Optimizing fat profiles for nutritional and sensory properties

Current challenge

The opportunity to customize fat content or fatty acid profiles for nutritional benefits is often touted as a potential benefit of alternative meat and seafood (Fraeye et al. 2020). Similarly, the idea of altering fatty acid profiles through dietary interventions has been extensively explored in conventional meat (Burnett et al. 2020). A consumer study on conventional beef indicated that people would pay a premium of USD 1.86/lb for steak enhanced with additional omega-3s and USD 0.79/lb for omega-3-enhanced ground beef (Curran 2015).

While the general idea of improved fatty acid profiles is not unique to alternative meat products, they present advantages regarding the relative ease and simplicity of such manipulations. Animals are complex, multi-organ systems, and meat producers cannot directly manipulate the content of fat depots. Manipulations are especially difficult in ruminants, where dietary lipids are substantially transformed by rumen microbes before they are absorbed (Burnett et al. 2020).

The desirability of higher or lower total fat content or different fatty acid profiles may differ between cuts of meat, and the ability to manipulate fat depots independently would be an advantage (Burnett et al. 2020). While this remains a substantial challenge in conventional meat, it is considerably more tractable in alternative meat (though other challenges related to fat certainly exist, such as the need for encapsulation). Even in cultivated meat and cultivated fat, where the fatty acid profile of the final product depends on both the ingredients in the culture media and the metabolic pathways active in the cells, a reasonably high degree of control seems to be possible through lipid supplementation of the culture media (Yuen et al. 2023).

However, as with conventional meat (Calkins and Hodgen 2007; Burnett et al. 2020), the feasibility of such manipulations may be limited by the effects of the fatty acid profile on the flavor, texture, or color of the final product. Our understanding of the causal relationships between particular types of fat and sensory properties is currently incomplete. Dietary manipulations change conventional meat’s nutrition profile in a complex and often unpredictable manner, especially for ruminants. It is often unclear what chemical changes are most directly responsible for sensory differences. For example, if a given manipulation increases saturated fat content and total fat, it is unclear which change explains any associated changes in palatability. Because the human senses of taste and smell are powerful chemical sensors, foods’ nutritional and sensory properties are inherently linked, and one cannot be optimized without risking unintended consequences for the other. While we know these consequences exist, we need to better understand their magnitude. In other words, to what extent can fat profiles be manipulated without sacrificing on flavor and texture?

Proposed solution

To understand whether and to what extent fat profile manipulations are feasible without sacrificing on flavor, it will be essential to directly and systematically test the effects of fat content and fatty acid profile manipulations on alternative meat palatability. Our current understanding of how the fat content of food affects health outcomes and palatability is somewhat limited, but it provides a useful starting point. Research efforts should focus on manipulations with a high likelihood of beneficial health outcomes while taking into account the existing evidence for or against substantial trade offs in palatability. It is important to note that the concept of “health” is complex and that it is impossible to formulate a universal definition of an optimal fat content or fatty acid profile. Keeping this in mind, below we explore the idea of several nutrition profile manipulations, which the available evidence suggests might be more compatible with healthy diets for many people.

Abbreviations:

SFA: saturated fatty acid

MUFA: monounsaturated fatty acid

PUFA: polyunsaturated fatty acid

Decreased SFA content

The World Health Organization, American Heart Association, and numerous other bodies recommend limiting the consumption of saturated fats to improve cardiovascular health. Alternative meat products in which unsaturated fats replace some of the SFA content could benefit many consumers from a health standpoint.

What is less clear is the impact of decreasing SFA content on the palatability of meat. MUFAs, especially oleic acid, were associated with increased palatability of beef, whereas stearic acid (an SFA) and omega-3 PUFAs were negatively associated with palatability (O’Quinn et al. 2016; Hwang and Joo 2017). However, these results are confounded by the fact that MUFA content (as a percentage of total fat) tends to correlate with the overall fat content in beef (Burnett et al. 2020). In contrast, Hunt et al. (2016) found that SFA and MUFA content (including stearic and oleic acids, respectively) showed little correlation with liking, while the percentage of PUFAs showed a somewhat negative correlation with liking. Despite these inconsistencies, these results indicate the potential to replace some of the SFAs in alternative beef with MUFAs with either positive or neutral impacts on palatability. 

However, because the degree of unsaturation of a given fatty acid determines its melting temperature, the saturated:unsaturated ratio likely can only be altered within a particular window without negatively impacting such products’ cooking properties and acceptability. For example, a study that manipulated the fatty acid profiles of the diets fed to pigs found that fat from those fed a diet high in soybean oil had a PUFA:SFA ratio of 0.74 and a melting temperature of 27.8 °C, while fat from those fed palm kernel oil had a PUFA:SFA ratio of 0.34 and a melting temperature of 32.8 °C (Teye et al. 2006).

Decreased total fat

The effects of reducing dietary fat and replacing it with protein without changing the fatty acid profile are unclear. The American Heart Association recommends reducing saturated fat consumption and replacing it with unsaturated fats to prevent cardiovascular disease (Sacks et al. 2017). However, they concluded that reducing overall dietary fat and replacement mainly with carbohydrates does not prevent coronary heart disease. While it has been suggested that lean meat (~1-4% total fat, depending on species) is preferable to fattier meat when it comes to heart health, this is once again confounded by the fact that the relative percentages of SFAs and PUFAs vary along with total fat content (Li et al. 2005). 

