Acceleration Of Cheese Ripening Research Articles

Preparation of pH-responsive chitosan microspheres containing aminopeptidase and their application in accelerating cheese ripening

Microencapsulated enzymes have been found to effectively accelerate cheese ripening. However, microencapsulated enzyme release is difficult to control, often resulting in enzyme release during cheese processing and causing texture and flavor defects. This study aims to address this issue by developing aminopeptidase-loaded pH-responsive chitosan microspheres (A-CM) for precise enzyme release during cheese ripening. An aminopeptidase with an isoelectric point (pH 5.4) close to the pH value of cheese ripening was loaded on chitosan microspheres through electrostatic interaction. Turbidity titration measurements revealed that pH 6.5 was optimal for binding aminopeptidase and microspheres, affording the highest loading efficiency of 58.16%. Various characterization techniques, including scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy confirmed the successful loading of aminopeptidase molecules on the chitosan microspheres. In vitro release experiments conducted during simulated cheese production demonstrated that aminopeptidase release from A-CM was pH responsive. The microspheres retained the enzyme during the coagulation and cheddaring processes (pH 5.5-6.5) and only released it after entering the cheese-ripening stage (pH 5.0-5.5). By loading aminopeptidase on chitosan microspheres, the loss rate of the enzyme in cheese whey was reduced by approximately 79%. Furthermore, compared with cheese without aminopeptidase and cheese with aminopeptidase added directly, the cheeses made with A-CM exhibited the highest proteolysis level and received superior sensory ratings for taste and smell. The content of key aroma substances, such as 2/3-methylbutanal and ethyl butyrate, in cheese with A-CM was more than 15 times higher than the others. This study provides an approach for accelerating cheese ripening through the use of microencapsulated enzymes.

Metatranscriptomic Analyses Unravel Dynamic Changes in the Microbial and Metabolic Transcriptional Profiles in Artisanal Austrian Hard-Cheeses During Ripening.

Vorarlberger Bergkäse (VB) is an artisanal Austrian washed-rind hard cheese produced from alpine cows’ raw milk without the addition of ripening cultures. Ripening time is a key factor in VB, as it strongly influences the microbial communities present in the cheeses and the organoleptic properties of the product. In this study, the microbial and metabolic transcriptional profiles in VB rinds at different ripening times were investigated. VB products before (30 days of ripening) and after (90 days of ripening) selling were selected, RNA was extracted and subjected to shotgun metatranscriptomic sequencing. The analysis revealed some of the previously described abundant bacterial taxa of Brevibacterium, Corynebacterium, Halomonas, Psychrobacter, and Staphylococcus to be highly active in VB rinds. Additionally, the investigation of most important metabolic pathways in cheese ripening clearly showed differences in the gene transcription profiles and the active microbiota between the two ripening points investigated. At 30 days of ripening, metabolic events related with the degradation of residual lactose, lactate, citrate, proteolysis, and lipolysis were significantly more transcribed and mainly associated with Staphylococcus. On the other hand, genes involved in the degradation of smaller compounds derived from previous metabolism (i.e., metabolism of free amino acids and fatty acids) were significantly more expressed in VB rinds with 90 of ripening, and mainly associated with Brevibacterium and Corynebacterium. These latter metabolic activities are responsible of the generation of compounds, such as methanethiol and 2,3-butanediol, that are very important for the flavor and aroma characteristics of cheeses. This study shows the dynamic changes in the gene transcriptional profiles associated with energy substrates metabolism and the generation of organoleptic compounds during VB ripening and uncovers bacterial taxa as key drivers of the ripening process. These taxa might be the target for future studies toward an accelerated cheese ripening and the enhancement of its organoleptic properties.

