Acid In Food Products Research Articles

Determination of hydroxycarboxylic acids in food products by capillary electrophoresis

A procedure for the capillary-electrophoretic determination of lactic, malic, tartaric, and citric acids in food products was developed. The use of 3-nitrobenzoic acid as a light-absorbing component of the running buffer was proposed for the indirect photometric detection of these substances. This considerably increased the determination sensitivity (up to n × 10 μg/L), as compared with currently available analogs. The composition of the running buffer was optimized: 3-nitrobenzoic acid, 10 mM; cetyltrimethylammonium bromide, 0.5 mM; EDTA, 0.1 mM; and monoethanolamine, to pH 5.3. The procedure was tested with the samples of food products: fruits, juices, nectars, wines, beer, etc. The accuracy of the analytical results was confirmed by the standard addition method.

Kinetics of Bacillus coagulans spore inactivation in tomato juice by combined pressure–heat treatment

The efficacy of combined pressure–heat treatment was evaluated for the inactivation of Bacillus coagulans spores in tomato juice. A spore crop of B. coagulans 185A was prepared on nutrient agar plus 500mgL−1 dextrose and 3mgL−1 MnSO4·H2O, incubated at 50°C for 7d. Spores were suspended (1.7×108CFUmL−1) in tomato juice (pH 4.23) and treated at 600MPa and process temperatures of 75, 85, 95, 100 and 105°C, or 0.1MPa and process temperatures of 100 and 105°C for ≤15min. The inactivation data was fitted to estimate kinetic inactivation parameters using selected linear and non-linear models. The models were evaluated using the mean square error, regression coefficient and accuracy factor. Depending upon the process temperature, a combined pressure–heat treatment reduced the spore population by 1.5–3.4 logs during the 30s pressure come-up time. Pressure holding times of 10, 7, 4 and 3min and 40s were sufficient to inactivate the spores to below the detection limit (<10CFUmL−1) at 600MPa and 75, 85, 95, 100 and 105°C, respectively with no microbial growth during subsequent storage of samples at 37°C. In contrast, the application of heat alone needed holding times of 13 and 4min, at 100 and 105°C, respectively to inactivate the spores to undetectable level with no growth during storage. The D-values of spores inactivated by combined pressure–heat treatment ranged from 0.19 (600MPa, 105°C) to 2.10min (600MPa, 75°C), while they were 1.66 and 0.59min at 100 and 105°C, respectively under atmospheric conditions. Kinetic model analysis indicated relatively good fits of linear and Weibull models to the pressure–heat inactivation data at process temperatures of 75–95°C. The log-logistic model provided best fitting at process temperatures of 95–105°C. This study suggests that combined pressure–heat treatment may be used as a viable alternative to inactivate B. coagulans spores in acidic food products, like tomato juice.

Inactivation of Shiga toxin-producing Escherichia coli in single-strength lemon and lime juices containing preservatives.

The objective of this study was to determine the inactivation of non-O157 Shiga toxin-producing Escherichia coli (STEC) serotypes in comparison with O157 STEC in commercially produced, shelf-stable lemon and lime juices. The present validation tests confirmed that storage of the juices containing preservatives at room temperatures (22°C) for 3 days (72 h) ensures a >6-log reduction of O26, O45, O103, O111, O121, O145, and O157 STEC. These results demonstrate that non-O157 STEC had survival abilities comparable to those of E. coli O157:H7 strains in acidic food products such as lemon and lime juices (pH 2.5 ± 0.1); therefore, the storage conditions deemed to inactivate E. coli O157:H7 similarly inactivate the non-O157 serotypes.

An Optical Test Strip for the Detection of Benzoic Acid in Food

Fabrication of a test strip for detection of benzoic acid was successfully implemented by immobilizing tyrosinase, phenol and 3-methyl-2-benzothiazolinone hydrazone (MBTH) onto filter paper using polystyrene as polymeric support. The sensing scheme was based on the decreasing intensity of the maroon colour of the test strip when introduced into benzoic acid solution. The test strip was characterized using optical fiber reflectance and has maximum reflectance at 375 nm. It has shown a highly reproducible measurement of benzoic acid with a calculated RSD of 0.47% (n = 10). The detection was optimized at pH 7. A linear response of the biosensor was obtained in 100 to 700 ppm of benzoic acid with a detection limit (LOD) of 73.6 ppm. At 1:1 ratio of benzoic acid to interfering substances, the main interfering substance is boric acid. The kinetic analyses show that, the inhibition of benzoic is competitive inhibitor and the inhibition constant (Ki) is 52.9 ppm. The activity of immobilized tyrosinase, phenol, and MBTH in the test strip was fairly sustained during 20 days when stored at 3 °C. The developed test strip was used for detection of benzoic acid in food samples and was observed to have comparable results to the HPLC method, hence the developed test strip can be used as an alternative to HPLC in detecting benzoic acid in food products.

