Cassava starch as a stabilizer of soy-based beverages

Soy-based beverages are presented as healthy food alternatives for human nutrition. Cassava (Manihot esculenta, Crantz) starch is relatively inexpensive, widely available in Brazil and is broadly used by the food industry due to its desired properties that result from pasting. The objective of this study was to develop soy-based beverages with good sensory quality using native cassava starch as a stabilizer and maintaining the nutritional value that makes this product a functional food. The developed formulations featured a range of cassava starch and soybean extract concentrations, which were tested in a 2² experimental design with three central points. The results of sensory analysis showed that the studied variables (cassava starch and soybean extract concentrations) did not have a significant effect with respect to a 5% probability level. When considering the apparent viscosity, on the other hand, the variables had a significant effect: the increase in soybean extract and cassava starch concentrations caused an increase in the viscosity of the final product. The profile of isoflavones in the tested formulations was similar to the profiles reported in other papers, with a predominance of the conjugated glycosides over the aglycone forms.

Antimicrobial activity of Chinese bayberry extract for the preservation of surimi

BACKGROUND

Chemical preservatives such as sodium nitrite and potassium sorbate have been widely used to keep surimi products fresh. However, the potential harmfulness to human health cannot be ignored. This study was conducted to develop natural preservatives for the storage of Collichthys surimi.

RESULTS

Among the eight Chinese traditional herbs and fruits, Chinese bayberry extract showed the greatest inhibitory effect against surimi spoilage bacteria Serratia marcescens and Pseudomonas aeruginosa. Moreover, N-butanol phase extract of bayberry (NB) showed the greatest activity among the different phases of bayberry extract. When Chinese bayberry extract was combined with tea polyphenol, an additive inhibitory effect was observed on growth of Hansenula anomala, Micrococcus luteus, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. Our results further indicated that the shelf life of surimi products stored at room temperature can be extended when supplemented with Chinese bayberry extract.

CONCLUSION

Our results suggest that Chinese bayberry extract can be used as a natural preservative for the storage of Collichthys surimi.

Concentration of antioxidant polyphenols from Thymus capitatus extracts by membrane process technology

Thymus capitatus is a Mediterranean plant characterized by its antioxidant polyphenols of which the most known are the carnosic and rosmarinic acids. In this way, this study aims to concentrate these acids by membrane processes. The thyme essential oil composition was established by capillary GC-MS and 27 components were identified representing 98.93%± 1.97% of total oils. The antioxidant test for permeate and retentate of methanolic and aqueous extract were determined using 3 types of membranes. The results showed that the synthetic NF membrane is able to trap and concentrate phenolic compounds in the retentate much better than the NF commercial and UF synthetic membrane. The results of the total phenolic content (TPC) showed a significant value of the polyphenol content present in the aqueous extract with 175.53 mg Gallic Acid Equivalents (GAE)/g of extract. The spectrum of the aqueous extract of Thymus capitatus showed the presence of 3 visible peaks, the 1st one at 217 nm corresponding to the carnosic acid, the 2nd one at 277 nm for essential oils, and the last one at 326 nm attributed to the rosmarinic acid. The commercial membrane NF-DK succeeded to concentrate rosmarinic acid and can be considered as a stage towards the concentration of this product with a high added value.

Chemical composition and antimicrobial activity of the essential oil of kumquat (Fortunella crassifolia Swingle) peel

The aim of this study was to determine the main constituents of the essential oil isolated from Fortunella crassifolia Swingle peel by hydro-distillation, and to test the efficacy of the essential oil on antimicrobial activity. Twenty-five components, representing 92.36% of the total oil, were identified by GC-MS analysis. The essential oil showed potent antimicrobial activity against both Gram-negative (E. coli and S. typhimurium) and Gram-positive (S. aureus, B. cereus, B. subtilis, L. bulgaricus, and B. laterosporus) bacteria, together with a remarkable antifungal activity against C. albicans. In a food model of beef extract, the essential oil was observed to possess an effective capacity to control the total counts of viable bacteria. Furthermore, the essential oil showed strongly detrimental effects on the growth and morphological structure of the tested bacteria. It was suggested that the essential oil from Fortunella crassifolia Swingle peel might be used as a natural food preservative against bacteria or fungus in the food industry.