Optimization of Microbial Rennet Encapsulation in Alginate – Chitosan Nanoparticles

The milk-coagulating enzyme, rennet, is widely used in cheese making. Recently stabilization of rennet, especially in accelerated cheese ripening, has received considerable interest. As we know encapsulation is one of the enzyme immobilization methods, which could increase enzyme stability. In this study, the effects of alginate, chitosan and, CaCl2 on rennet encapsulation were evaluated and optimized using RSM. Under the optimal conditions alginate, chitosan, and CaCl2 were 0.04%, 0.1%, and 0.1% respectively. At the optimum point, encapsulation efficiency, particle size, and zeta potential were evaluated to be 61.8%, 323 nm, and 25 mV, respectively. The effect of temperature and pH on the enzyme activity was evaluated, and the results showed that encapsulated enzyme had higher activity at various pH and temperature in comparison with the free enzyme. Also, the enzyme release data in all pH values were fitted to Korsmeyer-Peppas model and the n exponent indicated that the release mechanism was Fickian. The electrostatic interactions between enzyme, alginate, and chitosan were confirmed by infrared spectroscopy. No statistical difference was found between the Km and Vmax of encapsulated and free enzymes.

The multifunctional activity of water‐soluble peptides’ extract of Domiati cheese during accelerated ripening by Neutrase

This study aimed to through light on the functionality of water-soluble peptide extract (WSPE) of Domiati cheese as affected by Neutrase (2.5 and 5 mg/L milk) in addition to rennin to accelerate cheese ripening. Antioxidant, angiotensin-converting enzyme (ACE) inhibitory, and anticancer activities of WSPE during ripening were assessed. All parameters under study showed a significant increase during ripening in a dose-dependent manner. WSPE from fresh or ripened cheese exhibited antioxidant, ACE inhibitory, and anticancer activities as a consequence of many bioactive peptides present. These bioactive peptides were mainly originated from α-, β-, and κ - casein. The activities of WSPE were directly proportional to the dose of the Neutrase used for cheese ripening. Practical applications Domiati cheese is the most popular and most consumable Egyptian soft cheese whether it is fresh or ripened. Cheese ripening acquires the desirable sensory properties as a result of the enzymatic degradation of its components, that is, fat and protein and as a result the release of bioactive peptides which exhibit special functions may influence consumer health. There is a wide variety of physiological activities induced by bioactive peptides. The functions of those peptides differ according to the enzyme used in manufacturing and for accelerating the ripening process. Due to the lack of information about the bioactive peptides in Domiati cheese, Neutrase was used in the manufacture of Domiati cheese to accelerate its ripening and produce a new type of Domiati cheese with high biological and functional properties and thus increasing the consumer health awareness.

Effect of elevated temperature on the microstructure of full fat Cheddar cheese during ripening

Elevated temperatures have been widely studied as a route to accelerate cheese ripening and decrease energy and storage requirements but the impact of temperature on the underlying microstructure of the cheese during prolonged periods of ripening is poorly understood. In this study, Cheddar cheese was matured at four different ripening temperatures (8 °C, 15 °C, 20 °C or a combination of 8 °C and 15 °C) and the impact on cheese microstructure assessed using confocal laser scanning microscopy, cryo scanning electron microscopy and quantitative image analysis of 3D images. An increase in ripening temperature was shown to alter the microstructure of the cheese protein network after only a few weeks of ripening. Incubation at 20 °C significantly reduced branching within the protein network, leading to thicker protein strands and larger pores after 33 days. These structural changes coincided with increased proteolysis, consistent with solubilisation of the protein network; they also led to a softer, less chewy and less cohesive cheese. While the concentration of biogenic amines tryptamine and tyramine were observed to increase with ripening temperature, the concentrations were generally low, confirming that biogenic amines do not represent a health concern under the conditions examined. This study illustrates how 3D image analysis can be used to observe and quantify the effect of process changes on cheese structure, assisting our understanding of the link between structure and function in Cheddar cheese.

Response Surface Methodology Modelling of an Aqueous Two-Phase System for Purification of Protease from Penicillium candidum (PCA 1/TT031) under Solid State Fermentation and Its Biochemical Characterization.