Simultaneous Determination of Benzoic Acid and Sorbic Acid in Food Products by CE after On-line Preconcentration by Dynamic pH Junction

An online dynamic pH junction method has been proposed for sensitive determination of benzoic acid (BA) and sorbic acid (SA) by capillary electrophoresis (CE). It was based on the decreased mobility of the analytes when they migrated from sample zone with low pH to background electrolytes with high pH. Under optimized conditions, the limits of detection (S/N = 3) of BA and SA were 0.03 and 0.02 mg L−1, respectively. According to the permitted limits of BA and SA in food (GB2760), the samples can be diluted about 2,000–20,000-folds to estimate whether the contents of BA and SA are in the safety range. Beverage, vinegar and fruit jam samples were analyzed after simple dilution, and the results were satisfactory with the recoveries in the range of 91–108%. The whole analysis process needs about only 10 min, which is much faster than the method of liquid–liquid extraction followed by CE determination.

What Went In When Trans Went Out?

Despite the obvious theoretical health benefits of replacing trans fatty acids with other fatty acids in food products, concern has been expressed that this change might increase the intake of saturated fatty acids. The authors examined which types of fatty acids are present in various popular foods as compared with similar foods that contain low concentrations of trans fatty acids.

The possibility of increasing at the conjugated linoleic acid content in pork

The composition of fatty acids in food products is a significant factor in human health. Feeding can significantly influence the composition of fatty acids in the animal fat. We analysed the effect of feeding high CLA-content (conjugated linoleic acid) feed on the composition of fatty acids in pork. The animals were grouped according to the following: Group 1) feeding experimental, ghee-mixed feed for 76 days, Group 2) feeding the same feed, but only for 33 days, Group 3) feeding sunflower-oil-mixed feed for 76 days. Ghee contains CLA in high amount. The aim of our experiment is to analyse how the high CLA content influences the fatty acid content of pork. In the end of the fattening experiment the animals were slaughtered, then samples were taken from the loin, ham, abdomen and backfat from 10 animals from each group and analysed the fatty acid content. We found significant differences between the average fatty acid content of the samples. As an effect of feeding ghee-enriched feed, the CLA content significantly increased, compared to the control group. However, the linoleic acid and the arachidonic acid content were lower, and the proportion of fatty acids was also lower when feeding control feed.

Isolation, identification and typification of Alicyclobacillus acidoterrestris and Alicyclobacillus acidocaldarius strains from orchard soil and the fruit processing environment in South Africa

Alicyclobacillus acidoterrestris and Alicyclobacillus acidocaldarius are thermo-acidophilic, non-pathogenic, spore-forming bacteria that can survive the typical heat processing of fruit juices and concentrates. Bacterial endospores then germinate, grow and cause spoilage of acid food products. Species of Alicyclobacillus were isolated from orchard soil and a fruit concentrate production factory in South Africa. Preliminary identification of the isolates was based on morphological, biochemical and physiological properties. Identification at species level was done by PCR amplification using genus-specific primers and 16S ribosomal RNA (rRNA) gene sequencing. The majority of isolates belonged to the species A. acidoterrestris, but A. acidocaldarius was also isolated and identified. As far as we could determine, this is the first report of the isolation of A. acidoterrestris from wash water and soil outside a fruit processing plant, as well as the isolation of A. acidocaldarius from vinigar flies. The genotypic relatedness between strains of A. acidoterrestris and between strains of A. acidocaldarius was determined by RAPD-PCR. Sixteen isolates identified as A. acidoterrestris grouped into four clusters based on RAPD-PCR banding patterns, suggesting that they belong to at least four genotypic groups. Three isolateT:/PGN/ELSEVIER/YFMIC/web/00001155/s identified as A. acidocaldarius gave three unique banding patterns.

