and bile, factors associated with virulence. Cells were grown in media at pH 7.4, or in media at pH 6.0 containing 0 (HCl control) or 4.75 mM of different organic acids, harvested at stationary or mid log phase, and challenged for 1 h in acid or bile. Stationary phase cells were intrinsically more resistant to either challenge than log phase cells, and large differences between strains were evident among the latter. Compared to the HCl control, habituation to log phase with organic acids induced significant (p < 0.05) and meaningful (≥ 1 log) increases in acid resistance of three of four strains tested, and in bile resistance of two strains suggesting that exposure to organic acid anions may enhance virulence in L. monocytogenes.     

Identification of dairy farm management practices associated with the presence of psychrotolerant sporeformers in bulk tank milk

Some strains of sporeforming bacteria (e.g., Bacillus spp. and Paenibacillus spp.) can survive pasteurization and subsequently grow at refrigeration temperatures, causing pasteurized fluid milk spoilage. To identify farm management practices associated with different levels of sporeformers in raw milk, a bulk tank sample was obtained from and a management and herd health questionnaire was administered to 99 New York State dairy farms. Milk samples were spore pasteurized [80°C (176°F) for 12 min] and subsequently analyzed for most-probable number and for sporeformer counts on the initial day of spore pasteurization (SP), and after refrigerated storage (6°C) at 7, 14, and 21 d after SP. Management practices were analyzed for association with sporeformer counts and bulk tank somatic cell counts. Sixty-two farms had high sporeformer growth (≥3 log cfu/mL at any day after SP), with an average sporeformer count of 5.20 ± 1.41 mean log₁₀ cfu/mL at 21 d after SP. Thirty-seven farms had low sporeformer numbers (<3 log cfu/mL for all days after SP), with an average sporeformer count of 0.75 ± 0.94 mean log₁₀ cfu/mL at 21 d after SP. Farms with >25% of cows with dirty udders in the milking parlor were 3.15 times more likely to be in the high category than farms with ≤10% of milking cows with dirty udders. Farms with <200 cows were 3.61 times more likely to be in the high category than farms with ≥200 cows. Management practices significantly associated with increased bulk tank somatic cell count were a lack of use of the California mastitis test at freshening and >25% of cows with dirty udders observed in the milking parlor. Changes in management practices associated with cow cleanliness may directly ensure longer shelf life and higher quality of pasteurized fluid milk.     

Antibacterial effects of natural tenderizing enzymes on different strains of Escherichia coli O157:H7 and Listeria monocytogenes on beef

This study determined the efficacy of actinidin and papain on reducing Listeria monocytogenes and three mixed strains of Escherichia coli O157:H7 populations on beef. The average reduction of E. coli O157:H7 was greater than that of L. monocytogenes and higher concentrations of either protease yielded greater reduction in bacterial populations. For instance, actinidin at 700 mg/ml significantly (p ≤ 0.05) reduced the population of L. monocytogenes by 1.49 log cfu/ml meat rinse after 3 h at 25 & 35 °C, and by 1.45 log cfu/ml rinse after 24 h at 5 °C, while the same actinidin concentration significantly reduced the populations of three mixed strains of E. coli O157:H7 by 1.81 log cfu/ml rinse after 3 h at 25 & 35 °C, and 1.94 log cfu/ml rinse after 24 h at 5 °C. These findings suggest that, in addition to improving the sensory attributes of beef, proteolytic enzymes can enhance meat safety when stored at suitable temperatures.     

Antimicrobial activity of lactic acid bacteria against Listeria monocytogenes on frankfurters formulated with and without lactate/diacetate

Contamination by Listeria monocytogenes has been a constant public health threat for the ready-to-eat (RTE) meat industry due to the potential for high mortalities from listeriosis. Lactic acid bacteria (LAB) have shown protective action against various pathogenic bacteria. The aim of this study was to evaluate the antilisterial activity of a combination of three LAB strains (Lactiguard®) on L. monocytogenes. The combination of the LAB was inhibitory to L. monocytogenes inoculated onto frankfurters not containing lactate/diacetate after 8 weeks of refrigerated storage (0.6 log reduction compared to L. monocytogenes only control), and when a cell free extract (CFS) of the LAB was added with LAB even more inhibition was obtained (1.2 log reduction compared with L. monocytogenes only). In frankfurters containing lactate/diacetate the LAB and the LAB plus CFS were more effective in reducing growth of L. monocytogenes after 8 weeks of refrigerated storage (2 and 3.3 log reductions respectively).     

Antioxidative and anti-inflammatory activities of Citrus unshiu peel extracts using a combined process of subcritical water extraction and acid hydrolysis

Antioxidant and in vitro anti-inflammatory activities of citrus (Citrus unshiu) peel extracts and their acid hydrolysates were evaluated. Citrus peel extracts were extracted by subcritical water, hot water, and ethanol. Subcritical water extraction led to extract more phenolic compounds than hot water or ethanol extraction. Acid hydrolysis more than doubled the extracts’ total phenolics and flavonoids. Acid hydrolysates showed greater DPPH-radical scavenging activities and antioxidant activities, as assayed by β-carotene bleaching and ferric thiocyanate, than the initial extracts. Anti-inflammatory activities of citrus peel extracts and hydrolysates, determined by the inhibition of hyaluronidase activity, showed that the inhibition activities of hot water and ethanol extracts increased from 2.1 and 1.8% to 37.0 and 18.5%, respectively, upon acid hydrolysis; however, the anti-inflammatory activity of the subcritical water extract was not improved. These results indicated that acid hydrolysis of citrus peel extracts regardless of their extraction methods improved the antioxidative and anti-inflammatory activities.     

Development of a locally sustainable functional food based on mutandabota,a traditional food in southern Africa

A probiotic dairy product was developed on the basis of a traditional dish called mutandabota to enable resource-poor populations in southern Africa to benefit from a functional food. Mutandabota is widely consumed in rural southern Africa, making it an ideal food matrix to carry probiotics. First, a process to produce probiotic mutandabota was designed. Raw cow milk was boiled and subsequently cooled to ambient temperature (25°C). Next, dry pulp from the fruit of the baobab tree (Adansonia digitata L.) was added to the milk at a concentration of 4% (wt/vol). This mixture was inoculated with the probiotic Lactobacillus rhamnosus yoba and left to ferment for 24 h, while the growth of the bacterial culture was monitored. Final ingredients were then added to produce probiotic mutandabota that had 14% (wt/vol) baobab fruit pulp and 7% (wt/vol) sugar in cow milk. The pH of probiotic mutandabota was pH 3.5, which ensures that the product is microbiologically safe. The viable plate count of L. rhamnosus yoba increased from 5.8 ± 0.3 log cfu/mL at the point of inoculation to 8.8 ± 0.4 log cfu/mL at the moment of consumption, thereby meeting the criterion to have a viable count of the probiotic bacterium in excess of 6 log cfu/mL of a product. Baobab fruit pulp at 4% promoted growth of L. rhamnosus yoba with a maximal specific growth rate (μ_max) of 0.6 ± 0.2/h at 30°C. The developed technology, though specific for this particular product, has potential to be applied for the delivery of probiotics through a variety of indigenous foods in different regions of the world. Upon consumption, probiotic mutandabota is expected to improve the population's intestinal health, which is especially relevant for vulnerable target groups such as children and elderly people.