A more substantial problem with the idea that alternative meats could be made “healthier” by reducing total fat is the likely effects on palatability. For U.S. consumers, acceptable levels of intramuscular fat in beef have been estimated to lie between roughly 3 and 7.3% (Miller 2001, as cited by Calkins and Hodgen 2007). This implies that there may be some room for health-focused optimization of fat content (e.g., reducing levels to the lower end of this range), but beyond this, there are likely to be sensory tradeoffs. Taken together, these data suggest that efforts at optimizing alternative meats for effects on health should focus mainly on reducing SFA content rather than lowering the total fat content. As with conventional meat, variety is valuable, as some people will prefer leaner cuts, whether for sensory preference or (real or perceived) health benefits.

Increased PUFAs, including omega-3s

According to the American Heart Association, replacement of dietary SFA with PUFA is “somewhat” more effective than replacement with MUFA at reducing the risk of cardiovascular disease (Sacks et al. 2017). In particular, the highly-unsaturated omega-3 fatty acids have been associated with improved human health outcomes including a lower incidence of cardiovascular disease (Djuricic and Calder 2021). Additionally, the ratio between omega-6 and omega-3 fatty acids is thought to contribute to health outcomes and is higher than optimal for many Western consumers (Simopoulos 2002).

Studies suggest that increased PUFA content, though not increased MUFA content, is associated with increased off-flavors in conventional pork and that increased unsaturated fatty acid content correlates to increased off-flavors in beef (Calkins and Hodgen 2007). Similarly, enhanced omega-3 content led to higher off-flavors in bacon but not pork loin (Calkins and Hodgen 2007). In beef, grass-fed animals tend to have higher overall PUFA levels and lower omega-6:omega-3 ratios (Simopoulos 2002) than grain-fed animals. While most U.S. consumers preferred grain-finished beef, a smaller proportion reported the opposite preference (Calkins and Hodgen 2007). The association between the content of PUFAs, especially omega-3s, and decreased color stability and overall palatability has been well-established and is thought to primarily relate to increased oxidation (Burnett et al. 2020).

However, a study of the quality of pork products from animals fed diets containing palm kernel oil, palm oil, or soybean oil indicated that fatty acid profiles could be substantially changed with minimal impacts on important quality parameters (Teye et al. 2006). The PUFA: SFA ratio differed by ~30% between treatments, but this did not correlate to a significant or substantial difference in flavor liking or overall liking. However, sensory tenderness was slightly but significantly lower in soybean oil-fed animals, as was color saturation. This latter effect may have been due to myoglobin oxidation (Burnett et al. 2020). TBARS values (a measure of oxidation) were higher in soybean oil-fed animals compared to those fed palm kernel or palm oil, though this difference was not significant. Therefore, products with moderately increased PUFA content may be able to fairly easily avoid negative sensory consequences. The extent to which higher levels of PUFA supplementation are feasible without sensory consequences will be a function of how effectively PUFAs can be protected from oxidation.

It will be essential to account for the effects of oxidation on the relationship between PUFA content and flavor in alternative meat and seafood products, especially for those high in omega-3s. Levels of vitamin E, proanthocyanidins, phytic acid, myoglobin, and heme iron have been hypothesized to substantially affect the levels of oxidation in conventional meat (Calkins and Hodgen 2007). While research into the efficacy of antioxidant supplementation in meat remains limited, some studies have shown improved color in beef from cows supplemented with flax or microalgae and antioxidants in comparison to those supplemented with flax or microalgae alone (Burnett et al. 2020) and reduced development of rancid odors in meat from lambs supplemented with rosemary diterpenes (Ortuño et al. 2016). In addition, microencapsulation-based methods (Drusch & Mannino 2009) can protect PUFA-rich oils from exposure to oxygen, and are worthy of further exploration for use in alternative meat products. Therefore, adequate control over oxidation—whether by inclusion of antioxidant compounds in culture media or product formulations or other methods of stabilizing the added PUFAs—may offer the best chance of increasing PUFA content by nutritionally-meaningful amounts without negative impacts on flavor.

Anticipated impact

The idea that fat profiles in meat and seafood might be intentionally modified for health benefits has been explored extensively in the conventional meat industry, but interpreting the results of these studies is difficult. Alternative meat presents an opportunity to better understand the relationship between the content of various classes of fatty acid and palatability because manufacturers have increased control over fat profiles, making the challenge more tractable to address through well-designed experiments. This will allow producers of plant-based and fermentation-derived meat, and to a slightly lesser extent those of cultivated meat, to simultaneously optimize for palatability and nutrition, ultimately resulting in products better matched to the needs of their customers.

A thorough understanding of the effects of fat profiles on flavor and texture will allow alternative meat producers to improve the palatability of their products and reach or exceed taste parity with conventional meat more quickly. Consumer research has identified health as an important factor in purchasing decisions, but a less important factor than taste or familiarity. In other words, people want healthier meat, but they don’t want to sacrifice flavor. Alternative meat products that can make meaningful nutrition claims—such as lower levels of SFAs and higher levels of omega-3s or other PUFAs compared to their conventional equivalents—while tasting as good or better will have a clear leg up in terms of appeal. Ultimately, understanding what is possible when it comes to fat profile optimization will lead to increased market share for alternative meat products—and all the externalized benefits that come along with that—and possibly better health outcomes for consumers.

Related efforts

• Investigation of Versatile Antioxidant Performance in Oil-in-Protein Gel Matrix Environment

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