Encapsulation of thyme (Thymus serpyllum L.) aqueous extract in calcium alginate beads

BACKGROUND

Encapsulation of Thymus serpyllum L. aqueous extract within calcium alginate beads was studied in order to produce dosage formulations containing polyphenolic compounds. Electrostatic extrusion was applied for encapsulation of thyme aqueous extract in alginate gel beads. In addition to hydrogel beads, heat-dried and freeze-dried forms of beads were examined.

METHODS

Encapsulation systems were examined and compared in order to choose the optimal one with respect to entrapment efficiency, preservation of antioxidant activity and thermal behaviour under heating conditions simulating the usual food processing.

RESULTS

The beads obtained with approximately 2 mg g⁻¹ of gallic acid equivalents encapsulated in 0.015 g mL⁻¹ of alginate were spheres of a uniform size of about 730 µm. Encapsulation efficiency varied in the range 50-80% depending on the encapsulation method. Besides, the analysis reveals that the encapsulation process and the material used did not degrade the bioactive compounds, as the total antioxidant content remained unchanged. This was verified by Fourier transform infrared analysis, which proved the absence of chemical interactions between extracted compounds and alginate. Addition of a filler substance, such as sucrose and inulin, in the dried product reduced its collapse and roundness distortion during drying process.

CONCLUSION

This study demonstrates the potential of using hydrogel material for encapsulation of plant poplyphenols to improve their functionality and stability in food products.

Polar compounds isolated from the leaves of Albertisia delagoensis (Menispermaceae)

Aqueous infusions of the leaves of the shrub Albertisia delagoensis (Menispermaceae) are used in South Africa in traditional Zulu medicine to alleviate a variety of symptoms, including fever, and intestinal problems. We report the analysis of such an aqueous extract using the HPLC-NMR technique. A number of polar compounds were identified, including proto-quercitol, nicotinic acid, allantoic acid, 3,4-dihydroxy-benzoic acid, phthalic acid and the aporphine alkaloid derivative roemrefidine. Allantoic acid and roemrefidine have been fully characterised by (1)H- and (13)C-NMR and mass spectrometry. Earlier reports of antiplasmodial activity of roemrefidine and of A. delagoensis extracts are correlated with this study and with the antipyretic properties of neutral aqueous extracts.

Chemical composition and antimicrobial activity of essential oils of Thymus algeriensis, Eucalyptus globulus and Rosmarinus officinalis from Morocco

BACKGROUND

The present study reports on the antimicrobial activity and chemical composition of the essential oils (EOs) of Thymus algeriensis, Eucalyptus globulus and Rosmarinus officinalis from Morocco.

RESULTS

The composition of these species was analysed by GC-MS, and 65 components were identified. Eucalyptus globulus EO showed a great similarity with EOs from other regions, with 1,8-cineole (79.85%) the major component. Also rich in this constituent was Rosmarinus officinalis (43.99%). However, the chemical profile of Thymus algeriensis was rather different, and for the first time such a high content of borneol (23.48%) has been described in this EO. The antimicrobial activity of these species has also been studied against seven pathogenic and spoiling bacteria of significant importance. According to the results, Thymus algeriensis showed the best bacteriostatic and bactericidal effect, followed by Eucalyptus globulus and Rosmarinus officinalis.

CONCLUSIONS

As far as we know this is the first time that minimum inhibitory and bactericidal concentration values have been reported for Eucalyptus globulus EO. Our data support the possible use of this EO as well as Thymus algeriensis EO, as potential natural agents in preservatives for food and pharmaceutical products.

