Conjugated Linoleic Acid Content of Cheddar-type Cheeses as Affected by Processing

Factors influencing conjugated linoleic acid content of dairy products: challenges and strategies

Conjugated linoleic acid (CLA), a bioactive fatty acid that provides various physiological benefits, has gained increasing attention in the food industry, and various studies have focused on enhancing its content in dairy products. The factors influencing CLA content in dairy products vary significantly, including lactation stage, breed type, seasonality, feed, management methods of the animals, the manufacturing processes, storage, and ripening periods of the product. Additionally, the incorporation of CLA-producing probiotic bacteria, such as Lactobacillus, Lactococcus, Bifidobacterium, and Propionibacterium, is an emerging study in this field. Studies have revealed that factors affecting the CLA content in milk affect that in dairy products as well. Furthermore, the species and strains of CLA-producing bacteria, fermentation conditions, ripening period, and type of dairy product are also contributing factors. However, production of CLA-enhanced dairy products using CLA-producing bacteria while maintaining their optimal viability and maximizing exposure to free linoleic acid remains limited. The current review emphasized the factors affecting the CLA content and related mechanisms, challenges in the application of CLA-producing probiotic bacteria, and strategies to address these challenges and enhance CLA production in dairy products. Therefore, the development of functional dairy products with enhanced CLA levels is expected to be possible.

Production of conjugated linoleic acid by lactic acid bacteria; important factors and optimum conditions

Conjugated linoleic acid (CLA) has recently attracted significant attention as a health-promoting compound. CLA is a group of positional isomers of linoleic acid (LA) with a conjugated double bond naturally occurring in dairy and ruminant meat products. Microbial biosynthesis of CLA is a practical approach for commercial production due to its high safety and purity. There are some factors for the microbial CLA production such as strain type, microbial growth phase, pH, temperature and incubation time, based on which the amount and type of CLA can be controlled. Understanding the interplay of these factors is essential in optimizing the quantity and composition of microbial CLA, as discussed in the current study. Further exploration of CLA and its influences on human health remains a dynamic and evolving area of study.

Role of Feeding and Novel Ripening System to Enhance the Quality and Production Sustainability of Curd Buffalo Cheeses

The buffalo dairy sector is extending its boundaries to include new buffalo cheese productions beyond mozzarella, overcoming some barriers that make cheeses expensive and unsustainable. This study aimed to evaluate the effects of both the inclusion of green feed in the diet of Italian Mediterranean buffaloes and an innovative ripening system on buffalo cheese quality, providing solutions capable of guaranteeing the production of nutritionally competitive and sustainable products. For this purpose, chemical, rheological, and microbiological analyses were carried out on cheeses. Buffaloes were fed with or without the inclusion of green forage. Their milk was used to produce dry ricotta and semi-hard cheeses, ripened according to both respective traditional (MT) and innovative methods (MI); these are based on automatic adjustments of climatic recipe guided by the continuous control of pH. Green feed enhances the nutritional profile of the final products (high content of MUFAs and PUFAs). As far as the ripening method is concerned, to our knowledge, this is the first study that tests aging chambers, commonly used for meat, for the maturing of buffalo cheeses. Results pointed out the MI validity also in this field of application, as it shortens the ripening period without negatively compromising any of desirable physicochemical properties and the safety and hygiene of the final products. Conclusively, this research highlights the benefits of diets rich in green forage on productions and provides support for the ripening optimization of buffalo semi-hard cheeses.

Effect of forage type in the ovine diet on the nutritional profile of sheep milk cheese fat

The high nutritional value of sheep milk can be advantageous in the manufacture of cheese, and fat plays an important role in sheep cheese properties. The aim of this study was to investigate the effect of feeding common hay or silage diets used in commercial farms on the nutritional value of sheep cheese fat. We also monitored the effect of cheese ripening period on the fatty acid profile. Cheeses were produced from milk of sheep fed hay and silage diets from 8 farms, on 4 separate occasions (February, May, August, and November) over a 1-yr period. Eighty-four individual fatty acids were determined and identified by gas chromatography. Ripening time (100 and 180 d) significantly reduced moisture, acidity, and water activity of cheeses but did not affect the fatty acid content. However, hay feeding, compared with silage feeding, led to cheeses with 1.5- and 1.3-fold higher contents of vaccenic acid and conjugated linoleic acid, without detrimental changes in saturated and n-3 (omega-3) fatty acid composition. Hay forages could be a low-cost alternative for producing cheese with a fatty acid profile suitable for human health, which is an aspect of great interest to the food industry.

