White Brined Cheese Production by Incorporation of a Traditional Milk-Cereal Prebiotic Matrix with a Candidate Probiotic Bacterial Strain

The aim of the present study is the evaluation of a novel potentially probiotic Lactobacillus paracasei SP5, previously isolated from dairy products, as a starter culture of white brined cheese production, either free or immobilized on a traditional food, “trahanas”, in order to provide protection to the starter culture and a prebiotic effect. All produced cheeses were compared with cheese manufactured by renin enzyme. Several parameters that affect the acceptability, quality, and shelf life of white brined cheese were investigated, including microbial populations, physicochemical characteristics, and cheese volatiles through 70 days of ripening and storage. White brined cheese production by free or immobilized L. paracasei SP5 resulted in significantly higher acidity (over 0.8 g of lactic acid/100 g of cheese at the 70th day of ripening) and significantly reduced counts (around 50%) of coliforms, yeasts, and fungi compared to cheese produced with no starter culture. The use of the freeze-dried novel starter culture, either free or immobilized, improved the aromatic profile of cheeses as was proven through a GC-MS analysis. In addition, it should be underlined that the application of the novel strain led to white brined cheese with improved overall quality and sensory characteristics. The results indicate the potential industrial use of freeze-dried L. paracasei SP5 as a starter culture for the production of good-quality functional white brined cheeses.

Application of vacuum solid-phase microextraction for the analysis of semi-hard cheese volatiles

Solid-phase microextraction (SPME) is a well-established technique in the analysis of food volatile compounds, usually performed for qualitative analysis. This paper presents an elaboration of conditions for SPME analysis of main volatile compounds in hard cheese and an evaluation of suitability of vacuum to improve the transfer of volatile compounds towards SPME fiber. Compounds representing the main groups of hard cheese volatiles were investigated: 1-pentanol, butanoic acid, 2,3-butanedione and 2-heptanone. Parameters for SPME extraction (temperature, water, sodium carbonate addition, time, vacuum) were evaluated. Application of vacuum had a positive effect on all analytes when extraction was performed from water, but in the cheese matrix the effect was significant only for butanoic acid. Extraction time was the most significant factor for extraction efficiency in examined cheeses, while temperature had a minor effect on the amount of extracted volatiles. The method was applied on Edam, Emmentaler, Gouda and Maasdam cheeses obtained from the market.

Employment of L. paracasei K5 as a Novel Potentially Probiotic Freeze-Dried Starter for Feta-Type Cheese Production

In the present study, a novel potentially probiotic Lactobacillus paracasei strain, previously isolated from dairy products, was evaluated as a starter culture of Feta-type cheese production. Targeting industrial applications, the starter culture was applied as a ready-to-use freeze-dried culture that was either free or immobilized. The immobilized biocatalyst composed of Lactobacillus paracasei K5 cells absorbed within delignified wheat bran prebiotic carrier. All produced cheeses were compared with cheese manufactured by renin enzyme. Several parameters that affect acceptability, quality and shelf-life of Feta-type cheese were investigated, including microbial populations, physicochemical characteristics and cheese volatiles through 90 days of ripening and storage. Survival of L. paracasei K5 remained in high levels (≥6.0 log cfu/g) after the 90th day of cheese production, as recorded by combining microbiological enumeration and strain-specific multiplex PCR analysis. The use of the freeze-dried novel starter culture (free or immobilized) enhanced the aromatic profile of Feta-type cheeses. Finally, the use of the potentially synbiotic immobilized biocatalyst further improved aromatic characteristics of produced cheese and decrease of possible spoilage or pathogenic microorganisms. These findings indicate the potential industrial use of freeze-dried L. paracasei K5 as starter culture for the production of good-quality functional Feta-type cheese.

The Flavor Property of Soft Cheese Fermented by Two Stains of Streptococcus thermophilus and Made of Reconstituted Milk

The effect of reconstituted milk inoculation with Streptococcus thermophilus TM11 and Streptococcus thermophilus SP 1.1 on soft cheese volatiles was investigated. The impact flavors of 2,3-butanedione, 2,3-pentanedione, ethyl acetate, methyl butyrate, ethyl butyrate, butyl acetate and butyric acid were only detected in the fermented cheeses. Levels of diketones were higher in the cheeses fermented by mixed cultures than single culture, while levels of esters except ethyl acetate and butyl acetate showed an opposite tendency. There was significant difference in the levels of 2-hexenal and 2-nonenal among the cheeses. Other compounds originated from lipid oxidation, Strecker degradation, biosynthesis and forages were not significantly influenced by milk inoculation with Streptococcus thermophilus.

Behavioural and electrophysiological responses of the female malaria mosquitoAnopheles gambiae(Diptera: Culicidae) to Limburger cheese volatiles

Limburger cheese, previously shown to attract femaleAnopheles gambiaeGiles, was solvent extracted and chemically fractionated into acid and non-acid fractions. The extracts and aliquots of headspace odour of the cheese were analysed by gas chromatography and electron impact mass spectrometry. Nineteen saturated and unsaturated aliphatic fatty acids, ranging in carbon chain length from C2to C18, were detected. The most abundant acids (>1 mg/g of cheese) identified in the acid extract were ethanoic, propanoic, butanoic, hexadecanoic and 9-octadecenoic acid. The same compounds were identified in analyses of headspace samples but only trace quantities of the less volatile acids (C10to C16) were present, whilst C18acids were absent. Behavioural responses of femaleA. gambiaetowards a range of dilutions of the acid extract (in diethyl ether) were recorded in a windtunnel bioassay. The undiluted extract was found to be repellent, but became highly attractive (P«0.001) at lower doses, and was still significantly attractive (P<0.001) when diluted 106times. A synthetic mixture of 12 of the more abundant aliphatic acids identified in the acid extract was found to be significantly attractive (P<0.001) when diluted 108times. Electroantennographic (EAG) studies showed significant and reproducible responses to (saturated) Limburger cheese headspace. At doses higher than 0.1%, the synthetic mixture of 12 acids elicited significantly higher EAG amplitudes than the solvent control (paraffin oil). EAG responses were recorded from mosquitoes stimulated with C5to C8acids, that were characterized by significant dose-dependencies. Weaker, though significant EAG responses were obtained with the less volatile acids (C9to C14). Only hexadecanoic acid did not elicit a detectable response. The electrophysiological and behavioural responses obtained with fatty acids isolated from Limburger cheese suggests that together they could act as a kairomone for femaleA. gambiae. The implications of this are discussed together with the occurrence and bacterial production of these compounds on human skin.