Antifreeze glycoprotein agents: structural requirements for activity

Antifreeze glycoproteins (AFGPs) are considered to be the most efficient means to reduce ice damage to cell tissues since they are able to inhibit growth and crystallization of ice. The key element of antifreeze proteins is to act in a non-colligative manner which allows them to function at concentrations 300-500 times lowers than other dissolved solutes. During the past decade, AFGPs have demonstrated tremendous potential for many pharmaceutical and food applications. Presently, the only route to obtain AFGPs involves the time consuming and expensive process of isolation and purification from deep-sea polar fishes. Unfortunately, it is not amenable to mass production and commercial applications. The lack of understanding of the mechanism through which the AFGPs inhibit ice growth has also hampered the realization of industrial and biotechnological applications. Here we report the structural motifs that are essential for antifreeze activity of AFGPs, and propose a unified mechanism based on both recent studies of short alanine peptides and structure activity relationship of synthesized AFGPs.

Effect of xylose on the molecular and particle size distribution of peanut hydrolysate in Maillard reaction system

BACKGROUND

The Maillard reaction is a complex series of reactions between reducing sugars and amino groups. Changing any of reaction parameters would alter the reaction pathway. This study investigated the effect of xylose concentration on the molecular and particle size distribution of Maillard reaction products (MRPs) derived from peanut hydrolysate and xylose to discuss their formation mechanism.

RESULTS

Molecular weight and particle size distribution analyses indicated that both peptide degradation and peptide cross-linking occurred during the Maillard reaction. Heat treatment would make the high-molecular-weight peptides degrade into low-molecular-weight peptides and free amino acids. Maillard reaction increased the molecular weight and particle sizes of products as the xylose concentration increased from 1% to 4%.

CONCLUSION

The study shows that both peptide degradation and peptide cross-linking occurred during the Maillard reaction. The thermal degradation product (TDP) and MRPs had significantly different molecular size distribution, and the particle size distribution of TDPs and MRPs had similar change tendency to that of the molecular size distribution. These would provide an insight into the formation mechanism of MRPs.

Antioxidant activity and free radical-scavenging capacity of a selection of wild-growing Colombian plants

BACKGROUND

The replacement of some synthetic food antioxidants by safe natural antioxidants has fostered research on the screening of raw materials to find new vegetable sources of antioxidants. In this study the antioxidant activity of eight wild-growing Colombian plants was assessed by four complementary assays.

RESULTS

An evaluation of the antioxidant activity of ten ethanolic extracts from Baccharis chilco, Cinnamomum triplinerve, Ilex laurina, Lachemilla orbiculata, Lepechinia conferta, Quercus humboldtii, Rubus urticifolius and Tephrosia cinerea was carried out. Furthermore, the total phenolic content was determined by the Folin-Ciocalteu method, and the relationship between phenolic content and activity was also statistically investigated. Cinnamomum triplinerve, L. conferta and I. laurina were found to have the highest phenolic contents. Baccharis chilco, C. triplinerve, I. laurina, L. conferta, Q. humboldtii and R. urticifolius showed higher radical-scavenging activity (DPPH and superoxide assays) than commercial rosemary oleoresin (reference). Lachemilla orbiculata and R. urticifolius showed higher antioxidant activity (β-carotene-bleaching test) than the reference. The protection factor of all studied plant extracts was below that of the reference according to the Rancimat test.

CONCLUSION

On the basis of the results obtained, C. triplinerve, Q. humboldtii and R. urticifolius seem to be the most promising species for further investigation in order to identify the compounds responsible for their activity.

Volatile trans-2-hexenal, a soybean aldehyde, inhibits Aspergillus flavus growth and aflatoxin production in corn

Trans-2-hexenal, a volatile aldehyde, is produced by soybean (Glycine max [L.] Merr) and other plants via the lipoxygenase pathway. In vitro tests showed it significantly (P < 0.001) reduced Aspergillus flavus germinating conidial viability at 10 μM, with approximately 95% viability reduction observed at 20 μM. The viability of nongerminated conidia was not reduced. To test the effectiveness of this volatile to prevent fungal growth in stored corn, trans-2-hexenal was pumped intermittently into glass jars containing corn. Experiments were performed to determine the ability of 2 different pump cycle time-courses to prevent A. flavus growth on sterile corn (23% moisture). Intermittently (30-min pumping period) over 7 d, this volatile was pumped through 350 g of corn kernels inoculated with 1 mL of 3 × 10⁴ conidia of A. flavus. Controls consisted of (1) sterile corn, (2) corn inoculated with A. flavus with no pumped air, and (3) corn inoculated with A. flavus with intermittently pumped air. Aflatoxin B₁ (AFB₁), viability counts, and aldehyde concentration in the headspace were performed in each experiment. To determine whether an increased time period between volatile pumping would prevent A. flavus growth, a 2nd series of experiments were performed that were similar to the 1st series except that trans-2-hexenal (only) was pumped for a 30-min period every 12 h. Experiments were performed 3 times for each time course. Both experiments showed that intermittent pumping of volatile trans-2-hexenal significantly (P < 0.001) prevented A. flavus growth and aflatoxin B₁ production over a 7-d period.

