Effect of different extraction and precipitation methods on yield and quality of pectin

An experimental study has been conducted to determine the combined effects of different extraction conditions and precipitation method on the yield and quality of high methoxyl pectin from lemon peels. Pectin was extracted using different mineral acids (HCl, HNO₃ and H₂SO₄) at four concentration levels (0.025; 0.05; 0.1 and 0.2  m ), at 70 °C for 4 h. The soluble pectin was precipitated by iso-propanol or by an aluminium sulphate, Al₂(SO₄)₃, solution at pH 4. The extraction with HCl and HNO₃, at the highest concentrations investigated, followed by aluminium precipitation led to the best results in terms of yield (22–25%), quality and gelling power of pectin with a remarkable decrease of alcohol consumption as compared to the alcoholic precipitation under the same extracting conditions.     

Efficacy of Sulfuric Acid Scarification and Disinfectant Treatments in Eliminating Escherichia coli O157: H7 from Alfalfa Seeds Prior to Sprouting

ABSTRACT: E. coli O157:H7 reduction on inoculated alfalfa seeds was investigated using acid scarification treatments with or without subsequent application of sanitizers. Scarification with 0.1 to 2N H₂SO₄ for 2.5 to 45 min did not affect (p ≤ 0.05) seed viability. E. coli O157:H7 was reduced by 2.1 to 5.0 logs after treating with 0.1 to 2N H₂SO₄ for 5 to 20 min. Combined scarification (0.5N H₂SO₄) and H₂O₂ or CH₃COOH treatments enhanced microbial destruction by less than 1 log compared to sanitizer alone. Chlorine, Na₂CO₃, or Na₃PO₄ treatments preceded by scarification did not significantly increase microbial destruction compared to sanitizer alone. Appreciable reductions in seed germination were only observed with chlorine treatments.     

Desulfiting Dried Apricots by Hydrogen Peroxide

ABSTRACT: Removal of sulfites from excessively sulfited dried apricots using hydrogen peroxide (H₂O₂) was studied. Dried apricots were dipped into 0.5, 1.0, and 1.5% H₂O₂ solutions at 20 °C and 40 °C for various times. At 60 °C, apricots were also treated with 1% H₂O₂ solution. Removal of sulfites by H₂O₂ followed a 1st-order kinetic model. At 20 °C to 60 °C and 1% H₂O₂ concentration, the E_a value was 22.46 kJ mol⁻¹. H₂O₂ treatment caused lighter, more yellow, and less red dried apricots. Critical factors for H₂O₂ application are choosing the appropriate H₂O₂ concentration, temperature, and exposure time and without bleaching the natural color of dried apricots.     

AFLATOXIN LIKE FLUORESCENT SUBSTANCES IN SPICES

To minimize the risk of misidentifying some blue fluorescent substances inherent in spices as aflatoxin during analysis, several confirmatory chemical tests and developing solvent systems were evaluated. Chemical confirmation with 20% HCl, 20% H₂SO₄ and TFA and TLC development in chloroform + acetone (95:5 v/v) followed by anhydrous diethyl ether (multiple development) were useful to obviate the interfering fluorescent substances.     

Efficacy of two acidic sanitizers for microbial reduction on metal cans and low-density polyethylene film surfaces

ABSTRACT:  This study investigated 2 sanitizer formulations and compared them with hydrogen peroxide (H₂O₂). Formulation number 1 contained citric acid and sodium dodecylbenzene sulfonate (SDBS). Formulation number 2 contained SDBS, citric, lactic, phosphoric acids, and benzoic acid. Low concentration levels of the sanitizers (1.0% for formulation 1 and 0.5% for formulation 2) were compared with 35% H₂O₂ for their efficacies on Escherichia coli , Listeria innocua, and Saccharomyces cerevisiae inoculated onto low-density polyethylene (LDPE) films and metal cans at room temperature (23 ± 1 °C) and 40 °C. The results showed that both formulations 1 and 2 required >120 s to sanitize both materials from microbial populations at room temperature, while <15 s was needed for the H₂O₂. Except for formulation 1 on the E. coli inoculated LDPE film surface, the sanitizers completely eliminated the bacterial populations on both materials in 60 s at 40 °C. In general, the formulations were more effective for reduction of the microbial numbers on the can material when compared with the LDPE film. The E. coli showed greater tolerance for the sanitizers when exposed to the process conditions in this study. All sanitizers completely eliminated the test organisms in ≤36 s at 40 °C when tested on a commercial Benco Aseptic packaging machine.     