Penicillium candidum (PCA 1/TT031) synthesizes different types of extracellular proteases. The objective of this study is to optimize polyethylene glycol (PEG)/citrate based on an aqueous two-phase system (ATPS) and Response Surface Methodology (RSM) to purify protease from Penicillium candidum (PCA 1/TT031). The effects of different PEG molecular weights (1500–10,000 g/mol), PEG concentration (9%–20%), concentrations of NaCl (0%–10%) and the citrate buffer (8%–16%) on protease were also studied. The best protease purification could be achieved under the conditions of 9.0% (w/w) PEG 8000, 5.2% NaCl, and 15.9% sodium citrate concentration, which resulted in a one-sided protease partitioning for the bottom phase with a partition coefficient of 0.2, a 6.8-fold protease purification factor, and a yield of 93%. The response surface models displayed a significant (p ≤ 0.05) response which was fit for the variables that were studied as well as a high coefficient of determination (R2). Similarly, the predicted and observed values displayed no significant (p > 0.05) differences. In addition, our enzyme characterization study revealed that Penicillium candidum (PCA 1/TT031) produced a slight neutral protease with a molecular weight between 100 and 140 kDa. The optimal activity of the purified enzyme occurred at a pH of 6.0 and at a temperature of 50 °C. The stability between different pH and temperature ranges along with the effect of chemical metal ions and inhibitors were also studied. Our results reveal that the purified enzyme could be used in the dairy industry such as in accelerated cheese ripening.

Isolation and characterization of Lactobacillus helveticus DSM 20075 variants with improved autolytic capacity

Lactobacillus helveticus is widely used in dairy fermentations and produces a range of enzymes, which upon cell lysis can be released into the cheese matrix and impact degradation of proteins, peptides and lipids. In our study we set out to explore the potential of Lb. helveticus DSM 20075 for increased autolytic capacity triggered by conditions such as low pH and high salt concentrations encountered in cheese environments. Lb. helveticus DSM 20075 was subjected to varied incubation temperatures (ranging from 37 to 50°C). High-temperature incubation (in the range of 45 to 50°C) allowed us to obtain a collection of six variant strains (V45-V50), which in comparison to the wild-type strain, showed higher growth rates at elevated temperatures (42°C–45°C). Moreover, variant strain V50 showed a 4-fold higher, in comparison to wild type, autolytic capacity in cheese-like conditions. Next, strain V50 was used as an adjunct in lab-scale cheese making trials to measure its impact on aroma formation during ripening. Specifically, in cheeses made with strain V50, the relative abundance of benzaldehyde increased 3-fold compared to cheeses made with the wild-type strain. Analysis of the genome sequence of strain V50 revealed multiple mutations in comparison to the wild-type strain DSM 20075 including a mutation found in a gene coding for a metal ion transporter, which can potentially be linked to intracellular accumulation of Mn2+ and benzaldehyde formation. The approach of high-temperature incubation can be applied in dairy industry for the selection of (adjunct) cultures targeted at accelerated cheese ripening and aroma formation.

Identification and functional characterization of AclB, a novel cell-separating enzyme from Lactobacillus casei

Autolysis of nonstarter lactic acid bacteria (NSLAB) was favorable for the development of flavor compounds during cheese manufacture. Among these bacteria, Lb. casei was regarded as the most important microbiota involved in cheese processes. In this study, a novel autolysin named AclB was identified in the genome of Lb. casei BL23 and its modular structure was predicted through bioinformatic approaches. Subsequently, its transcription profile in the exponential phase, hydrolytic activities against cell walls, enzymatic properties under different conditions, physiological function via gene inactivation and upregulation assays, as well as potential applications to NSLAB's autolysis were fully investigated. According to the results, AclB was recognized as a species-specific cell-separating enzyme, responsible for cell separation after cell division in Lb. casei BL23. The purified AclB showed considerable hydrolyzing activities towards cell walls, indicating its enzymatic nature as peptidoglycan hydrolase, or autolysin. The highest activity of AclB was determined at pH5.0 and 37°C, and the expression vector constructed based on AclB was shown to facilitate the controlled lysis of Lb. casei BL23 hosts. In summary, this study provided insight into the enzymatic properties of a novel autolysin involved in cell separation of Lb. casei BL23, which is promising to accelerate cheese ripening and improve cheese quality.

Applications of nanoliposomes in cheese technology

Among microencapsulation techniques used in food production, nanoliposomes are known to be one of the most interesting methods for the encapsulation of flavours, essential oils, amino acids, vitamins, minerals, enzymes, micro‐organisms, redox agents, colourants, antioxidants and antimicrobials. Research has also been conducted on possible applications of nanoliposomes in cheese production by the encapsulation of ferrous glycinate, ferrous sulphate, antioxidants, nisin, β‐galactosidase and cheese‐ripening enzymes. In this article, nanoliposome application in cheese production has been reviewed under three main themes, namely (i) acceleration of cheese ripening, (ii) fortification of cheese with vitamins and minerals and (iii) increasing shelf life of cheese products. Various aspects of nanoliposome application in cheese technology including currently available preparation methods, efficiency of nanoliposomal enzymes, their effects on the acceleration of cheese ripening as well as rheological and chemical properties of the cheese curd are discussed.