PRACTICAL APPLICATION

Results from this study indicate that intermittent pumping of volatile trans-2-hexenal could be used to protect stored corn from A. flavus growth and aflatoxin contamination.

Physicochemical properties and antimicrobial efficacy of electrostatic complexes based on cationic ε-polylysine and anionic pectin

ε-Polylysine (ε-PL) is a food-grade cationic antimicrobial that is highly effective against a wide range of food pathogens and spoilage organisms. However, its application within foods and beverages is currently limited because of its tendency to associate with anionic substances, thereby increasing product turbidity or forming sediments. In this study, we examined a potential means of overcoming these problems by forming electrostatic complexes between cationic ε-PL and anionic pectin. The nature of the complexes formed depended on the mass ratio of pectin to ε-PL (R(P-PL)), since this determined their electrical characteristics, aggregation stability, and antimicrobial efficacy. The electrical charge on the complexes went from positive to negative with increasing R(P-PL), with the point of zero charge being around R(P-PL) ∼ 8. Soluble complexes or stable colloidal dispersions were formed at low and high R(P-PL) levels, but insoluble complexes were formed at intermediate levels (i.e., 4 ≤ R(P-PL) ≤ 16). The complexes maintained good antimicrobial activity (minimum inhibitory concentration of ε-PL < 10 μg/mL) at R(P-PL) ≤ 20 against two acid resistant spoilage yeasts: Zygosaccharomyces bailli and Saccharomyces cerevisiae. Finally, we showed that certain ε-PL-pectin complexes (10 μg/mL ε-PL; R(P-PL) ≥ 2) could be incorporated into green tea beverages without adversely affecting their appearance or physical stability. This work has shown that the function of a cationic antimicrobial agent (ε-polylysine) can be improved by incorporating it within electrostatic complexes using a food-grade anionic biopolymer (pectin).

Effects of chitin and its derivative chitosan on postharvest decay of fruits: a review

Considerable economic losses to harvested fruits are caused by postharvest fungal decay during transportation and storage, which can be significantly controlled by synthetic fungicides. However, considering public concern over pesticide residues in food and the environment, there is a need for safer alternatives for the control of postharvest decay to substitute synthetic fungicides. As the second most abundant biopolymer renewable source in nature, chitin and its derivative chitosan are widely used in controlling postharvest decay of fruits. This review aims to introduce the effect of chitin and chitosan on postharvest decay in fruits and the possible modes of action involved. We found most of the actions discussed in these researches rest on physiological mechanisms. All of the mechanisms are summarized to lay the groundwork for further studies which should focus on the molecular mechanisms of chitin and chitosan in controlling postharvest decay of fruits.

Comparative antioxidant activity of edible Japanese brown seaweeds

Japanese edible brown seaweeds, Eisenia bicyclis (Arame), Kjellmaniella crassifolia (Gagome), Alaria crassifolia (Chigaiso), Sargassum horneri (Akamoku), and Cystoseira hakodatensis (Uganomoku) were assayed for total phenolic content (TPC), fucoxanthin content, radical scavenging activities (DPPH, peroxyl radical, ABTS, and nitric oxide), and antioxidant activity in a liposome system. Among the solvents used for extraction, methanol was the most effective to extract total phenolics (TPC) from brown seaweeds. Among 5 kinds of brown seaweeds analyzed, methanol extract from C. hakodatensis was the best source for antioxidants. The high antioxidant activity of the extract was based not only on the high content of phenolics, but on the presence of fucoxanthin. No significant correlation (P > 0.05) was observed between TPC per gram extract with DPPH radical scavenging activity of the methanol extracts. These observed discrepancy would be due to structural variations in the phenolic compounds, and different levels of fucoxanthin in the extracts. The present study also demonstrated the synergy in the antioxidant activity of the combination of brown seaweed phenolics and fucoxanthin.