Comparison of six methylation methods for analysis of the fatty acid composition of albacore lipid

Six methods widely used to produce methyl esters for the gas chromatographic determination of the fatty acid composition of a marine lipid were compared. Four acid-catalyzed methods (1% H₂SO₄: CH₃OH; 5% HCl: CH₃OH; 7% and 14% BF₃: CH₃OH) and two base-catalyzed methods [0.5M NaOCH₃: CH₃OH; (1:4) tetramethylguanidine: CH₃OH] were used.
The use of BF₃: CH₃OH (7% and 14%) gave a lower content of 18:1 n9 than the other methods and produced an artefact (2.7–3.2% of total fatty acid content) eluting between the 20:5 and 24:1 fatty acid methyl esters. No significant differences were obtained between the other four methods.
Accordingly the use of BF₃: CH₃OH for transmethylation of marine lipids is not recommended. Results obtained in the other four methods showed that all are comparable.     

SPECIFICITY OF THE FERRIC-H2SO4 REAGENT FOR ALGINATES

SUMMARY— Alginate in foods was isolated from papain digests of the samples as the insoluble calcium salt. dispersed by sodium hexametaphosphate and a 1- to 5-ml aliquot of the dispersion 50–250 μg of sodium alginate) dried at 100°C. Heating of the anhydrous sample in the presence of the ferric-H₂SO₄ reagent for 12 min at 60°C produced a pink color with maximum absorption at 490–515 mμ and maximum density after aging for 90 min at 29±1°C. Under these conditions, proteins, amino acids (except tryptophane), other carbohydrates, vitamins. food additives and incipients did not interfere. The presence of water in the medium rendered the reaction nonspecific and increasing the temperature above 60°C or heating for longer periods at lower temperatures resulted in color formation by other polyuronides, especially pectin and pectic acid. Recoveries of alginate from several products were good: Milk, 94–98%; ice cream, 93.5–98%; pasteurized process cheese spread. 92.6-95%; chocolate milk, 92.4-95%; dietetic foods, 90-97.2%.     

Improved Sanitizing Treatments for Fresh Tomatoes

ABSTRACT:  Fresh tomatoes repeatedly have been associated with major outbreaks of salmonellosis; however, efforts to disinfect them with chlorine or other sanitizing agents have had only mixed success. Our objective was to determine whether hydrogen peroxide (H₂O₂) treatments would be more efficacious than conventional methods in disinfecting tomatoes containing human pathogens and, at the same time, be noninjurious to quality. Tomatoes were dip inoculated with Escherichia coli NRRL B-766 or a Salmonella cocktail and then held for 0, 24, or 48 h at 4 or 24 °C prior to treatment. Treatments included 200 ppm chlorine (Cl₂) at 20 °C for 3 min, water at 20 °C for 3 min or at 60 °C for 2 min, 1% H₂O₂ at 20 °C for 15 min or at 60 °C for 2 min, and 5% H₂O₂ at 60 °C for 2, 3, or 5 min. In tomatoes held 48 h postinoculation, the chlorine treatment was only marginally more effective than an equivalent water rinse in reducing the target bacterial population, while the hot water and 1% H₂O₂ treatments achieved reductions no greater than 1.3 logs. However, application of 5% H₂O₂ at 60 °C resulted in larger reductions. Efficacy of all treatments decreased as the time interval between inoculation and treatment increased. Greater reductions could not be achieved with 5% H₂O₂ at 60 °C by increasing the contact time or addition of surfactants, and these treatments caused some quality loss.     

