Log Cycles Research Articles

Modifying textural and functional characteristics of fish (Nemipterus japonicus) mince using high pressure technology.

Effect of high pressure in inducing textural and functional modification has been investigated in pink perch (Nemipterus japonicus) mince. Fish mince undergone pressurization at 200, 400 and 600MPa for a holding period of 10min and was compared against cooked mince (90°C; 40min). The treated mince at 400 and 600MPa lost its natural viscosity and behaved like cooked mince through denaturation and formation of protein aggregates. Textural characterisation showed the retention of tenderness in 200MPa treated samples, but become harder on application of higher pressures. Unlike heat gels, pressure induced gels were more smooth, white and elastic in nature. A decreased in reactive SH groups was observed in 400 and 600MPa treated samples due to the formation of disulfide bonds. Hydrophobic concentration was higher in cooked and 600MPa treatments whereas Ca2+-ATPase activity decreased after pressurization. On application of different pressures microbial reduction of 2-3 log cycles was achieved in the mince samples. Hence pressure treatments at lower ranges cannot alter the texture and functionality of protein and the mince can undergo processing as required. Besides extending shelf life, the treatments above 400MPa can make irreversible effect on texture quality and protein functionality which is similar to that of cooking.

Application of antimicrobial coating based on carboxymethyl cellulose and natamycin in active packaging of cheese

The effects of carboxymethyl cellulose (CMC)-natamycin (N; 0.05 and 0.5%) coating on the quality of high-moisture mozzarella cheese (HMMC) were examined. The cheeses were immersed in the coating solutions and then kept at 7 °C for 8 days and microbial specifications (i.e., total mesophilic count, total psychrophilic count, lactic acid bacteria, and yeast-mold), pH, weight loss, and sensory properties were examined. The results of the agar spot diffusion assay represented inhibitory effects of CMC-N coating solution on Aspergillus flavus, A. fumigatus, A. niger, Penicillium citrinum, and Candida albicans. In HMMC, the natamycin-free CMC coating caused a significant decrease (p < 0.05) in all microbial groups, while the addition of natamycin to the coating only reduced the count of mold and yeast. As a result, the coating with natamycin at 0.05 and 0.5% represented a 0.6 and 0.9 log cycle reduction in yeast-mold populations, respectively. Based on the total mesophilic count, the control samples reached the 7 log CFU/g on day 4, indicating a 4-day shelf life of HMMC, while in HMMC coated with and without natamycin this limit was achieved on the 8th day of storage, which indicates that the coatings have doubled the HMMC shelf life.

Essential oil in vapor phase in combination with Enterococcus mundtii STw38 to improve refrigerated hake fillets shelf-life

Essential oils (EOs) in vapor phase were applied together with the bacteriocinogenic strain E. mundtii STw38 to improve the shelf life of Argentinean hake -Merluccius hubbsi-. Evaluated EOs were oregano, thyme, rosemary, and lemongrass. In vitro results demonstrated their effectiveness against foodborne pathogen surrogate Listeria innocua, as well as against Lactobacillus plantarum, Shewanella putrefaciens, and fish indigenous biota. The most effective were oregano and lemongrass, showing the lowest minimal inhibitory concentration, and synergic activity when combined against L. innocua and S. putrefaciens. Furthermore, synergic mixtures promoted changes in target microorganisms cell wall. The composition of the volatile phase of a synergic EOs mixture showed a higher presence of oregano components. When applying the EOs alone in hake fillets, total bacteria count increased 3.3 log cycles whereas in the control system the increase was higher than 5 log cycles, and consumers evaluated similarly in taste and smell both the control and the EOs synergic mixtures. When adding the most concentrated synergic mixture (0.147 μL lemongrass/mL headspace and 0.195 μL oregano/mL headspace) together with the bioprotective culture, in 7 days total bacteria count only increased 3 log cycles, showing the effectiveness of the use of EOs together with E. mundtii STw38.