Mung bean trypsin inhibitor is effective in suppressing the degradation of myofibrillar proteins in the skeletal muscle of blue scad (Decapterus maruadsi)

Mung bean trypsin inhibitor (MBTI) of the Bowman-Birk family was purified to homogeneity with a molecular mass of approximately 9 kDa on tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and 8887.25 Da as determined by matrix-assisted laser desorption/ionization-quadrupole ion trap-time-of-flight mass spectrometry (MALDI-QIT-TOF MS). Using blue scad myofibrillar proteins as targets, it was found that, in the absence of MBTI, proteolysis of myofibrillar proteins, especially myosin heavy chain (MHC), could be identified after incubation at 55 °C for 2 h, while in the presence of MBTI, with a final concentration of 25 ng/mL, proteolysis of these proteins was greatly suppressed even after incubation for 3 h. Although cysteine proteinase inhibitor E-64 was also effective in preventing protein degradation, inhibitors for metallo- and asparatic proteinases did not reveal obvious inhibitory effects. Our present results strongly suggested that the naturally occurring legume bean seed protein MBTI can be used as an effective additive in preventing marine fish blue scad surimi gel softening, which is quite possibly caused by myofibril-bound serine proteinase (MBSP).

Structure-activity relationships of polyphenols to prevent lipid oxidation in pelagic fish muscle

The influence of polymerization (number of monomers) and galloylation (content of esterified gallates) of oligomeric catechins (proanthocyanidins) on their effectiveness to prevent lipid oxidation in pelagic fish muscle was evaluated. Non-galloylated oligomers of catechin with diverse mean polymerization (1.9-3.4 monomeric units) were extracted from pine (Pinus pinaster) bark. Homologous fractions with galloylation ranging from 0.25 to <1 gallate group per molecule were obtained from grape (Vitis vinifera) and witch hazel (Hamamelis virginiana). The results showed the convenience of proanthocyanidins with medium size (2-3 monomeric units) and low galloylation degree (0.15-0.25 gallate group/molecule) to inhibit lipid oxidation in pelagic fish muscle. These optimal structural characteristics of proanthocyanidins were similar to those lately reported in fish oil-in-water emulsions using phosphatidylcholine as emulsifier. This finding suggests that the antioxidant behavior of polyphenols in muscle-based foods can be mimicked in emulsions prepared with phospholipids as emulsifier agents. The present data give relevant information to achieve an optimum use of polyphenols in pelagic fish muscle.

Application of lysine, taurine, disodium inosinate and disodium guanylate in fermented cooked sausages with 50% replacement of NaCl by KCl

The effects of 50% replacement of NaCl by KCl and addition of the amino acids lysine and taurine and the 5'-ribonucleotide disodium inosinate and disodium guanylate on some sensory and physicochemical parameters of fermented cooked sausages were evaluated. The partial replacement of NaCl by KCl did not alter the manufacturing process; however, defects in the sensory quality were detected. Lysine at a concentration of 0.313% and a mixture of taurine (750 mg/kg) with disodium inosinate (300 mg/kg) and disodium guanylate (300 mg/kg) reduced the sensory defects caused by KCl, allowing the fermented cooked sausages to be elaborated with reduced sodium content and high sensory quality.

Surface treatments and coatings to maintain fresh-cut mango quality in storage

BACKGROUND

Edible coatings may extend fresh-cut fruit storage by preventing moisture loss and decreasing gas exchange. This study evaluated the effect of an antibrowning dip (calcium ascorbate, citric acid and N-acetyl-L-cysteine), followed or not with carboxymethylcellulose (CMC) or carrageenan coatings on quality of fresh-cut mangoes stored at 5 °C for up to 20 days. A fourth treatment, only used in one of four experiments, consisted of chitosan. Treatments were applied on 'Tommy Atkins', 'Kent' and 'Keitt' mangoes harvested from Homestead (FL), and on imported store-bought mangoes.