Antimicrobial Treatments for Minimally Processed Cantaloupe Melon

ABSTRACT: Efficacy of decontamination treatments in reducing endogenous microbial populations on cantaloupe and in extending fresh-cut shelf-life were investigated. Composite rind plug samples were washed with water or solutions of sodium hypochlorite, H₂O₂, commercial detergent formulations containing dodecylbenzene sulfonic acid and phosphoric acid, or trisodium phosphate, and surviving microbial populations determined. Fresh-cut cubes were prepared aseptically from whole melons given similar treatments, and their visual appearance and bacterial population determined during storage at 4 °C. Population reductions on washed rind plugs were < 1 log with water, 1 to 2 logs with washing and sanitizing agents applied individually, and 3 logs with some sequential treatments with H₂O₂. H₂O₂ applied at 50 °C was superior to other whole-melon treatments, yielding a fresh-cut shelf-life of > 2 weeks.     

DETERMINATION OF CARBOXYMETHYLCELLULOSE IN FOOD PRODUCTS

SUMMARY –A method was developed to determine sodium carboxymethylcellulose (CMC) in food products containing three or more hydrocolloids after prior removal of interfering substances. Papain was used to digest the proteins; calcium chloride was added to precipitate algin and pectic acid and sulfated hydrocolloids were then precipitated by cetylpyridinium chloride (CPC) in the presence of 0.5M NaCl. Celite 535 or Hyflo Super Cel was added, the mixture filtered over Reeve angel No. 202 paper and the residue washed with 0.01% CPC-0.01M NaCl. The filtrate and washings were collected and diluted with distilled water to attain a final concentration of 0.2M NaCl at which concentration the CMC was precipitated selectively by CPC. The mixture was filtered over a Celite 535 or Hyflo Super Cel column and the residue washed with 0.5M Na₂SO₄ and then with 0.01% CPC-0.01M NaCl until the washings were negative to the phenol-H₂SO₄ reagent. Finally, the residue on the column was washed with hot 30% H₂SO₄ and the hydrolyzed CMC in the eluate determined by the 2,7-naphthalenediol test. Based on the amount added to mixtures, recoveries of 75–86% were obtained from milk and other highly complex and proteinaceous products, with a standard deviation of ± 0.58 mg, when 10 mg of CMC were added. The determination is critically dependent upon the degree of substitution (DS) of the CMC. As a consequence, the method cannot be applied with absolute certainty to unknown samples.     

Microbiological, physicochemical and organoleptic changes of shredded carrots stored under modified storage

The effect of initial head spaces of air, 4.9% CO₂/2.1% O₂/93% N₂ and 5% CO₂/95% N₂ on the microbial flora of shredded carrots was studied at 4 and 10°C. The microbial flora of shredded carrots comprised lactic acid bacteria, pseudomonads and yeasts. Lactic acid bacteria were the predominant organisms in all samples. The pH dropped during the storage of carrots and this was more pronounced at 10°C. The concentration of different organic acids such as lactic, acetic, tartaric, citric and succinic increased in all samples stored under modified atmosphere packaging conditions at both temperatures. The spoilage of carrots stored under 5% CO₂/95% N₂ was delayed, as indicated by the changes in their texture, colour and odour, compared with those samples stored under air or 4.9% CO₂/2.1% O₂/93% N₂.     

POTENTIAL FOR EXAGGERATION OF PCB CONTENTS OF PACKAGED FISH BY PHTHALATES FROM THE WRAPPING MATERIAL OR SOLVENTS

A convenient method for recovering PCBsfrom lipids is to digest the matrix in concentrated H₂SO₄ and recover the unaffected PCBs into hexane for determination by gas chromatography with electron capture detection. In a recent fish analysis case the peaks for these PCBs were accompanied by a large component identified as di- (2-ethylhexyl) phthalate, shown to have migrated into fish lipidfrom a heavy plastic wrap, and only partly destroyed by the H₂SO₄. The di-n-butyl and di-(2-ethylhexyl) phthalates bracket the major Aroclor peak region of chromatograms on a methyl silicone GC column and possibly a di-n-hexyl phthalate ester would very likely be superimposed directly on the PCBs. In the course of this work it was found that commercially available hexanes of presumed high quality contained the same di-(2-ethylhexyl) phthalate plasticizer in proportions high enough to be of concern in such analyses.     

