Effect of forage type, season, and ripening time on selected quality properties of sheep milk cheese

Autochthonous cultures to improve the quality of PGI Castellano cheese: Impact on proteolysis, microstructure and texture during ripening

The aim of this research was to find out the effect of different combinations of starter and non-starter cultures on the proteolysis of Castellano cheese during ripening. Four cheese batches were prepared, each containing autochthonous lactobacilli and or Leuconostoc, and were compared with each other and with a control batch, that used only a commercial starter. To achieve this, nitrogen fractions (pH 4.4-soluble nitrogen and 12 % trichloroacetic acid soluble nitrogen, polypeptide nitrogen and casein nitrogen), levels of free amino acids and biogenic amines were assessed. Texture and microstructure of cheeses were also evaluated. Significant differences in nitrogen fractions were observed between batches at different stages of ripening. The free amino acid content increased throughout the cheese ripening process, with a more significant increase occurring after the first 30 days. Cheeses containing non-starter lactic acid bacteria exhibited the highest values at the end of the ripening period. Among the main amino acids, GABA was particularly abundant, especially in three of the cheese batches at the end of ripening. The autochthonous lactic acid bacteria were previously selected as non-producers of biogenic amines and this resulted in the absence of these compounds in the cheeses. Analysis of the microstructure of the cheese reflected the impact of proteolysis. Additionally, the texture profile analysis demonstrated that the cheese's hardness intensified as the ripening period progressed. The inclusion of autochthonous non-starter lactic acid bacteria in Castellano cheese production accelerated the proteolysis process, increasing significantly the free amino acids levels and improving the sensory quality of the cheeses.

Chemical Safety and Quality Attributes of Dried Sausage Snacks Stored in Modified Atmosphere

A sausage snack was produced by air blast drying of cottage sausage, and its safety and quality were investigated during 10-week storage period in a modified atmosphere (20% CO₂/80% N₂) at 4 ± 1°C and 20 ± 1°C. The results of a sensory and instrumental evaluation of colour and texture showed that significantly greater changes in these parameters were caused by drying the sausage rather than during subsequent storage of the produced snacks. Although total viable count increased and reached a maximum value of 6.5 log CFU g^-1 after 70 days of storage at 20 ± 1°C, Enterobacteriaceae were not detected. The histamine level was approx. 18 mg kg^-1, while the average content of the other biogenic amines after 70 days of storage ranged from 4.4 mg kg^-1 (cadaverine) to 32.1 mg kg^-1 (tyramine). The biogenic amine index was small and varied from 34.5 mg kg^-1 (in the sausage before drying) to 73.4 mg kg^-1 (at the end of the snack storage at 20 ± 1°C). The lipid hydrolysis and oxidation proceeded slowly and did not pose a threat to the product quality. The combination of drying and modified atmosphere packaging maintains good quality and safety of sausage snack during 70 days at refrigerated storage and/or 4 weeks at room temperature.

Relationship between the Dynamics of Gross Composition, Free Fatty Acids and Biogenic Amines, and Microbial Shifts during the Ripening of Raw Ewe Milk-Derived Idiazabal Cheese

This study reports for the first time the relationship between bacterial succession, characterized by high-throughput sequencing (sequencing of V3-V4 16S rRNA regions), and the evolution of gross composition, free fatty acids (FFAs) and biogenic amines (BAs) during cheese ripening. Specifically, Idiazabal PDO cheese, a raw ewe milk-derived semi-hard o hard cheese, was analysed. Altogether, 8 gross parameters were monitored (pH, dry matter, protein, fat, Ca, Mg, P and NaCl) and 21 FFAs and 8 BAs were detected. The ripening time influenced the concentration of most physico-chemical parameters, whereas the producer mainly affected the gross composition and FFAs. Through an O2PLS approach, the non-starter lactic acid bacteria Lactobacillus, Enterococcus and Streptococcus were reported as positively related to the evolution of gross composition and FFAs release, while only Lactobacillus was positively related to BAs production. Several environmental or non-desirable bacteria showed negative correlations, which could indicate the negative impact of gross composition on their growth, the antimicrobial effect of FFAs and/or the metabolic use of FFAs by these genera, and their ability to degrade BAs. Nonetheless, Obesumbacterium and Chromohalobacter were positively associated with the synthesis of FFAs and BAs, respectively. This research work provides novel information that may contribute to the understanding of possible functional relationships between bacterial communities and the evolution of several cheese quality and safety parameters.

The “Crosstalk” between Microbiota and Metabolomic Profile of Kefalograviera Cheese after the Innovative Feeding Strategy of Dairy Sheep by Omega-3 Fatty Acids

The purpose of this study was to examine the effects of two different feeding systems, a control or a flaxseed and lupin diet (experimental), for a sheep flock, on the microbiota and metabolome of Kefalograviera cheese samples produced by their milk. In particular, the microbiota present in Kefalograviera cheese samples was analyzed using 16S rRNA gene sequencing, while ultra-high performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) was applied to investigate the chemical profile of the cheeses, considering the different feeding systems applied. The metagenomic profile was found to be altered by the experimental feeding system and significantly correlated to specific cheese metabolites, with Streptococcaceae and Lactobacillaceae establishing positive and negative correlations with the discriminant metabolites. Overall, more than 120 features were annotated and identified with high confidence level across the samples while most of them belonged to specific chemical classes. Characteristic analytes detected in different concentrations in the experimental cheese samples including arabinose, dulcitol, hypoxanthine, itaconic acid, L-arginine, L-glutamine and succinic acid. Therefore, taken together, our results provide an extensive foodomics approach for Kefalograviera cheese samples from different feeding regimes, investigating the metabolomic and metagenomic biomarkers that could be used to foresee, improve, and control cheese ripening outcomes, demonstrating the quality of the experimental Kefalograviera cheese.

The Effect of Freezing Sheep's Milk on the Meltability, Texture, Melting and Fat Crystallization Profiles of Fresh Pasta Filata Cheese

Simple Summary

Sheep’s milk is usually produced on small farms. It is mainly used in the pro duction of cheese products. One of the methods of extending the shelf life of sheep’s milk is freezing it. In this study we examined the effect of freezing on sheep’s milk and a mixture of sheep’s and cow’s milk on the quality of fresh pasta filata cheeses produced from the milk. It has been proven that the freezing of milk affects the possibility of using it in later cheese processing. Freezing sheep’s milk influenced, among others, a greater hardness and less elasticity of the cheese. We also noticed that the addition of frozen sheep’s milk caused consumer dissatisfaction.

Abstract

Sheep’s milk is produced in smallholdings, which hinders the continuity of production. Therefore, freezing during periods of high production can be a solution. Herein, we examined the effect of freezing on sheep’s milk and a mixture of sheep and cow’s milk (70:30, v/v) on the quality of fresh pasta filata cheeses produced from the milk. Frozen/thawed sheep’s milk contributes little to the development of innovative and reformulated cheeses. This was due to 24% higher hardness and greater extensibility and cutting force, as well as lower stretching and elasticity. Although their flowability increased (Oiling-off from 3 to 12%), the meltability (tube test, and Schreiber test) decreased. Additionally, the use of frozen milk caused consumer dissatisfaction. The consumer penalty analysis of the just–about–right showed that freezing of the milk caused the loss of the refreshing, elasticity and shininess of pasta filata cheeses.