Effects of co-inoculation and sequential inoculation of Tetragenococcus halophilus and Zygosaccharomyces rouxii on soy sauce fermentation

The use of Tetragenococcus halophilus and Zygosaccharomyces rouxii as starter cultures is essential for desirable volatiles production during moromi stage of soy sauce fermentation. In this study, the effect of simultaneous and sequential inoculation of cultures in moromi fermentation models, with respect to viability, physicochemical changes, and volatiles formation (using SPME-GC/MS) was investigated. Interestingly, an antagonism was observed as T. halophilus only proliferated (3 log increase) in the presence of Z. rouxii, while Z. rouxii growth was suppressed by 4 log in concurrence with pH increase to 7.31. Final content of reducing sugars, ethanol, acetic acid, and amino nitrogen did not differ significantly (p < 0.05) between co-inoculation and sequential inoculation. However, Z. rouxii promoted alcohols formation and produced a more complex aroma profile under suppression. According to Principal Component Analysis (PCA), the inoculation sequence (co-inoculation and sequential) has impacts on volatile compound profiles during moromi fermentation

Acid production, growth kinetics and aroma profiles of Lactobacillus flora from Stilton cheese

The effect of Lactobacillus plantarum isolates from Stilton cheese on aroma profiles of milk fermentation was examined. Representative Lb. plantarum isolates were cultured alone and in combination with acid-producing and non-acid producing Lactococcus lactis NCIMB 9918 in UHT milk at 30 & 18oC for 48 h & 12 weeks, respectively in presence and absence of salt, simulating cheese production and ripening. During long-term ripening, Lb. plantarum grew faster when co-cultured with non-acid producing Lc. lactis in the presence of salt. One isolate of Lb. plantarum produced the highest concentration of alcohols, organic acids and acetoin. Co-culture of Lb. plantarum with acid-producing Lc. lactis enhanced acid and alcohol production, whereas co-inoculation with non-acid producing Lc. lactis increased acetoin synthesis. Lb. plantarum is an incidental organism in cheese and its presence is unpredictable. Occurrence of different genotypes of Lb. plantarum could contribute to batch to batch variation in the cheese aroma characteristics

Modulating the release of Escherichia coli in double W1/O/W2 emulsion globules under hypo-osmotic pressure

Bacterial release from double W1/O/W2 emulsion globules under hypo-osmotic pressure is described for the first time.</p

Physico-chemical, antimicrobial and antioxidant properties of gelatin-chitosan based films loaded with nanoemulsions encapsulating active compounds

The aim of this research was to develop and characterize gelatin-chitosan (4:1) based films that incorporate nanoemulsions loaded with a range of active compounds; N1: canola oil; N2: α-tocopherol/cinnamaldehyde; N3: α-tocopherol/garlic oil; or N4: a-tocopherol/cinnamaldehyde and garlic oil. Nanoemulsions were prepared in a microfluidizer with pressures ranging from 69 to 100 MPa, and 3 processing cycles. Films were produced by the casting method incorporating 5 g N1,2,3,4/100 g biopolymers and using glycerol as a plasticizer, and subsequently characterized in terms of their physico-chemical, antimicrobial and antioxidant properties. No differences (p > 0.05) were observed for all films in terms of moisture content (18% w/w), and thermal properties. The films' solubility in water and light transmission at 280 nm were considerably reduced as compared to the control, N1 (15% and 60% respectively) because of the nanoemulsion incorporation. The film loaded with N1 showed the greatest (p < 0.05) opacity, elongation at break and stiffness reduction, and was the roughest, whilst the lowest tensile strength and ability to swell were attained by films loaded with N3 and N4, respectively. DSC and X-ray analyses suggested compatibility among the biopolymeric-blend, and a good distribution of nanodroplets embedded into the matrix was confirmed by AFM and SEM analyses. Films loaded with nanoencapsulated active compounds (NAC) were very effective against Pseudomonas aeruginosa, and also showed high antioxidant activity. Overall, the present study offers clear evidence that these active-loaded films have the potential to be utilized as packaging material for enhancing food shelf life

Water-in-oil-in-water double emulsion for the delivery of starter cultures in reduced-salt moromi fermentation of soy sauce

This study investigated the application of water-oil-water (W1/O/W2) double emulsions (DE) for yeast encapsulation and sequential inoculation of Zygosaccharomyces rouxii and Tetragenococcus halophilus in moromi stage of soy sauce fermentation with reduced NaCl and/or substitution with KCl. Z. rouxii and T. halophilus were incorporated in the internal W1 and external W2 phase of DE, respectively. NaCl reduction and substitution promoted T. halophilus growth to 8.88 log CFU/mL, accompanied with faster sugar depletion and enhanced lactic acid production. Reducing NaCl without substitution increased the final pH (5.49) and decreased alcohols, acids, esters, furan and phenol content. However, the application of DE resulted in moromi with similar microbiological and physicochemical characteristics to that of high-salt. Principal component analysis of GC–MS data demonstrated that the reduced-salt moromi had identical aroma profile to that obtained in the standard one, indicating the feasibility of producing low-salt soy sauce without compromising its quality

Flavour production of Stilton blue cheese microflora

In the blue cheese Stilton the starter mould Penicillium roqueforti grows and sporulates during the ripening period and is considered to be responsible for the unique blue cheese aroma. However, the sporulation of the mould, which results in the formation of blue veins, takes place in a fraction of the Stilton matrix which overall is very heterogeneous. Most blue cheeses develop a secondary microflora of yeasts which may affect their aroma. The aim of this study was to investigate the yeast flora of Stilton, the aroma profile of the cheese and the role of the yeasts in the aroma production. The approach in this work was to study individually the different sections of Stilton (the blue veins, the white core and the outer crust) as previous studies have demonstrated each section has a differing bacterial flora. In addition to the classical microbiology, a series of molecular techniques (Denaturing Gradient Gel Electrophoresis, Restriction Fragment Length Polymorphism and Terminal RFLP) were compared and applied for the screening of the local fungal communities in the cheese. The results showed that the two approaches were complementary. It was concluded that the structure of the fungal community was different for each section of the cheese. The aroma profiles of the three different sections of Stilton were studied using solvent extraction Gas Chromatography-Mass Spectrometry (GC-MS), a headspace GC-MS technique (SPME GC-MS) and direct headspace analysis (Atmospheric Pressure Chemical Ionisation [APCI]-MS). The different sections of Stilton presented different aroma profiles. Overall, the blue and the outer crust had similar profiles. These two sections contained higher amount of ketones while the white contained higher amounts of alcohols and aldehydes. Yeast isolates and the starter Penicillium roqueforti were cultivated alone and in combination in a cheese model and the aroma production was studied with SPME GC-MS analysis. The co-culture of the starter Penicillium roqueforti and individual yeast isolates resulted in aroma profiles different from those that were produced by the mould or the yeasts individually. The model of Penicillium roqueforti with Yarrowia lipolytica resulted in an aroma more similar to blue cheese than produced by the mould alone. Sensory analysis (Flash profile technique) was used in order to compare the aroma of this model with the aroma of blue cheeses and the perception of the combined culture was found to be similar to Stilton cheese, whereas that of the mould alone was not. Yeasts are a significant part of the microflora of Stilton and they are able to affect the aroma production. Selected isolates of Yarrowia lipolytica could be used in combination with Penicillium roqueforti for the production of blue cheese aroma e.g. as a starter culture.EThOS - Electronic Theses Online ServiceGBUnited Kingdo