The mathematical modelling of cheese ripening

A mathematical model is developed for the ripening of cheese. Such models may assist predicting final cheese quality using measured initial composition. The main constituent chemical reactions are described with ordinary differential equations. Numerical solutions to the model equations are found using Matlab. Unknown parameter values have been fitted using experimental data available in the literature. The results from the numerical fitting are in good agreement with the data. Statistical analysis is performed on near infrared data provided to the MISG. However, due to the inhomogeneity and limited nature of the data, not many conclusions can be drawn from the analysis. A simple model of the potential changes in acidity of cheese is also considered. The results from this model are consistent with cheese manufacturing knowledge, in that the pH of cheddar cheese does not significantly change during ripening. References D. Dawson and J. Feagan, Bacteriology of cheddar cheese: A study of starter organisms in manufacture and maturing. J. Dairy Res. 24 , 210–224, 1957. M.A. Drake, R.E. Miracle and D.J. McMahon, Impact of fat reduction on flavor and flavor chemistry of Cheddar cheeses. Journal of Dairy Science 93 , 5069–5081, 2010. M. Fenelon and T. Guinee, Primary proteolysis and textural changes during ripening in cheddar cheeses manufactured to different fat contents. Int. Dairy J. 10 , 151–158, 2000. R. Hutkins and N. Nannen, pH homeostasis in lactic acid bacteria. J. Dairy Sci. 76 , 2354–2365, 1992. M. Johnson, Cheese pH–-what's behind the rise and fall? Technical Report 14, Wisconsin Center for Dairy Research, December 2002. J.K. Kim, K. Starzak, G.W. Preckshot, R. Marshall and R.K. Bajpai, Critical reactions in ripening of cheeses–-a kinetic analysis. Appl. Biochem. Biotech. 45 , 51–68, 1994. B.A. Law and A.S. Wigmore, Microbial proteinases as agents for accelerated cheese ripening. Int. J. Dairy Tech. 35 , 75–76, 2007. R. Lawrence, L. Creamer, and J. Gilles, Texture development during cheese ripening. J. Dairy Sci. 70 , 1748–1760, 1987. R. Marsili, Monitoring chemical changes in cheddar cheese during aging by high performance liquid chromatography and gas chromatography techniques. Journal of Dairy Science 68 , 3155–3161, 1985. K. Presser, D. Ratkowsky, and T. Ross, Modelling the growth rate of Escherichia coli as a function of pH and lactic acid concentration. Appl. Environ. Microbiol. 63 , 2355–2360, 1997. S. Rehman, D. Waldron, and P. Fox, Effect of modifying lactose concentration in cheese curd on proteolysis and in quality of Cheddar cheese. Int. Dairy J. 14 , 591–597, 2004. T. Singh, M. Drake, and K. Cadwallader, Flavour of cheddar cheese: A chemical and sensory perspective. Compr. Rev. Food Sci. F. 2 , 166–189, 2003. S. Toelstede and T. Hofmann, Kokumi-active glutamyl peptides in cheeses and their biogeneration by Penicillium roquefortii. Agric. Food Chem. 13 , 3738–3748, 2009.

Recent patents on microbial proteases for the dairy industry.

This paper reviews the general characteristics of exo and endopeptidases of microbial origin currently used in the milk industry. It also includes recent patents developed either to potentiate the enzymatic activity or to improve the resulting milk derivatives. The main application of these proteases is in the cheese-making industry. Although this industry preferentially uses animal rennets, and in particular genetically engineered chymosins, it also utilizes milk coagulants of microbial origin. Enzymes derived from Rhizomucor miehei, Rhizomucor pusillus and Cryphonectria parasitica are currently used to replace the conventional milk-clotting enzymes. In addition, the dairy industry uses microbial endo and exoproteases for relatively new applications, such as debittering and flavor generation in cheese, accelerated cheese ripening, manufacture of protein hydrolysates with improved functional properties, and production of enzyme-modified cheeses. Lactic acid bacteria play an essential role in these processes, hence these bacteria and the proteases they produce are currently being investigated by the dairy industry and are the subject of many of their patent applications.