Determination of benzoic acid and sorbic acid in food products using electrokinetic flow analysis–ion pair solid phase extraction–capillary zone electrophoresis

An electrokinetic flow analysis system (EFA), consisting of one electroosmotic pump, five solenoid valves and one on-line homemade solid phase extraction (SPE) unit, combined with capillary zone electrophoresis (CZE) was proposed to determine benzoic acid and sorbic acid in food products. Tetrabutylammonium bromide (TBAB) was adopted as an ion pair reagent to improve the retention of the preservatives on C 8-bonded silica sorbent, which was also used to remove sample matrices. By using the SPE unit, the EFA–SPE–CZE system was able to perform the SPE operation and CZE separation simultaneously. With a modified interface of EFA and CZE, the buffer consumption was reduced to 130 μL for each running. The preservatives were separated and determined under optimized conditions with p-hydroxybenzoic acid as an internal standard. The relative standard deviation (R.S.D.) of peak area for each analyte was less than 3.1% ( n = 5) and the limits of detection (LODs) ranged from 10 to 20 ng mL −1 ( K = 3, n = 11).

WHEY POWDER AS A CARRIER IN SPRAY DRYING OF SUMAC CONCENTRATE

ABSTRACT Whey and milk powders and guar gum were tested for their use in spray drying of the sumac flavor. Freshly harvested sumac berries were used to prepare the sumac extract for the spray drying. The ratio of carrier to core material (the sumac flavor) was fixed as 4:1 g/g for all samples and the soluble solids content in the solution was adjusted to 5, 10, 15, 20 and 25%. Absorbance (510 nm), acidity and pH were measured in the solution and SDP. The percent retention of flavoring compounds was determined. When milk powder was added to the sumac solution, it coagulated because of the acidity of sumac solution; therefore, it was not a suitable carrier for sumac. Another carrier was guar gum. However, it was not fed into the spray dryer because of its high water‐holding capacity, which caused a viscous solution. Whey powder was the more suitable carrier to entrap sumac flavor. In addition, the taste of the final SDP was acceptable in which it can be added to slightly acidic food products (pH value of 5.2–5.7). It was also observed that the increasing initial solids content from 5 to 25% increased the retention of flavoring compounds from 6 to 11% based on the absorbance. In addition, the retention based on acidity was increased from approximately 14 to 70%, when the initial solids content increased from 5 to 25%. PRACTICAL APPLICATIONSThis study showed that whey powder can be used for encapsulation of sumac flavor using spray drying. Development of spray‐dried flavoring compounds is very useful to the food industry. Eventually, the new product may be used in different formulations as an additive instead of the sumac extract. Additionally, this carrier may be used for other natural acidic fruit extracts in encapsulation operations.

Dietary levels of trans-fatty acids: basis for health concerns and industry efforts to limit use

Dietary trans-fatty acids at sufficiently high levels have been found to increase low-density lipoprotein cholesterol and decrease high-density lipoprotein cholesterol compared with diets high in cis monounsaturated or polyunsaturated fatty acids. The dietary levels of trans-fatty acids necessary to do this appear to be approximately 4% of energy or higher to increase low-density lipoprotein cholesterol and approximately 5% to 6% of energy or higher to decrease high-density lipoprotein cholesterol, compared with control diets essentially trans-free. In response, the food industry is working on ways to eliminate or greatly reduce trans-fatty acids in food products. Current efforts focus on 4 technological options: (1) modification of the hydrogenation process, (2) use of interesterification, (3) use of fractions high in solids from natural oils, and (4) use of trait-enhanced oils. Challenges to the food industry in replacing trans-fatty acids in foods are to develop formulation options that provide equivalent functionality, are economically feasible, do not greatly increase saturated fatty acid content, and meet the regulatory deadline of January 1, 2006.

A PCR Assay for Detection of Acetic Acid–Tolerant Lactic Acid Bacteria in Acidic Food Products

A PCR assay for the detection of acetic acid–tolerant lactic acid bacteria in the genera of Lactobacillus and Pediococcus was developed in this study. Primers targeting the bacterial 16S rRNA gene were newly designed and used in this PCR assay. To determine the specificity of the assay, 56 different bacterial strains (of 33 genera), 2 fungi, 3 animals, and 4 plants were tested. Results were positive for most tested bacterial members of 16S rRNA gene–based phylogenetic groups (classi ed in the Lactobacillus casei and Pediococcus group), including Lactobacillus fructivorans, Lactobacillus brevis, Lactobacillus buchneri, Lactobacillus plantarum, and Lactobacillus paracasei. For all other bacterial strains and eukaryote tested, results were negative. Bacterial DNA for PCR was prepared with a simple procedure with the use of Chelex 100 resin from culture after growth in deMan Rogosa Sharpe broth (pH 6.0). To test this PCR assay for the monitoring of the acetic acid–tolerant lactic acid bacteria, L. fructivorans was inoculated into several acidic food as an indicator. Before the PCR, the inoculation of 10 to 50 CFU of bacteria per g of food was followed by a 28-h enrichment culture step, and the PCR assay allowed the detection of bacterial cells. Including the enrichment culture step, the entire PCR detection process can be completed within 30 h.