Quality and antioxidant activity of highbush blueberry fruit coated with starch-based and gelatine-based film enriched with cinnamon oil

In this study, the effect of starch-based and gelatine-based edible coating containing cinnamon oil on selected quality parameters and the metabolism of antioxidants in highbush blueberry fruit, in terms of extending their shelf life were investigated. Research showed that the application of cinnamon oil to edible coating positively influenced the quality of the fruit during storage. Coating with essential oil effectively inhibited the growth of yeast and mould in the fruit during storage. On the last day, the growth of yeast and mould in the fruit coated with cinnamon oil (10% COE) was 1.29 log cycles lower than in the control. Moreover, the essential oil reduced the loss of soluble solids but it did not significantly affect the acidity and weight loss of the fruit. Equally interesting was the effect of the coating with cinnamon oil on the antioxidant activity of the fruit. Blueberries coated with cinnamon oil were characterised by a lower ability to produce ROS, as well as a lower activity of antioxidant enzymes. On the final day, the level of ROS and the activity of SOD and CAT were lower than the control by 82%, 56% and 63% respectively. The level of polyphenols in the fruit coated with cinnamon oil was higher than in the control up to the 5th day of storage. However, the level of anthocyanins in this sample gradually decreased as the storage period extended. After 10 days, the loss of anthocyanins in the fruit with essential oil was around 37%.

APPLICATION OF BACTERIOCIN-PRODUCING LACTIC ACID BACTERIA ISOLATED FROM SALTED DRIED CAMEL MEAT (EL KADID) IN THE PRESERVATION OF GOAT CHEESE AGAINST Staphylococcus aureus

El kadid is a traditional North African food obtained by natural dehydration of One-humped camels (Camelus dromedarius) meat still produced through traditional method in Algeria. This traditional food matrix constitutes a rich ecological niche for the screening of bacteriocin-producing strains and lactic acid bacteria which contributes to the safety and preservation of foods. Fifteen lactic acid bacterial isolates from El kadid were tested for antibacterial activity and biopreservative effectiveness against Staphylococcus aureus. Only four strains exhibited bacteriocin activity against the two indicator bacteria, Listeria monocytogenes ATCC 4379G and Staphylococcus aureus ATCC 25923, in the neutralized cell-free supematant treated with catalase and proteolytic enzymes. Strain LB6, identified as Lactobacillus plantarum and characterized by the highest antimicrobial activity, was selected for further trials. Bacteriocin rate peaked during the stationary phase. The ideal temperature and pH for its formation were 37°C and 6.5, respectively. The bacteriocin was stable at high temperatures (30 min at 100°C) and active following incubation at pH levels ranging from 2 to 12. This strain showed high activity in fresh goat cheese (11–15 mm inhibition zone) having the ability to prevent the development of S. aureus, also reducing the inoculum level of pathogen by about 1 log cycle. These results revealed that this strain could be a promising biopreservative starter for the dairy industry. To the author ’s knowledge, this is the first report of L. plantarum being isolated in salted dried camel meat.

Effect of extraction conditions on the antioxidant compounds from habanero pepper ( Capsicum chinense ) and its potential use as antimicrobial

Habanero pepper is a good source of bioactive compounds with antioxidant capacity; however, up to now, some factors for increasing their extraction have not been investigated yet. This research aimed to evaluate the effect of solid-to-solvent ratio (1:250, 1:45, and 1:25 w/V), temperature (20, 35, and 50°C), and time (6, 15, and 24 hr) on the extraction of bioactive compounds and antioxidant capacity from habanero pepper following a Box–Behnken design. The optimal extract was evaluated in its capsaicinoids content by HPLC and as an antimicrobial against two foodborne pathogens. The response surface models adequately adjusted (R2 > .75) experimental data of bioactive compounds extraction from habanero pepper in the ranges of the variables proposed. Extract obtained under the optimal conditions (1:250 w/V, 50°C, and 24 hr) contains 1,617.9 mg/100 g and 628.0 mg/100 g of capsaicin and dihydrocapsaicin, respectively, showing a reduction of 1.23 ± 0.14 and 2.37 ± 0.10 log cycles for S. Typhimurium and S. aureus, respectively. Novelty impact statement Extraction of bioactive compounds from natural sources is currently on the rise. However, regardless the use of traditional or novel extraction technologies is necessary for the evaluation of factors that may affect the yield of bioactive compounds extraction. Habanero pepper is a well-known source of bioactive compounds with antimicrobial and antioxidant properties. However, until the moment, the effect of factors, such as temperature, time, solid-to-solvent ratio, etc., has been scarcely studied. Thus, this study may be a good starting point for future research on the extraction of bioactive compounds from the habanero pepper and find potential applications in food, biotechnological, pharmaceutical, among other industries.