Both low- and regular-fat cheeses mediate improved insulin sensitivity and modulate serum phospholipid profiles in insulin-resistant rats

Dietary recommendations for cheese usually promote low (LOW)- over regular (REG)-fat versions due to the saturated fat. Conversely, epidemiological evidence shows that cheese consumption associates with reduced risk of type 2 diabetes. To investigate how cheese influences diabetes-related outcomes, a feeding trial comparing LOW and REG cheese was conducted in high-fat, lard-based diet (HFD)-fed insulin-resistant rats followed by evaluation of potential mechanisms. After 4 weeks of HFD, LOW or REG was added at 7 and 10 g/100 g diet, respectively, for another 8 weeks. Following either an oral glucose or insulin tolerance test to assess glucoregulation, rats were euthanized and serum was collected for metabolomic and lipid analyses. Hepatic tissue was used to measure glucoregulatory enzymes and lipid content. Both LOW and REG improved insulin sensitivity without effect on oral glucose tolerance, insulin secretion or body weight. Serum metabolomics identified 33 metabolites of interest, with 21 being phosphatidylcholines (PCs) or lysophosphatidylcholines (LPCs). HFD rats had significantly reduced LPC C16:1, C17:0, C18:1, C20:3 and C24:0, and these effects were normalized by LOW or REG cheese. Fourteen PC species were lowest in the HFD group and normalized by cheese feeding. Serum choline was elevated sevenfold in HFD- but not cheese-fed rats compared with rats fed low-fat diet. Liver triglyceride was elevated by LOW feeding. In conclusion, inclusion of both LOW and REG cheeses in the diet of insulin-resistant rats improves in vivo glucoregulation. This is associated with altered phospholipid metabolism, including cheese-mediated normalization of species that are decreased by high-fat feeding.

Effect of rearing system (mountain pasture vs. indoor) of Simmental cows on milk composition and Montasio cheese characteristics

Dairy cattle in the Alps are traditionally maintained on high altitude pastures during summer. In recent decades, however, many farmers prefer to maintain the cows always indoor with a hay-based diet. Many authors have shown that the forage type is able to modify the characteristics of milk and cheese. Recently the product specification of PDO Montasio allowed differentiation between mountain cheeses and other products. Aim of this trial is to study the effect of rearing system on the characteristics of milk and cheese produced in this context. One hundred and twenty Simmental dairy cows were considered, 60 grazed on high altitude pasture, and 60 kept indoor and fed a hay-based diet. Cheese production was repeated in two periods (early July and late August) and ripened two and six months. Pasture-derived milk and cheese presented higher fat and lower protein content than hay-derived ones. Rearing systems also affected cheese colour. Textural parameters, hardness, gumminess and chewiness were found to be higher in pasture-derived cheese. In addition, it showed lower level of total saturated fatty acids, and higher level of mono and polyunsaturated fatty acids than hay-derived cheeses. Consumers perceived the difference of cheeses in terms of colour and holes, but they express a similar overall liking. More limited effects of period and ripening time were observed.

Physiological properties of milk ingredients released by fermentation

The demand for health-promoting food ingredients rises within an increasing market worldwide. Different milks fermented with bacteria, yeasts, moulds or enzymes from animal, plant and microbial sources offer a broad range of possibilities to cover different health aspects with new bioactive components. By the fermentation process interesting ingredients are enriched and released from the matrix, like lactoferrin, micro-nutrients, CLA and sphingolipids or synthesized, such as exo-polysaccharides and bioactive peptides. In particular, milk derived bioactive peptides exert several important health-promoting activities, such as anti-hypertensive, anti-microbial, anti-oxidative, immune-modulatory, opioid and mineral-binding properties. Milk-fermentation processes with probiotic bacteria synergistically combine health supporting bacterial and milk ingredient aspects which include new therapeutic solutions concerning hypercholesterolemia, carcinogenic intoxications, treatment of diarrhea, reduction of intestine pathogens, and supporting natural immune defense. Especially, milk-proteins and associated bioactive peptides released during microbial or enzymatic fermentation of milk offer a broad spectrum of new functional properties, for instance anti-hypertensive, anti-microbial, anti-oxidative, immuno-modulatory, opioid and mineral-binding properties. This review aimed at discussing recent research activities on physiological purposes and technical process aspects of functional components from fermented milk with a specific focus on biofunctional peptides released from fermented milk proteins.