Effects of Hot Rehydration in the Presence of Hydrogen Peroxide on Microbial Quality, Texture, Color, and Antioxidant Activity of Cold-stored Intermediate-moisture Sun-dried Figs

ABSTRACT: Pectin methylesterase (PME) causes considerable softening in intermediate-moisture (IM) figs rehydrated at 30°C and cold stored at 28% to 29% moisture content. Rehydration of figs at 80°C for 16 min inactivated PME partially (25–30%), but this did not prevent the softening over 3 mo of cold storage. Also, heating did not reduce the microbial load of figs significantly and increased their browning. In contrast, rehydration of figs 1st in 2.5% H₂O₂ at 80°C for 8 min and then in water at 80°C for 8 min reduced the microbial load of IM figs significantly, turned their brown color to yellow-light brown, and maintained their desired textural properties. The residual H₂O₂ in IM figs decomposed in 3 or 1.5 wk by the in situ catalase or by application of the iron (II) sulfate-ascorbic acid residue elimination method, respectively. Hot rehydration did not affect the antioxidant activity of IM figs, but treatment of figs with H₂O₂ increased their antioxidant activity slightly. These results indicate that the hot rehydration of figs in the presence of H₂O₂ and cold storage may be applied to obtain safe and SO₂-free light-colored IM fig products.     

Degradation Kinetics of Anthocyanins from Sour Cherry, Pomegranate, and Strawberry Juices by Hydrogen Peroxide

ABSTRACT: Degradations were studied at different hydrogen peroxide (H₂O₂) concentrations (9.31 to 27.92 mmol. L¹) over a range of 10° to 30 °C. Degradation of anthocyanins by H₂O₂ was described by first-order function. Comparison of t_1/2 values revealed that sour cherry anthocyanins were the most resistant to H₂O₂, followed by pomegranate and strawberry anthocyanins. Thus, the removal of residual H₂O₂ from the juice contact surfaces of aseptically packaged strawberry juices should be controlled more carefully to prevent anthocyanin degradation. Respective E_a values were between 9.4 to 11.1, 9.5 to 11.4, and 11.4 to 12.2 kcal.mol¹; and Q₁₀ values between 1.59 to 2.22, 1.62 to 2.05, and 1.76 to 2.36 for strawberry, sour cherry, and pomegranate anthocyanins.     

Shelf-Life Extension of Fresh Mushrooms (Agaricus bisporus) By Application of Hydrogen Peroxide and Browning Inhibitors

ABSTRACT: An experimental washing process for fresh mushrooms entailing immersion in 5% H₂O₂, followed by application of a sodium erythorbate-based browning inhibitor, was optimized, scaled up, and made continuous. The laboratory process described previously was modified by adding a pre-wash step using 0.5% to 1% H₂O₂, increasing the wash solution H₂O₂ concentration from 3% to 5%, and substituting 4% sodium erythorbate + 0.1% NaCl for the more complex browning inhibitor formulation used previously. A continuous, commercial-scale washing facility was built to test the new process. Mushrooms washed by this process were free of adhering soil, less subject to brown blotch than conventionally washed mushrooms, and at least as resistant to enzymatic browning as unwashed mushrooms during storage at 4 °C. Storage at 10 °C accelerated development of brown blotch and browning.     

Quantitative Determination of Carrageenan in Milk and Milk Products Using Papain and Cetyl Pyridinium Chloride

SUMMARY– Proteins in milk, chocolate milk, evaporated milk, and ice cream containing added carrageenan were digested with papain at 70°C in the presence of 1.0 M NaCl. The digest was adjusted to pH 8.0 to 8.5 with NaOH. Celite was added and the mixture filtered over glass wool. Carrageenan in the filtrate was precipitated with cetyl pyridinium chloride (C.P.C.) in the presence of 0.5 to 1.0 M KCl and Celite. The carrageenan-C.P. precipitate was washed with 0.1% C.P.C.-0.05 M KCI until the filtrate was negative to the Benedict's test. Then, it was dissolved in 30% H₂SO₄ and the carbohydrate content determined by the phenol-H₂SO₄ method.
At concentrations of 0.01 to 0.2% carrageenan, average recoveries of 92 to 102% were obtained from milk. For chocolate milk, evaporated milk and ice cream, and at a level of 0.1% carrageenan, recoveries of 90, 94 and 96%, respectively, were obtained. Optimum conditions for the isolation of the carrageenan cetyl pyridinium complex were established.     