Comparation of the Flavor of Different Cheese Flavouring Agents Produced by Using Surface Ripening Bacterium and/or Enzymes

To accelerate cheese ripening, enhance its flavor types and intensity and make cheese flavoring agent in shorter time, surface ripening bacterium (<em>Brevibacterium linens</em> and <em>Debaryomyces hansenii</em>) and/or enzymes (<em>Flavorzyme</em> 500 MG and <em>Palatase</em> 20000 L) were used in cheese curd. In this study, aroma compounds generated by using ripening cultures and/or enzymes were analyzed. The control l was made by inoculating ripening cultures, while the control 2 was made through enzymes-modified only. Results showed that cheese flavoring agent made by using ripening strains in combination with enzymes had more volatile flavor compounds (at least 44) than that used just ripening bacterium (26) or just two enzymes (27). Then, through Solid-phase microextraction and Gas Chromatography-Mass Spectrometry analysis, we knew that sample 1, which was made through proteolysis first, next sprayed ripening cultures and last lipolysis, generated 54 flavor compounds. Sample 2, which enzymed cheese curd first, then incubated ripening cultures, had 44 aroma compounds. However, the controls 1, incubated ripening strains only, had 26 volatile compounds, while the control 2, enzymed only, had 27 volatile compounds. This study reveals that ripening bacterium could contribute more to the generation of acids, sulphur compounds, miscellaneous compounds and alcohols, it has a good potential to be used in cheese flavoring agents making. Besides, the combination of surface strains and enzymes, especially using Flavorzyme 500 MG first, then sprayed ripening cultures and at last Palatase 20000 L, could get more volatile compounds.

Construction and Potential Application of Controlled Autolytic Systems for Lactobacillus casei in Cheese Manufacture

The rapid release of intracellular enzymes into the curd by the autolysis of lactic acid bacteria starters is universally recognized as a critical biological process to accelerate cheese ripening. Lactobacillus casei is typically the dominant nonstarter lactic acid bacterium in the ripening cheese. In this study, two controlled autolytic systems were established in L. casei BL23, based on the exploitation of the autolysins sourced from Lactococcus lactis (AcmA) and Enterococcus faecalis (AtlA). The lysis abilities of the systems were demonstrated both in broth and a model cheese, in which a fivefold increase in lactate dehydrogenase activity was detected in the curd with sufficient viable starter cells being maintained, indicating that they could lead to the timely release of intracellular enzymes.

Influence of Adjuncts as Debittering Aids on the Sensory and Biochemical Properties of Enzyme Modified Cheese-Base

An attempt has been made to accelerate the flavour development in cheese slurry with the help of exogenous proteolytic and lipolytic enzymes (1:1 proportion, each at the rate of 0.025 % by weight of cheese-base) and ripening at elevated temperatures (i.e. 20 ± 1 °C) for up to 12 days. Bitterness, the necessary consequence of accelerated cheese ripening, has been the main objective of the present investigation. Adjunct cultures Lactobacillus casei and Lactobacillus helveticus were used as debittering aids. The debittering activity was monitored using electrophoretic pattern and sensory evaluation of the product. Freeze-shocked adjunct Lactobacillus helveticus produced enzyme-modified cheese slurry with no detectable bitterness. The usage of adjunct cultures either viable or attenuated, ripening period and interactions amongst these parameters had significant (P < 0.05) influence on all of the sensory characteristics monitored.

Measuring and Improving Eco-efficiency Using Data Envelopment Analysis

Summary The concept of eco-efficiency can be defined with the “product value/environmental influence” ratio. Different models have been proposed to measure eco-efficiency. The main difference among them is the weighting system used to aggregate the environmental results. Data envelopment analysis (DEA) permits this aggregation without requiring a subjective judgment about the weights. In this study, we applied a DEA model to Spanish Mah´ on-Menorca cheese production to determine the most eco-efficient production techniques. To this end, 16 scenarios of Mah´ on-Menorca cheese production were built regarding technical (degree of automation) and cleaner production criteria. The environmental impacts were assessed by means of life cycle assessment. We carried out an economic assessment by determining the economic value added and the net income for each scenario. The results are referred to as 1 kilogram (kg) cheese ripened over 105 days. Through DEA, an eco-efficiency ratio between 0 and 1 was obtained. Three scenarios were found to be ecoefficient, with a high degree of automation (enclosed vat and molding and demolding machines) and accelerated cheese ripening.