Helicobacter pylori Is Present at Quantifiable Levels in Raw Vegetables in the Mediterranean Area of Spain

Vegetables are one of the main foodstuffs consumed in the Mediterranean diet. However, raw vegetables have been associated with relevant foodborne outbreaks worldwide. Accurate knowledge of the microbiological quantitative risks associated with these matrices is crucial in order to define effective control measures, avoiding the survival and dissemination of foodborne pathogens through the different food chain stages. The aim of the present study is the assessment of the prevalence of Helicobacter pylori (a unique carcinogenic biological agent recognized to date) on leafy vegetables (spinach, lettuce, and chard) by means of the detection of the specific pathogenicity vacA gene. A real-time quantitative polymerase chain reaction (qPCR) optimized approach was used to detect H. pylori-positive samples and the concentration of this pathogen (with a limit of detection equal to 10 cells). One hundred raw vegetable samples were acquired in markets corresponding to the Spanish Mediterranean area. Sliced vegetable leaves were homogenized and centrifuged, and DNA was extracted from the homogenates. qPCR results confirmed 20 out of 100 H. pylori-positive samples, with melting temperature (Tm) values in the range of 84.8–86.5 °C (TmvacA H. pylori = 85 °C). Amplicons were cut, purified, and sequenced to confirm the homology with the H. pylori vacA gene. A total of 17 out of 100 vegetable samples (12/45 (26.6%) lettuce, 2/21 (9.5%) spinach, and 3/34 (8.8%) chard samples) were finally confirmed as H. pylori-positive. Contamination levels were in the range of 1.5 ± 0.3 to 2.5 ± 0.1 log10 cycles (36–335 CFU/g leafy vegetables). Our results show that H. pylori is detected by qPCR at levels close to infectious doses in fresh vegetables, thus posing a food safety hazard.

Zero-Waste Approach Applied to Pomegranates for Prolonging Fish Burger Shelf Life.

In this study, the possibility of using whole pomegranate (juice, peel and seeds) according to the zero-waste approach, to prolong fresh fish shelf life, was evaluated. A preliminary antimicrobial in vitro test was carried out with peel and seeds as ground and re-ground powders. Then, the entire fruit, in the right proportions of juice and relative by-products as ground or re-ground powders, was added to fresh fish burger formulation to extend its shelf life. To this aim, a shelf-life test was performed on fortified fish products stored at 4 °C. Control samples were also tested for comparison. Specifically, the pH and microbiological and sensory quality of all the fish burgers were monitored during refrigerated storage for about 1 month. The results from the in vitro test clearly indicate that the peel is abundantly more effective than seeds on selected spoilage bacteria and that the ground peel powder is slightly more antimicrobial than the same re-ground powder. Results from the shelf-life test assessed that the control sample became unacceptable within a few days (about 3 days), while the samples with pomegranate juice and by-products maintained microbial stability for a longer time (2 or 3 weeks) (p < 0.05). The main microbiological problems are the proliferations of mesophilic and psychrotrophic bacteria, Pseudomonas spp. and Shewanella. The addition of pomegranate to the formulation allowed the fish spoilage to be controlled by at least 2 or 3 log cycles. In agreement with findings from the in vitro test, the best results from the microbiological point of view were found in fish burgers with juice, peel and seed ground powders. Furthermore, the addition of pomegranate was also appreciated from the sensorial point of view. In fact, products with pomegranate were prized for about 3 weeks for color, odor, appearance and texture of both raw and cooked products. Therefore, the current study reveals that the incorporation of the entire pomegranate, added in all parts according to the zero-waste concept, could promote a significant shelf-life extension of fish burgers, mainly due to the bioactive compounds present in fruit by-products, without changing the sensory quality.