Effect of some thermal and chemical pre-treatments on smoked oyster mushroom quality

The effect of different thermal and chemical pre-treatments on quality and enzyme activities of smoked mushroom was investigated. Mushrooms were blanched (water and steam) and dipped in different concentrations of SO₂, H₂O₂, ethylenediaminetetraacetic acid (EDTA) and citric acid for 10 min before smoking. Enzyme activities, colour characteristics, microbiological and sensory examinations were carried out every 2 weeks up to 8 weeks of storage at 4 °C. Smoked mushroom pre-treated with sulphites (SO₂), H₂O₂ and steam blanching had the best colour values, better scores for all sensory characteristics and lower non-enzymatic browning compared with the other pre-treatments. Pre-treatment against total aerobic bacteria, yeast and moulds was the most effective when using citric acid, EDTA and steam, followed by smoking of mushroom. The most effective pre-treatments on quality and safety of smoked mushrooms were those using H₂O₂ and steam. It can be concluded that thermal and chemical treatments followed by smoking of mushroom reduce enzyme activities and are suitable for preserving mushrooms.     

Factors Limiting the Efficacy of Hydrogen Peroxide Washes for Decontamination of Apples Containing Escherichia coli

Factors limiting efficacy of H₂O₂ washes and alternative decontamination strategies were investigated with Golden Delicious apples, inoculated with nonpathogenic Escherichia coli. Post-treatment rinsing decreased efficacy by eliminating residual H₂O₂. A 2-stage wash incorporating a rinse to remove surfactant residues prior to H₂O₂ application was developed. Rapid attachment of E. coli to apples prevented effective removal by washing with water. Surviving E. coli following a 5% H₂O₂ wash were concentrated in stem and calyx areas. Survival was independent of the time interval between inoculation and washing. E. coli inoculation of punctured apple surfaces resulted in growth at 20 °C and greater survival after washing with 5% H₂O₂. Improved decontamination methods are needed.     

Kinetics of Acid Hydrolysis of Defatted Peanut Flour

The kinetics of hydrolysis of defatted peanut flour as affected by treatment at 100, 110 and 120°C in 3N and 5N HCl were determined. Rates of hydrolysis of protein and destruction of reducing sugars were rapid at 120°C and in 5N HCl. About 90% of total amino acids were released after 4 hr. The overall rate of reaction followed second-order kinetics as monitored by the generation of free amino acids over time. This relationship was reliable for all acid and temperature treatment conditions when the extent of hydrolysis was less than 80%. The rate of hydrolysis of peanut protein was about 2.2 times faster for every 10°C increase. Hydrolysis in 3N HCl was about 2.3 times faster than in 3N HCl at the same temperature. The activation energy was =24 kcal mol^?1. The rate of liberation of individual amino acids with respect to temperature and HCl concentration, however, varied.     

Effect of hydrogen peroxide on quality of fresh-cut tomato

ABSTRACT:  The effect of hydrogen peroxide (H₂O₂; 0, 0.1, 0.2, and 0.4 M) on selected nutritional quality of fresh-cut tomato was investigated. Microbial population of tomato slices stored at 10 °C and treated with H₂O₂ was lower than the control by 1-(0.2 and 0.4 M) and 5-log (0.4 M), 3 and 7 d after processing, respectively. Dipping fresh-cut tomato into H₂O₂ resulted in reduced phenolic and antioxidant levels after 7 d in storage by at least 5% and 20%, respectively, and produced an initial decline in vitamin C and lycopene. Change in color values in the H₂O₂ treatments were associated with reduced carotenoid content. Our results confirmed antimicrobial benefits of H₂O₂ but revealed a compromise in antioxidant and carotenoid contents of fresh-cut tomatoes.