Determinação da compatibilidade de desenvolvimento de culturas bacteriocinogênicas e fermento láctico

Além da utilização como bioconservantes de alimentos, algumas culturas bacteriocinogênicas estão sendo empregadas para acelerar a maturação de queijos. Porém a compatibilidade de desenvolvimento destas culturas com o fermento láctico é essencial para a obtenção de produtos característicos. O objetivo deste estudo foi avaliar a compatibilidade de desenvolvimento de Lactococcus lactis subsp. lactis ATCC 11454, Lactobacillus plantarum ALC 01 e Enterococcus faecium FAIR-E 198 com duas marcas comerciais de fermentos lácticos. Inicialmente, foi determinada a sensibilidade in vitro dos fermentos às culturas bacteriocinogênicas, somente Lc. lactis subsp. lactis ATCC 11454 foi capaz de promover a inibição de ambos os fermentos. Durante desenvolvimento associativo em leite a 35 ºC, as culturas bacteriocinogênicas não afetaram significativamente a produção de ácido láctico pelos fermentos. Estes, por sua vez proporcionaram aumento significativo da atividade de pediocina AcH e enterocina FAIR-E 198 e supressão da atividade da nisina. Dentre todas as culturas lácticas, Lb. plantarum ALC 01 apresentou a maior atividade de aminopeptidases (0,226 a 0,390). Portanto, baseado nos resultados em questão, Lb. plantarum ALC 01 e E. faecium FAIR-E 198 apresentam características de compatibilidade de desenvolvimento com o fermento mesofílico tipo O para serem empregadas como adjuntas no processamento de queijos.

THE EFFECT OF ADJUNCT CULTURES ON SOME CHEMICAL AND BIOCHEMICAL PROPERTIES OF WHITE-BRINED CHEESE

ABSTRACT The influence of different adjunct cultures on some of the chemical and biochemical properties of white-brined cheese was investigated. Four batches of cheese were produced: C, with no added adjuncts, containing only cheese culture (Lactococcus lactis ssp. lactis plus Lc. lactis ssp. cremoris); CY, containing C culture plus yogurt culture (Streptococcus thermophilus + Lb. delbrueckii ssp. bulgaricus); CH, containing C culture plus Lactobacillus helveticus; and CYH, containing all of them. Analyses were carried out on days 2, 30, 60 and 90 of ripening. It was found that the addition of different adjunct starters to the cheese influenced (P < 0.01) the chemical composition significantly, except salt contents (P > 0.05). Total solids, protein, fat and pH values were higher in C cheese than the others. On the other hand, titratable acidity of C and CY cheeses was lower than that of CH and CYH cheeses. Although the lipolysis (acid degree value), water-soluble nitrogen (WSN) and trichloroacetic acid-soluble nitrogen (TCA-SN) values of cheeses were affected significantly (P < 0.01) from these treatments, no significant differences exist (P > 0.05) among phosphotungstic acid-soluble nitrogen values. Cheeses made with CYH culture had the highest lipolysis, WSN and TCA-SN. Degradation rates of αs1- and β-casein were higher in CYH cheese followed by CY, CH and C cheeses. Also, breakdown products of casein were higher in CY, CH and CYH cheeses compared with the control cheese. The amounts ofαs1- and β-caseins of all cheese samples decreased continuously during the ripening period, while the amounts of αs1-I casein and other breakdown products increased. PRACTICAL APPLICATIONS Starter cultures contribute to cheese sensory quality with their peptidase activity. In artisanal cheese production, the cheese is made without the deliberate addition of a starter culture relying on the indigenous flora of the milk for ripening. Recently, mesophilic and/or thermophilic starter cultures were used in the manufacture of Turkish white-brined cheese. Little information on using adjunct culture in white cheese has been reported and may provide information to improve the process and ripening by enhancing the quality of the final product while preserving its typical nature. Adjunct cultures can accelerate flavor development or contribute additional flavors to cheese as it ages and control bitterness in aged cheeses, depending on the fermentation process and adjunct type. They can also accelerate cheese ripening, which may allow substantial cost savings for the cheese industry.