Conventional and ohmic heating pasteurization of fresh and thawed sheep milk: Energy consumption and assessment of bacterial microbiota during refrigerated storage

This study aimed to assess the energy consumption of ohmic heating (OH) and conventional heating (CH) for pasteurization of fresh and thawed sheep milk and their impact on bacterial microbiota throughout refrigerated shelf-life (4 °C ± 1, 15 days). OH pasteurization using 8.33 and 5.83 V/cm electric field strength spent 72–73% less energy than CH pasteurization (515 KJ). The cultivation-dependent approach showed that at least 4.2 log cycle reductions were achieved in sheep milk submitted to CH and OH pasteurization, regardless sheep milk was fresh or thawed. Data from amplicon sequencing indicated that Staphylococcus was the most prevalent genus in raw samples at day 1 (F1D1: 58.35%; T1D1: 69.50%), while Pseudomonas became the most abundant after 15 days under cold storage (F1D15: 50.15% and T1D15: 54.50%). The relative abundance of all bacterial genera assessed remained similar on pasteurized samples by CH and OH throughout refrigerated storage. Industrial relevanceOhmic heating (OH) presents as a critical advantage rapid and uniform heating of fluid food material. No studies assessed the use of OH for pasteurization of sheep milk and to evaluate the impact of this technology on sheep milk bacterial microbiota during refrigerated storage. The findings of this study prove the feasibility of sheep milk pasteurization using OH8.33 V/cm. OH also ensured the bacteriological stability of sheep milk during 2 weeks of storage under refrigeration conditions prior to dairy products manufacturing. This approach comprises a cheaper and easier way to store milk when compared to frozen storage, with potential benefits to small farmers and dairy industries.

The effects of encapsulated probiotic bacteria on the physicochemical properties, staling, and viability of probiotic bacteria in gluten‐free bread

The aim of this study was to investigate the effect of microencapsulation with tragacanth gum and sago starch on the physicochemical properties, staling, and viability of probiotic bacteria in gluten-free sorghum bread. Lactobacillus acidophilus and Lactobacillus plantarum were used as probiotic bacteria and tragacanth gum and sago starch were used to the encapsulation of bacteria. Encapsulation increased water absorption (from 56% to 59%), dough development time, and farinograph number, and decreased the softening degree (from 27 to 17.2BU) and dough stability time. Encapsulation of probiotics also resulted in better moisture retention in bread during baking and storage, thereby reducing the intensity of staling. This process also increased the survival of probiotics during baking and storage by more than 2 log cycles. In summary microencapsulation of probiotics with tragacanth gum alone and in combination with sago starch could be an excellent way to improve the survival of probiotic bacteria and delay staling of bread. Novelty impact statement The effect of probiotic bacteria microencapsulation in sorghum bread using tragacanth gum and sago starch on physicochemical qualities, staling, and probiotic viability, was studied. Encapsulation of probiotics improved moisture retention in bread during baking and storage, thereby reducing the intensity of staling. Survival of probiotics during baking and storage was increased by more than two log cycles through this encapsulation.

Pulsed electric field for Escherichia coli inactivation in pumpkin juice and nectar

In this study experiments were performed using a batch pulsed electric field (PEF) system at different electric field strengths with a voltage of 35 kV and pulse frequency of 3 Hz, at 20 and 40°C, with pulse width between 0.8 and 1.0 µs, to evaluate the inactivation of Escherichia coli in pumpkin juice and nectar. The performance of the PEF technology can vary as a function of several process parameters and the conditions and procedures applied. The physicochemical characteristics (pH, total soluble solids, electrical conductivity) of the pumpkin juice were also evaluated. The juice showed 5.01 ± 0.01 of pH, 10.70 ± 0.11 (mS cm-1) of electric conductivity and 9.85 ± 0.07 of soluble solids while in nectar, these parameters were changed to 5.11 ± 0.01 of pH, 8.54 ± 0.21 of electric conductivity and 6.40 ± 0.12 of soluble solids. The use of a temperature of 40°C and pumpkin nectar (70:30, juice: distilled water) showed no difference in the bacterial reduction compared to 20°C and using 100% pumpkin juice, since in non-thermal processes it is better to use lower temperatures for less energy expenditure and less possibility of changes in raw material. The data showed that the PEF treatment reduced the microbial load moderately in all experiments, by a maximum of approximately 2.5 - 3 log cycles with 80 J g-1 of specific energy and above 26,000 V cm-1 of field strength

Inactivation of hepatitis A virus and norovirus on berries by broad-spectrum pulsed light

