Addressing flavor challenges in reduced-fat dairy products: A review from the perspective of flavor compounds and their improvement strategies

In recent years, the demand for reduced-fat dairy products (RFDPs) has increased rapidly as the health risks associated with high-fat diets have become increasingly apparent. Unfortunately, lowering the fat content in dairy products would reduce the flavor perception of fat. Fat-derived flavor compounds are the main contributor to appealing flavor among dairy products. However, the contribution of fat-derived flavor compounds remains underappreciated among the flavor improvement factors of RFDPs. Therefore, this review aims to summarize the flavor perception mechanism of fat and the profile of fat-derived flavor compounds in dairy products. Furthermore, the characteristics and influencing factors of flavor compound release are discussed. Based on the role of these flavor compounds, this review analyzed the current and potential flavor improvement strategies for RFDPs, including physical processing, lipolysis, microbial applications, and fat replacement. Overall, promoting the synthesis of milk fat characteristic flavor compounds in RFDPs and aligning the release properties of flavor compounds from the RFDPs with those of equivalent full-fat dairy products are two core strategies to improve the flavor of reduced-fat dairy products. In the future, better modulation of the behavior of flavor compounds by various methods is promising to replicate the flavor properties of fat in RFDPs and meet consumer sensory demands.

Functionality of process cheese made from Cheddar cheese with various rennet levels and high-pressure processing treatments

Due to its versatility and shelf stability, process cheese is gaining interest in many developing countries. The main structural component (base) of most processed cheese formulations is young Cheddar cheese that has high levels of intact casein. Exporting natural Cheddar cheese base from the United States to distant overseas markets would require the aging process to be slowed or reduced. As Cheddar cheese ripens, the original structure is broken down by proteolysis and solubilization of insoluble calcium phosphate. We explored the effect of varying rennet levels (we also used a less proteolytic rennet) and application of high-pressure processing (HPP) to Cheddar cheese, as we hoped these treatments might limit proteolysis and concomitant loss of intact casein. To try to retain high levels of insoluble Ca, all experimental cheeses were made with a high-draining pH and from concentrated milk. To compare our intact casein results with current practices, we manufactured a Cheddar cheese that was prepared according to typical industry methods (i.e., use of unconcentrated milk, calf chymosin [higher levels], and low draining pH value [∼6.2]). All experimental cheeses were made from ultrafiltered milk with protein and casein contents of ∼5.15% and 4.30%, respectively. Three (low) rennet levels were used: control (38 international milk clotting units/mL of rennet per 250 kg of milk), and 25% and 50% reduced from this level. All experimental cheeses had similar moisture contents (∼37%) and total Ca levels. Four days after cheese was made, half of the experimental samples from each vat underwent HPP at 600 MPa for 3 min. Cheddar cheese functionality was monitored during aging for 240 d at 4°C. Cheddar cheese base was used to prepare process cheese after aging for 14, 60, 120, 180, and 240 d. Loss tangent (LT) values of cheese during heating were measured by small strain oscillatory rheology. Intact casein levels were measured using the Kjeldahl method. Acid or base titrations were used to determine the buffering capacity and insoluble Ca levels as a percentage of total Ca. The LTmax values (an index of meltability) in process cheese increased with aging for all the cheese bases; the HPP treatment significantly decreased LTmax values of both base (natural) and process cheeses. All experimental cheeses had much higher levels of intact casein compared with typical industry-make samples. Process cheese made from the experimental treatments had visually higher stretching properties than process cheese made from Cheddar with the typical industry-make procedure. Residual rennet activity was not affected by rennet level, but the rate of proteolysis was slightly slower with lower rennet levels. The HPP treatment of Cheddar cheese reduced residual rennet activity and decreased the reduction of intact casein levels. The HPP treatment of Cheddar cheese resulted in process cheeses that had slightly higher hardness values, lower LTmax values, and retained higher storage modulus values at 70°C. We also observed that the other make procedures we used in all experimental treatments (i.e., using a less proteolytic chymosin, using a concentrated cheese milk, and maintaining a high draining pH value) had a major effect on retaining high levels of intact casein.

Effects of fat content on the textural and in vivo buccal breakdown properties of soy yogurt

This study aimed to evaluate the effects of fat content on the textural and in vivo buccal breakdown properties of soy yogurt (SY) at different pH (5.4, 5.0, and 4.6). The microbial analysis, textural and rheological properties, and interfacial protein composition of all the samples were monitored. Microbial results suggested that the increased fat content in SY-5.0 and SY-4.6 resulted in significantly high viable cell counts of lactic acid bacteria (LAB). Textural studies demonstrated that the presence of a low fat content (1-3%) significantly reduced the hardness, springiness, and gumminess of the sample, but this effect was negligible with the addition of fat content (4-5%). The apparent viscosity and thixotropy of the SY-4.6 sample increased as the fat content increased. in vivo buccal digestion showed that a high fat content (2-4%) reduced the number of chews and chewing durations, which might be correlated with high oil droplet release (%) after mastication.

A 100-Year Review: Cheese production and quality

In the beginning, cheese making in the United States was all art, but embracing science and technology was necessary to make progress in producing a higher quality cheese. Traditional cheese making could not keep up with the demand for cheese, and the development of the factory system was necessary. Cheese quality suffered because of poor-quality milk, but 3 major innovations changed that: refrigeration, commercial starters, and the use of pasteurized milk for cheese making. Although by all accounts cold storage improved cheese quality, it was the improvement of milk quality, pasteurization of milk, and the use of reliable cultures for fermentation that had the biggest effect. Together with use of purified commercial cultures, pasteurization enabled cheese production to be conducted on a fixed time schedule. Fundamental research on the genetics of starter bacteria greatly increased the reliability of fermentation, which in turn made automation feasible. Demand for functionality, machinability, application in baking, and more emphasis on nutritional aspects (low fat and low sodium) of cheese took us back to the fundamental principles of cheese making and resulted in renewed vigor for scientific investigations into the chemical, microbiological, and enzymatic changes that occur during cheese making and ripening. As milk production increased, cheese factories needed to become more efficient. Membrane concentration and separation of milk offered a solution and greatly enhanced plant capacity. Full implementation of membrane processing and use of its full potential have yet to be achieved. Implementation of new technologies, the science of cheese making, and the development of further advances will require highly trained personnel at both the academic and industrial levels. This will be a great challenge to address and overcome.