Flavour precursor development in Cheddar cheese due to lactococcal starters and the presence and lysis of Lactobacillus helveticus.

The rapid release of intracellular enzymes due to autolysis of lactic acid bacteria in the cheese matrix has been shown to accelerate cheese ripening. The objective of this work was to investigate the evolution of the flavour precursors, individual free amino acids (FAAs), free fatty acids (FFAs) and volatile compounds that contribute to the sensory profiles of cheeses at 2, 6 and 8 months of ripening in Cheddar cheese manufactured using starter systems which varied with respect to their autolytic properties. Starter system A contained a blend of two commercial Lactococcus lactis strains (223 and 227) which had a low level of autolysis. System B was identical to A but also included a highly autolytic strain of Lactobacillus helveticus (DPC4571). System C contained only strain DPC4571. Levels of all individual FAAs were elevated in cheeses B and C relative to A after 2 months of ripening. By 8 months of ripening the main FAA were glutamate, leucine, lysine, serine, proline and valine. Levels of C 6:0, C 8:0, C 12:0 and C 18:0 fatty acids did not vary greatly over ripening, while levels of C 4:0, C 10:0, C 14:0, C 16:0 and C 18:1 were elevated in cheeses B and C. Principal component analysis of the headspace volatiles separated cheese A from cheeses B and C. Cheeses B and C had highest levels of dimethyl disulphide, carbon sulphide, heptanal, dimethyl sulphide, ethyl butanoate, 2-butanone, and 2-methyl butanal and were described as having a ‘caramel’ odour and ‘sweet’, ‘acidic’ and ‘musty’ flavour. Cheese A had highest levels of 2-butanol, 2-pentanone, 2-heptanone, 1-hexanol and heptanal and was described as having a ‘sweaty/ sour’ odour and ‘soapy’, ‘bitter’ and ‘mouldy’ flavour. The results highlight the impact of starter lactococci on flavour precursor development and the positive effect of Lb. helveticus and the lysis of this strain on enhancing levels of substrate and flavour precursors early during ripening resulting in early flavour development.

Microencapsulation of enzymes for potential application in acceleration of cheese ripening

An encapsulation efficiency of 70% was achieved when flavourzyme was encapsulated in selected polymers and gelled in 0.1 m CaCl 2 containing 0.1% (w/v) chitosan. Enzyme retention in capsules did not increase with alginate concentration or with coating of capsules with 0.15% (w/v) alginate or 0.05% (w/v) poly l-lysine. Gelling duration of 10 min was found to be optimum, while 2.0% trisodium citrate was necessary for efficient release of encapsulated flavourzyme. During 10-week storage after freeze-drying and freezing, about 80% retention of enzyme activity was noted in flavourzyme capsules with or without poly l-lysine coating, while air-dried capsules retained about 53% activity and 32% on coating with poly l-lysine over 10 weeks. Flavourzyme leakage from capsules increased with an increase in the duration of the simulated cheese press from 4 to 16 h. Capsule addition before rennetting resulted in an even distribution compared with capsule addition before salting.

Biotechnological Methods to Accelerate Cheddar Cheese Ripening

ABSTRACTCheese is one of the dairy products that can result from the enzymatic coagulation of milk. The basic steps of the transformation of milk into cheese are coagulation, draining, and ripening. Ripening is the complex process required for the development of a cheese's flavor, texture and aroma. Proteolysis, lipolysis and glycolysis are the three main biochemical reactions that are responsible for the basic changes during the maturation period. As ripening is a relatively expensive process for the cheese industry, reducing maturation time without destroying the quality of the ripened cheese has economic and technological benefits. Elevated ripening temperatures, addition of enzymes, addition of cheese slurry, attenuated starters, adjunct cultures, genetically engineered starters and recombinant enzymes and microencapsulation of ripening enzymes are traditional and modern methods used to accelerate cheese ripening. In this context, an up to date review of Cheddar cheese ripening is presented.