Foodborne diseases are still a major global health and economic burden, and are mainly caused by viral pathogens, such as human norovirus and hepatitis A virus, which may remain infective for long times on food contact surfaces and on produce. The strategies of viral inactivation applied in the industry are not generally suitable for delicate foods such as berries. Brief exposure to high-intensity white light (UV to IR) has been shown to inactivate many bacteria. The effectiveness of this treatment against foodborne viruses on fresh produce is largely unknown. We show that pulsed light treatment causes a moderate drop in the luminosity (L*, which ranges from bright (high) to dark (low)) of blueberries (to 36.31 ± 0.99 from 42.47 ± 1.17) and affects the luminosity of lettuce slightly but does not affect the appearance of strawberries, blackberries or raspberries. Hepatitis A virus and murine norovirus 1 are thus reduced by 2 log cycles. Viral inactivation on blackberries was less effective. These results will help food industries evaluate the suitability of pulsed light disinfecting technology for specific fruits and vegetables.

Effect of inulin and oat flour on viability of probiotics and physicochemical properties of reduced fat synbiotic ice cream

PurposeThe purpose of this study is to investigate the viability of probiotics, physicochemical and sensory properties of reduced fat synbiotic ice cream.Design/methodology/approachThe treatments were as follows: control was made by the addition of Lactobacillus salivarius NBIMCC 1589 and Lactobacillus crispatus NBIMCC 2451 (1:1). The treatments (T1, T2 and T3) were made with the addition of L. salivarius NBIMCC 1589 and L. crispatus NBIMCC 2451 (1:1) + 2% oat flour, 2% inulin and 4% oat flour + inulin (1:1). Physiochemical parameters (pH, moisture, fat, protein, fibre, ash, overrun, first dripping time and melting rate) were determined.FindingsThe ice cream with inulin and oat flour had lower moisture content, which was recorded 70.41, 69.88 and 68.82% for T1, T2 and T3, respectively. While the protein, fat and ash content of treated samples increased. The highest acidity (0.43%) was recorded in T3. The overrun increased by around 43% in T3 compared with control. The viable counts of probiotics were significantly (p = 0.05) decreased by two or three log cycles. Finally, T3 received the highest sensory score, which could be due to the combination between oat flour and inulin.Originality/valueA novel ice cream was produced using a combination of inulin and oat flour, which enhanced the viability of added probiotics. Reduced fat synbiotic ice cream was a good carrier for probiotics, which facilitates the production of healthy dairy products.

Tree species diversity of Pegunungan Bintang, Papua, Indonesia as potency of wood supply

Abstract. Murdjoko A, Djitmau DA, Sirami EV, Siburian RHS, Ungirwalu A, Mardiyadi Z, Wanma JF, Mofu WY, Marwa J, Susanti CME, Tokede MJ, Imburi CS, Sagrim M, Mamboai H, Sonbait LY, Dwiranti F, Salosa YY, Paembonan JB, Wiradyo ET, Unenor E, Benu NMH, Saragih ASB. 2021. Tree species diversity of Pegunungan Bintang, Papua, Indonesia as potency of wood supply. Biodiversitas 22: 5645-5655. The tropical rainforest is a primary global concern in many aspects. Therefore, this study aimed to describe the tree diversity in Pegunungan Bintang Forest, Papua, Indonesia. There are 10 dominant species from seedlings, saplings, poles, and trees, indicating the timber production potency. This study set systematic plots in Murkim and Teiraplu Sub-districts to collect taxonomic information, diameter, and clear bole height samples. The results showed that the forest was categorized as a tropical mixed due to diverse tree species. The leading plant families included Moraceae, Myrtaceae, Euphorbiaceae, Lauraceae, and Anacardiaceae, with various seedlings, saplings, poles, and trees. The potency of timber was reflected through sample distribution using the reverse J-shaped curve, identifying the merchantable trees with larger and smaller diameters as re-established. However, timber utilization management requires silvicultural treatments using selective logging by diameter limit and logging cycle for forest sustainability.