Changes in fatty acid profile of feta cheese including conjugated linoleic acid

BACKGROUND

During the last two decades much attention has been given to conjugated linoleic acid (CLA) because of its potentially beneficial biological effects. Cheese is one of the major dietary sources of CLA. However, the CLA content of Greek cheeses is variable and affected by many factors. Fatty acid analysis of feta cheese, made of sheep's milk, was conducted at different stages of the manufacturing process in order to monitor and explain fatty acid and especially CLA changes.

RESULTS

CLA content in fresh milk and during the early stages of manufacture was 0.66 ± 0.02 g 100 g⁻¹ fatty acids; it increased during the ripening process (0.75 ± 0.06 g 100 g⁻¹ fatty acids) and decreased during storage (0.52 ± 0.15 g 100 g⁻¹ fatty acids). Saturated fatty acids (SFA), increased after 37 and 48 days of aging, while monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA), showed the opposite tendency.

CONCLUSION

CLA content significantly increased during the ripening stages and decreased during aging (P ≤ 0.05). CLA is not stable during manufacture and storage of feta cheese, a fact which should be resolved, since this biologically active substance can be obtained from the diet.

Especies ibéricas de los géneros <i>Lithurgus</i> Berthold, 1827, <i>Creightonella</i> Cockerell, 1908 y <i>Chalicodoma</i> Lepeletier, 1841 (Hymenoptera, Megachilidae): claves de identificación y nuevos datos de distribución

El presente trabajo, dentro de la revisión que se está realizando sobre la familia Megachilidae en la fauna ibérica, incluye las claves de identificación y aporta nuevos datos de distribución para las especies de tres géneros: Lithurgus (tres especies), Creightonella (una) y Chalicodoma (ocho). Las claves se acompañan de dibujos y fotografías ilustrativos que permiten el reconocimiento tanto de las especies como de las subespecies.

Changes in the milk and cheese fat composition of ewes fed commercial supplements containing linseed with special reference to the CLA content and isomer composition

A study was carried out to increase the CLA contents in ewes' milk fat under field conditions by dietary means and to investigate the extent of the changes and consequences for milk processing and cheese quality. During a 3-mon period, ewes' bulk milk samples were collected every week from two different herds. For the first 4 wk the ewes were fed a conventional diet. Then the following 6 wk a supplement enriched in alpha-linolenate (whole linseed) was incorporated into the ovine diet. Finally, in the last 3 wk the feeding was the same as in the first 4 wk. The FA profile in milk fat was monitored by GC, and the distribution of CLA isomers was thoroughly tested by combining GC-MS of 4,4-dimethyloxazoline derivatives (DMOX) with silver ion-HPLC (Ag(+)-HPLC) of FAME. Reconstructed mass spectral profiles of CLA characteristic ions from DMOX were used to identify positional isomers, and Ag(+)-HPLC was used to quantify them. An increase in total CLA in milk fat was observed, and total CLA remained elevated during the weeks of enriched alpha-linolenate feeding. In our experimental conditions there was a linear relationship between trans-vaccenic acid (trans-11-octadecenoic acid; trans-11 18:1) and 9-cis,11-trans CLA in ewes' milk fat. Concerning the CLA isomer profile, increases in the 11,13- and 12,14-18:2 positional isomers were considerable when linseed was included in the diet. Organoleptic characteristics of cheeses made with CLA-enriched milk did not substantially differ from those made with nonsupplemented ewes' milk. CLA total content and isomer profile did not change during ripening.

The composition of bovine milk lipids: January 1995 to December 2000

Data from recent publications on bovine milk lipids are presented and discussed. This includes extraction of lipids, triacylglycerols, phospholipids, other complex lipids, sterols, isoflavones, and fatty acids. Improved gas-liquid and high performance liquid chromatography were used. Data on the trans and cis isomers of fatty acid and of conjugated linoleic acids are given, and the analyses are described. Papers about the lipids in milks and dairy products from the United States are few; where with the exception of trans-fatty acid isomers and conjugated linoleic acids, almost no research has been reported.