RESULTS

The antibrowning dips maintained the best visual quality during storage for all cultivars, as indicated by higher b*, hue and L*. The CMC coating maintained similar visual quality, but carrageenan or chitosan decreased L* and b*. The antibrowning dip containing calcium ascorbate reduced firmness loss on cut pieces of 'Keitt', 'Kent' and store-bought mangoes. The antibrowning treatment maintained higher titratable acidity for 'Kent' and 'Keitt', resulting in lower sensory sweetness.

CONCLUSION

This study with repeated experiments showed that calcium ascorbate with citric acid and N-acetyl-L-cysteine maintained cut mango slices attractiveness in storage by keeping light color in both varieties. The addition of a polysaccharide coating did not consistently improve quality.

Exogenous methyl jasmonate diminishes the formation of lipid-derived compounds in boiled potato (Solanum tuberosum L.)

BACKGROUND

During potato storage the tubers tend to develop off-flavours, mainly due to lipid-derived aldehydes, whose formation is increased after boiling or processing. This may become a problem when boiled or precooked potatoes are used. Methyl jasmonate (MJ) is a phytohormone capable of modifying plant and food composition. The aim of this work was to control the formation of off-flavours in different cultivars of raw potato during storage by MJ treatment.

RESULTS

The use of Carbowax 20M as support in MJ emulsion resulted in significantly (P < 0.05) lower levels of lipid-derived compounds than the use of lanolin. Levels of the lipid-derived aldehydes propanal, hep-2-enal, nonanal, oct-2-enal and hexanal, although dependent on variety, generally decreased significantly (P < 0.05) after treatment with MJ/Carbowax 20M emulsion. Sugar-derived compounds such as pyridine and furfural, however, were not affected by this treatment.

CONCLUSION

Treatment with MJ/Carbowax 20M can be used to diminish the formation of off-flavours in boiled potato. However, this treatment is not useful to avoid the sweetening caused by sugar-derived products. Additional advantages of exogenous MJ are a delay in the appearance of sprouting and aging and hence prolongation of the storage life of potato tubers.

Acids in combination with sodium dodecyl sulfate caused quality deterioration of fresh-cut iceberg lettuce during storage in modified atmosphere package

Recent studies showed that sodium acid sulfate (SAS) and levulinic acid (LA) in combination with sodium dodecyl sulfate (SDS) was effective in inactivating human pathogens on Romaine lettuce. The present study investigated the effects of LA and SAS in combination with SDS (as compared with citric acid and chlorine) on the inactivation of E. coli O157:H7 and sensory quality of fresh-cut Iceberg lettuce in modified atmosphere packages during storage at 4 °C. Results showed that LA (0.5% to 3%) and SAS (0.25% to 0.75%) with 0.05% SDS caused detrimental effects on visual quality and texture of lettuce. LA- and SAS-treated samples were sensorially unacceptable due to development of sogginess and softening after 7 and 14 d storage. It appears that the combined treatments caused an increase in the respiration rate of fresh-cut lettuce as indicated by higher CO(2) and lower O(2) in modified atmosphere packages. On the positive side, the acid treatments inhibited cut edge browning of lettuce pieces developed during storage. LA (0.5%), SAS (0.25%), and citric acid (approximately 0.25%) in combination with SDS reduced population of E. coli OH157:H7 by 0.41, 0.87, and 0.58 log CFU/g, respectively, while chlorine achieved a reduction of 0.94 log CFU/g without damage to the lettuce. Therefore, compared to chlorine, LA and SAS in combination with SDS have limited commercial value for fresh-cut Iceberg lettuce due to quality deterioration during storage.

Gemini alkylammonium salts as biodeterioration inhibitors

To protect materials against biodeterioration, physical, biological or chemical methods can be used. Chemical inhibitors of biodeterioration are the most common and effective. A new class of chemical inhibitors-gemini alkylammonium salts-shows excellent biocidal properties and good ecological profile. These compounds can be applied as biodeterioration inhibitors in a wide variety of materials.

