Effect of wild strains of Lactococcus lactis on the volatile profile and the sensory characteristics of ewes' raw milk cheese

The production of volatile compounds by wild strains of Lactococcus lactis used as starter cultures and their effect on the sensory characteristics of ewes' raw milk cheese were investigated. Sixteen vats of cheese were manufactured and ripened for 120 d in two experiments, each of them duplicated. In the first experiment, milk was inoculated with different ratios of four wild Lactococcus lactis strains, two producing and two not producing branched-chain volatile compounds, and in the second experiment with different ratios of a commercial starter culture and the two strains producing branched-chain volatile compounds. Cheese pH, proteolysis, and aminopeptidase activity increased when the strains producing branched-chain volatile compounds were inoculated at a higher rate. Fifty volatile compounds were identified in cheeses using a purge and trap system coupled to a gas chromatography-mass spectrometry apparatus. The relative abundances of 30 volatile compounds (8 alcohols, 5 aldehydes, 3 ketones, 12 esters, 1 sulfur compound, and 1 benzenic compound) were influenced by starter culture composition. 2-Methylpropanol, 3-methylbutanol, isobutyl acetate, isoamyl acetate, ethyl butyrate, isobutyl butyrate, and isoamyl butyrate were always more abundant in the cheeses made with a higher level of L. lactis strains producing branched-chain volatile compounds. Flavor intensity was enhanced by a high level of L. lactis strains producing branched-chain volatile compounds in the first experiment, in which four wild L. lactis strains were used as starter culture, but not in the second experiment, in which a combination of two wild L. lactis strains and the commercial starter culture were used. Flavor quality, as judged by trained panelists, was impaired in both experiments by a high level of L. lactis strains producing branched-chain volatile compounds.     

Short communication: Chemical-sensory and volatile compound characterization of ricotta forte,a traditional fermented whey cheese

Ricotta forte is a traditional whey cheese, obtained through natural fermentation of fresh ricotta, that is getting increasing attention by food traders. In view of possible initiatives for its valorization, the chemical and sensory characteristics were investigated. Samples were obtained from 14 different manufacturer, and were subjected to chemical, biochemical, volatile organic compound, and sensory analyses. All samples presented low pH with high moisture (62–66%) and fat content (57–60% on dry matter). From a biochemical point of view, the electrophoretic patterns evidenced that β-lactoglobulin was the main protein present at all sample ages. Only intermediate levels of proteolysis (20.69% ripening index) took place during aging, whereas the main biochemical event in this dairy product was lipolysis (2.10 mEq/g of acid degree value). Accordingly, free fatty acids dominated the volatile organic compound profile and strongly influenced the sensory characteristics with flavor described as rancid, pungent, acrid, and smelly feet: all associated with short-chain fatty acids such as acetic, propionic, butyric, and caproic. Finally, the sample age did not influence chemical composition, whereas it had significant effect on lipolysis and flavor intensity.     

Effect of denatured whey protein concentrate and its fractions on cheese composition and rheological properties

The objectives of this study were (1) to assess the effect of a denatured whey protein concentrate (DWPC) and its fractions on cheese yield, composition, and rheological properties, and (2) to separate the direct effect of the DWPC or its fractions on cheese rheological properties from the effect of a concomitant increase in cheese moisture. Semihard cheeses were produced at a laboratory scale, and mechanical properties were characterized by dynamic rheometry. Centrifugation was used to induce a moisture gradient in cheese to separate the direct contribution of the DWPC from the contribution of moisture to cheese mechanical properties. Cheese yield increased and complex modulus (G*) decreased when the DWPC was substituted for milk proteins in milk. For cheeses with the same moisture content, the substitution of denatured whey proteins for milk proteins had no direct effect on rheological parameters. The DWPC was fractionated to evaluate the contribution of its different components (sedimentable aggregates, soluble component, and diffusible component) to cheese yield, composition, and rheological properties. The sedimentable aggregates were primarily responsible for the increase in cheese yield when DWPC was added. Overall, moisture content explained to a large extent the variation in cheese rheological properties depending on the DWPC fraction. However, when the effect of moisture was removed, the addition of the DWPC sedimentable fraction to milk increased cheese complex modulus. Whey protein aggregates were hypothesized to act as active fillers that physically interact with the casein matrix and confer rigidity after pressing.     

Comparative studies on lipid oxidation of organic model sausage without nitrite produced with the addition of native or autoclaved mustard seed and acid whey

The objective of this work was to evaluate the influence of the addition of native and autoclaved mustard seed (AMS) with combination of acid whey (AW) on the stability of organic model sausages during 30 days of vacuum storage by measuring primary and secondary products of lipid oxidation, the changes in the fatty acid composition, oxidation–reduction potential and antioxidant capacity. Briefly, the addition of AW (5%) with combination of AMS (1%) significantly increased the capacity of sausages to capture the radical cations 2,2‐azinobis(3‐ethyl‐benzothiazoline)‐6‐sulphonate at 1 day of storage which suggests that autoclaved mustard possessed significantly higher amount of phenolic acids compared with native mustard. The salted samples with mustard seed addition characterised by lower oxidation–reduction potential values (264.5–302.1 mV) during the whole storage period compared with control‐cured sample (307.3–330.5 mV). Results of conjugated dienes (CD) measurements indicated that salted meat product samples with mustard seed addition were characterised by significantly lower CD concentration (1.12–1.90 μmol mg^?1 meat product) compared with control‐cured sample (1.86–2.55 μmol mg^?1 meat product). The AW and mustard seed added to uncured sausage were able to protect polyunsaturated fatty acids against the oxidation comparable to nitrite.     

Effect of different fibres on texture,rheological and sensory properties of acid casein processed cheese sauces

The objective of this study was the evaluation of different fibres (bamboo, acacia, potato or citrus) addition on texture, rheological and sensory properties of acid casein processed cheese sauces. Fibres used in production of sauces had an impact on the texture, viscosity, viscoelastic and sensory properties. The largest increase in viscosity was observed in products with addition of potato fibre, which have good water holding and adsorption capacity. Processed cheese sauce with the addition of citrus fibre was characterised by the highest values in general, and the increase of this feature in the tested samples was regular. Adhesiveness was the highest in products with 1% addition of every fibre. The lowest values of viscosity single shear, G′ and G″ moduli, among all tested, had sauces with acacia fibre. Moreover, they had the most thin liquid consistency, which was different from preferred one.     

Effect of fermentation on biochemical and sensory characteristics of millet flour supplemented with whey protein

Pearl millet like other cereals shows qualitative and quantitative deficiency in protein. The main objective of this study was to obtain the food of high nutritive value with high protein content and biological value by supplementing pearl millet, with whey protein. Two levels of whey protein were considered (20% and 25% protein content). Supplemented samples and control were fermented in the presence of starter for 14 h according to the traditional method utilised in Sudan. The pH, crude protein, in vitro protein digestibility (IVPD) and protein fractions of the fermented and supplemented pearl millet were determined at 2‐ h intervals. Supplementation of whey protein resulted in significant increase in protein content compared to the control, i.e. 14.8%, 23.9% and 28.7% for Ashana control (AC), Ashana plus whey protein (20% protein content) (AW₁) and Ashana plus whey protein (25% protein content) (AW₂), respectively. Fermentation was found to cause a highly significant (P ≤ 0.05) improvement in IVPD for AC, AW₁ and AW_2. The major protein fraction in the whey protein supplemented doughs was the globulin. This would indicate an improvement in the nutritional quality of pearl millet. Sensory evaluation revealed higher acceptability for whey protein supplemented formulas compared to control.