Injury recovery of foodborne pathogens in high hydrostatic pressure treated milk during storage

Bacteria are expected to be injured or killed by high hydrostatic pressure (HHP). This depends on pressure levels, species and strain of the microorganism and subsequent storage. Injured bacteria may be repaired which could affect the microbiological quality of foodstuffs with an important safety consideration especially in low acid food products. In this study two Gram-positive ( Listeria monocytogenes CA and Staphylococcus aureus 485) and two Gram-negative ( Escherichia coli O157:H7 933 and Salmonella enteritidis FDA) relatively pressure resistant strains of foodborne pathogens were pressurized at 350, 450 and 550 MPa in milk (pH 6.65) and stored at 4, 22 and 30°C. The results of shelf life studies indicated two types of injury, I1 and I2, for all the pathogens studied. It is obvious that I2 type injury is a major injury and after its repair (I2 to I1), the cells can form colonies on non-selective but not on selective agar. The formation of colonies on both selective and non-selective agar occurs only after full recovery of injury (I1 to AC). The results presented in this study show that even if injured cells are not detected immediately after HHP treatment, I2 type injury could be potentially present in the food system. Therefore, it is imperative that shelf life studies must be conducted over a period of time for potential repair of I2 type injury either to detectable injury (I1) or to active cells (AC) to ascertain microbiological safety of low acid food products.

Using capillary isotachophoresis for the determination of biogenic amines and D-isocitric acid in food products.

This paper presents results achieved in the determination of biogenic amines in various food products and quality evaluation of some commercial orange juices by capillary isotachophoresis. The highest amount of histamine was determined in frankfurters (146.75 mg x kg(-1)); the content of tyramine was either under detection limit of method or it was present in very low concentrations. The highest amount of cadaverine was determined in Karicka cheese (666.36 mg x kg(-1)). The limit of determination was 1.59 mg x kg(-1) for histamine and 1.25 mg x kg(-1) for tyramine. The recovery of method ranged from 95.4 to 104.9%. Surprisingly it was found that many organge juice samples did not reach required values according to the Code of Practice. The lowest ratio of citric to D-isocitric acids was found in Happy day juice (44.1). Limit of determination was 1.62 mg x dm(-3) for citric acid and 2.00 mg x dm(-3) for D-isocitric acid. The recovery of the method ranged from 89 to 96.5%.

Direct chiral resolution of tartaric acid in food products by ligand exchange capillary electrophoresis using copper(II)– d-quinic acid as a chiral selector

Chiral resolution of native dl-tartaric acid was performed by ligand-exchange capillary electrophoresis using copper(II)– d-quinic acid as a chiral selector. Factors affecting chiral resolution, migration time, and peak area of tartaric acid were studied. The running conditions for optimum separation of tartaric acid were found to be 1 m M copper(II) sulfate–10 m M d-quinic acid (pH 5.0) with an effective voltage of −15 kV at 30°C, using direct detection at 250 nm, and resolution of racemic tartaric acid was approximately 1.3. With this system, chiral resolution of dl-tartaric acid in food products was conducted successfully.

Direct chiral resolution of lactic acid in food products by capillary electrophoresis

Chiral resolution of native dl-lactic acid was performed by capillary electrophoresis using 2-hydroxypropyl-β-cyclodextrin as a chiral selector. Various factors affecting chiral resolution, migration time, and peak area of lactic acid were studied. The running conditions for optimum separation of lactic acid were found to be 90 m M phosphate buffer (pH 6.0) containing 240 m M 2-hydroxypropyl-β-cyclodextrin with an effective voltage of −30 kV at 16°C, using direct detection at 200 nm. In order to enhance the sensitivity, sample injection was done under a pressure of 50 mbar for 200 s. On-line sample concentration was accomplished by sample stacking. With this system, d- and l-lactic acids in food products were analyzed successfully.

DEGRADATION OF ASCORBIC ACID IN DRYING PROCESS -A COMPARISON OF DESCRIPTION METHODS

ABSTRACT The degradation kinetics of ascorbic acid in food products is presented in the paper. Vibrofluidized method of drying was considered. Experiments were carried out for a model substance (silica gel)and agricultural products, namely: fresh green peas, potatoes and cabbage. Experimental data were described by means of three mathematical methods: a multilayer perceptron (MLP) model, a mathematical model of degradation kinetics of ascorbic acid and a hybrid model. The hybrid model connects neural computation with the mathematical model. All approaches provide an excellent process description. In the case of multilayer perceptron, the proposed method is simpler to implement when compared to the mathematical and the hybrid methods.