Solid-state NMR spectroscopic studies on the interaction of sorbic acid with phospholipid membranes at different pH levels

2H, 31P, and 1H-magic-angle-spinning (MAS) solid-state NMR spectroscopic methods were used to elucidate the interaction between sorbic acid, a widely used weak acid food preservative, and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayers under both acidic and neutral pH conditions. The linewidth broadening observed in the 31P NMR powder pattern spectra and the changes in the 31P longitudinal relaxation time (T1) indicate interaction with the phospholipid headgroup upon titration of sorbic acid or decanoic acid into DMPC bilayers over the pH range from 3.0 to 7.4. The peak intensities of sorbic acid decrease upon addition of paramagnetic Mn2+ ions in DMPC bilayers as recorded in the 1H MAS NMR spectra, suggesting that sorbic acid molecules are in close proximity with the membrane/aqueous surface. No significant 2H quadrupolar splitting (DeltanuQ) changes are observed in the 2H NMR spectra of DMPC-d54 upon titration of sorbic acid, and the change of pH has a slight effect on DeltanuQ, indicating that sorbic acid has weak influence on the orientation order of the DMPC acyl chains in the fluid phase over the pH range from 3.0 to 7.4. This finding is in contrast to the results of the decanoic acid/DMPC-d54 systems, where DeltanuQ increases as the concentration of decanoic acid increases. Thus, in the membrane association process, sorbic acids are most likely interacting with the headgroups and shallowly embedded near the top of the phospholipid headgroups, rather than inserting deep into the acyl chains. Thus, antimicrobial mode of action for sorbic acid may be different from that of long-chain fatty acids.

Combined use of starter cultures and preservatives to control production of biogenic amines and improve sensorial profile in low-acid salami

The combined effect of starter culture, nitrites, and nitrates has been studied in low-acidity salamis, typical products of northern Italy. Nine batches have been prepared, combining three different inoculations of starter cultures (control, Lactobacillus plantarum , and Lactobacillus plantarum together with Kocuria varians ) with three different preservatives (control, sodium nitrate, and sodium nitrite). All of the batches showed a good fermentation process with a proper pH decrease, which was quicker in batches inoculated with L. plantarum. The use of starter cultures and in particular the use of nitrites allowed the control of the proliferation of Enterobacteriaceae and enterococci. The accumulation of biogenic amines, especially putrescine, cadaverine, tryptamine, and tyramine, in salami ready for consumption (60 days of ripening) was strongly affected by the presence of Enterobacteriaceae and enterococci. Results obtained showed that the combined use of adequate preservatives and starter cultures allows the production of safer products with improved sensorial profile.

Inhibition of Penicillium digitatum and Penicillium italicum by hydroxypropyl methylcellulose-lipid edible composite films containing food additives with antifungal properties

New hydroxypropyl methylcellulose (HPMC)-lipid edible composite films containing low-toxicity chemicals with antifungal properties were developed. Tested chemicals were mainly salts of organic acids, salts of parabens, and mineral salts, classified as food additives or generally recognized as safe (GRAS) compounds. Selected films containing food preservatives were used for in vitro evaluation (disk diameter test) of their antifungal activity against Penicillium digitatum (PD) and Penicillium italicum (PI), the most important postharvest pathogens of fresh citrus fruit. Mechanical properties and oxygen (OP) and water vapor permeabilities (WVP) of selected films were also determined. Film disks containing parabens and their mixtures inhibited PD and PI to a higher extent than the other chemicals tested. Among all organic acid salts tested, potassium sorbate (PS) and sodium benzoate (SB) were the most effective salts in controlling both PD and PI. The use of mixtures of parabens or organic acid salts did not provide an additive or synergistic effect for mold inhibition when compared to the use of single chemicals. Barrier and mechanical properties of films were affected by the addition of food preservatives. Results showed that HPMC-lipid films containing an appropriate food additive should promise as potential commercial antifungal edible coatings for fresh citrus fruit.