Effect of sub-lethal heat stress on viability of Lacticaseibacillus casei N in spray-dried powders

The potential of thermal adaptation enabling a probiotic Lacticaseibacillus casei N (N) to withstand heat stress and spray drying was investigated. Among the encapsulating agents used (maltodextrin, corn starch (CS), and acacia gum) for lactobacillus, CS had shown the highest survivability of 95.6% after spray drying. Further, the slurry prepared using L. casei (N), and CS as carrier material was subjected to sub-lethal heat stress at 45 and 50 °C for 60 min before spray drying. After spray drying, survivability was increased by 0.26 and 0.19 log in N + CS 45 and N + CS 50, respectively, compared to a control that was not treated to sub-lethal stress (N + CS). During storage studies for 90 days, the sub-lethal heat-stressed probiotic powders had shown better survivability at 4 °C. The survivability of L. casei (N) in spray-dried powders in simulated gastric fluid revealed that N + CS 45 had 3.06 log cycles higher survivability than N + CS. The SDS PAGE and FTIR analysis of intracellular proteins of heat-stressed L. casei (N) cells revealed overexpression of heat shock proteins indicating a change in protein structure. The study suggests that the sub-lethal heat stress before spray drying increases the viability of probiotic cultures, which have potential food applications.

Nitrogen Accumulation in Oyster (Crassostrea gigas) Slurry Exposed to Virucidal Cold Atmospheric Plasma Treatment

Viral contamination of edible bivalves is a major food safety issue. We studied the virucidal effect of a cold atmospheric plasma (CAP) source on two virologically different surrogate viruses [a double-stranded DNA virus (Equid alphaherpesvirus 1, EHV-1), and a single-stranded RNA virus (Bovine coronavirus, BCoV)] suspended in Dulbecco’s Modified Eagle’s Medium (DMEM). A 15 min exposure effectuated a statistically significant immediate reduction in intact BCoV viruses by 2.8 (ozone-dominated plasma, “low power”) or 2.3 log cycles (nitrate-dominated, “high power”) of the initial viral load. The immediate effect of CAP on EHV-1 was less pronounced, with “low power” CAP yielding a 1.4 and “high power” a 1.0 log reduction. We observed a decline in glucose contents in DMEM, which was most probably caused by a Maillard reaction with the amino acids in DMEM. With respect to the application of the virucidal CAP treatment in oyster production, we investigated whether salt water could be sanitized. CAP treatment entailed a significant decline in pH, below the limits acceptable for holding oysters. In oyster slurry (a surrogate for live oysters), CAP exposure resulted in an increase in total nitrogen, and, to a lower extent, in nitrate and nitrite; this was most probably caused by absorption of nitrate from the plasma gas cloud. We could not observe a change in colour, indicative for binding of NOx to haemocyanin, although this would be a reasonable assumption. Further studies are necessary to explore in which form this additional nitrogen is deposited in oyster flesh.

A new application for the valorisation of pomegranate seed oil: nanoencapsulation of pomegranate seed oil into electrospun nanomats for food preservation

SummaryPomegranate seed oil (PSO) contains many bioactive materials including antimicrobials, antioxidants, tocopherol and unsaturated fatty acids such as punicic acids. Utilising PSO with nanotechnological ways is a novel approach. Therefore, in this study, PSO‐loaded nanomats having an average diameter of 327 nm with 97.6% encapsulation efficiency were produced. Then, the protection potential of nanomats was determined in terms of the microbial and oxidative deterioration of food samples. On the 1st day of storage, the TMAB load of the control kashar cheese was 4.35 log CFU g−1, while it was 3.05 log CFU g−1 in the coated cheese (change: 1.3 logs). On the 20th day of storage, the TMAB load of the CK sample and PSc sample was 5.52 and 4.22 log CFU g−1, respectively (change: 1.3 logs). For fish fillets, nanoencapsulated PSO enabled a bacterial reduction of 1.22 log cycles after 9 days of storage. The total mould and yeast number of cheese samples increased during storage, but the increase was lower in the coated group. Nanomats also increased the oxidative stability of food samples. Thiobarbituric acid values of coated samples were lower than uncoated samples.