Thermal resistance ofAlicyclobacillus acidoterrestrisspores in different buffers and pH

The influence of buffers and pH on the thermal resistance of a novel flat sour-type of spoilage bacterium,Alicyclobacillus acidoterrestris, was investigated. At a low concentration (20 mM), decimal reduction times (D-values) in citrate and phosphate buffers were 13.6 and 12.9 min, respectively, showing little variation. At a high concentration (100 mM), however, theD-value in citrate buffer, 14.4 min, was significantly higher than that in the phosphate buffer, 12.3 min.D-values in McIlvaine buffers did not vary widely within the pH range of 3.0 to 8.0. At 88, 90, 92 and 95°C in McIlvaine buffers,D-values were 24.1–29.1, 14.8–16.8, 5.7–7.1 and 2.2–2.8 min, respectively. The thermal resistance ofA. acidoterrestrisspores was affected very little by varying the pH of the heating menstruum. TheZ-values also did not vary widely as the pH varied among the different buffers, ranging from 6.4 to 7.1°C. It was evident thatA. acidoterrestrisspores showed a special relationship, unknown among other bacterial spores, between their thermal resistance and the pH of the heating menstruum. Therefore,A. acidoterrestrisshould be targeted when the quality of acidic food products is being tested.

Increased Detection of Acid-Injured Escherichia coli O157:H7 in Autoclaved Apple Cider by Using Nonselective Repair on Trypticase Soy Agar

Three different acid-resistant strains of Escherichia coli O157:H7 were inoculated individually and as a cocktail into sterile apple cider (pH 3.2) at a level of approximately 105 cells per ml and incubated at 2°C. Samples were plated on Trypticase soy agar (TSA), violet red bile agar (VRBA), sorbitol MacConkey agar (SMA), and Petrifilm E. coli count plates (Petrifilm) at 24-h intervals. Repair of acid-injured cells was assessed by surface plating cider samples on TSA and allowing a 2-h room-temperature incubation period followed by overlaying with double-strength VRBA or SMA. Since SMA is a surface plate medium, the repair procedure was modified by overlaying SMA with Trypticase soy broth after 2 h of room-temperature incubation. Populations of all three strains and the cocktail of strains decreased rapidly in apple cider and approached undetectable levels within 72 h. At 24 and 48 h, 98.4% and >99% of the E. coli populations were injured, respectively. Repair procedures significantly (α = 0.05) increased detection of E. coli O157:H7. After 72 h E. coli O157:H7 was not detected by using SMA and Petrifilm; however, it was detected using repair procedures. Although detection levels were increased with resuscitation procedures, the levels detected were still lower than those obtained using nonselective TSA. This research confirms the need for special recovery steps when analyzing acidic food products suspected of containing E. coli O157:H7.

Recent case histories of food product-metal container interactions using scanning electron microscopy-x-ray microanalysis.

Scanning electron microscopy (SEM) and x-ray microanalysis (EDS) were used to investigate stress corrosion cracking (SCC) in plain tinplate food cans, product discoloration, filiform corrosion, pitting/perforation corrosion, and loss of coating adhesion in enameled food cans. Intergranular SCC of uncoated tinplate occurred in canned pineapple juice. This is a rare occurrence in acid food products. The fracture developed in the can headspace only at the product line/metal interface by an interaction of the detinned metal surface with stress-inducing compounds in the product. Black discoloration of rice granules in the can headspace of a chicken and rice product was caused by the formation of metal sulfides. The source of the metal contamination was traced to metallic dirt in the coating on the tin-free-steel end. Blackening of light tan-colored olives and brine occurred after 1 year of storage in enameled tinplate containers as a result of pitting corrosion at the side seam weld. The cause of the pitting was a defective side seam stripe which failed to protect the weld. A perforation problem occurred at the score line of aluminum-tinplate bimetallic cans. The failure was caused by the high chloride content of the fruit product. Filiform corrosion resulted in perforations that occurred on the outside surfaces of two-piece tin-free steel cans packed with tuna. The cause of the corrosion was related to scratch defects in the exterior coating and the presence of chloride and sulfate cannery residues in the corroded areas. An enamel adhesion failure developed inside two-piece tin-free steel cans that contained mushrooms. Wrinkles in the coating which were introduced during can manufacture were cracked. The fractures were pathways for product-steel interaction which resulted in container failure.