Effect of Sterilization on the Degree of Esterification, FTIR Analysis, and Antibacterial Activity of Durian-Rind Pectin

Pectin is a common food ingredient used as a rheology modifier and recently recognized as an emerging bioactive compound. Degree of esterification (DE) and molecular weight (MW) are important determinants of its bioactivity. This study evaluated the effect of moist heat sterilization (121 °C, 15 min) on pectin from Indonesian durian rind as an alternative method to modify pectin. Sterilized pectin was compared in terms of DE, Fourier transform infrared (FTIR) analysis, gel-forming ability, and antibacterial activity to non-sterilized pectin and standard citrus-peel pectin. Durian-rind pectin was identified as a low-methoxyl pectin with DE of 26.50% and weak antibacterial activity. After sterilization, the DE and pH decreased. It lost the ability to form a gel which indicated pectin was degraded to lower molecules. Loss of bands at 1760-1745 cm-1 indicated that pectin underwent ester hydrolysis and generated free carboxyl groups. On the other hand, the sterilized durian-rind pectin showed strong antibacterial activity towards Staphylococcus aureus and Escherichia coli, with a reduction of 5 log cycles and 3 log cycles, respectively (with the initial bacterial level of 5 log cfu/mL). These results indicated that depolymerization and deesterification of pectin by heat sterilization was able to improve the antibacterial activity of durian-rind pectin.

APPLICATION OF BACTERIOCIN-PRODUCING LACTIC ACID BACTERIA ISOLATED FROM SALTED DRIED CAMEL MEAT (EL KADID) IN THE PRESERVATION OF GOAT CHEESE AGAINST Staphylococcus aureus

El kadid is a traditional North African food obtained by natural dehydration of One-humped camels (Camelus dromedarius) meat still produced through traditional method in Algeria. This traditional food matrix constitutes a rich ecological niche for the screening of bacteriocin-producing strains and lactic acid bacteria which contributes to the safety and preservation of foods. Fifteen lactic acid bacterial isolates from El kadid were tested for antibacterial activity and biopreservative effectiveness against Staphylococcus aureus. Only four strains exhibited bacteriocin activity against the two indicator bacteria, Listeria monocytogenes ATCC 4379G and Staphylococcus aureus ATCC 25923, in the neutralized cell-free supematant treated with catalase and proteolytic enzymes. Strain LB6, identified as Lactobacillus plantarum and characterized by the highest antimicrobial activity, was selected for further trials. Bacteriocin rate peaked during the stationary phase. The ideal temperature and pH for its formation were 37°C and 6.5, respectively. The bacteriocin was stable at high temperatures (30 min at 100°C) and active following incubation at pH levels ranging from 2 to 12. This strain showed high activity in fresh goat cheese (11–15 mm inhibition zone) having the ability to prevent the development of S. aureus, also reducing the inoculum level of pathogen by about 1 log cycle. These results revealed that this strain could be a promising biopreservative starter for the dairy industry. To the author ’s knowledge, this is the first report of L. plantarum being isolated in salted dried camel meat.

Evaluation of the Membrane Damage Mechanism of Chlorogenic Acid against Yersinia enterocolitica and Enterobacter sakazakii and Its Application in the Preservation of Raw Pork and Skim Milk.

Plant-derived antimicrobial agents have adequate antimicrobial effects on food-borne pathogens, which can be used as food preservatives. The purpose of this study was to evaluate the antibacterial mechanism of chlorogenic acid (CA) against Yersinia enterocolitica and Enterobacter sakazakii. The minimum inhibitory concentration (MIC) of CA was determined by employing the broth microdilution method. Then, the cell function and morphological changes of Y. enterocolitica and E. sakazakii treated with CA were characterized. Finally, the growth inhibition models of Y. enterocolitica in raw pork and E. sakazakii in skim milk were constructed through the response surface methodology. The results demonstrated that CA has a satisfactory inhibitory effect against Y. enterocolitica and E. sakazakii with a MIC of 2.5 mg/mL. In addition, CA inhibited the growth of Y. enterocolitica and E. sakazakii via cell membrane damage, such as depolarization of the cell membrane, reduction in intracellular adenosine triphosphate (ATP) and pH levels, and destruction of cell morphology. Moreover, CA reduced two log cycles of Y. enterocolitica in raw pork and E. sakazakii in skim milk at a certain temperature. According to the corresponding findings, CA has the potential to be developed as an effective preservative to control Y. enterocolitica and E. sakazakii-associated foodborne diseases.