Oral processing of bread: Implications of designing healthier bread products

The eating rate of bread predicted from its sensory texture and physical properties

Eating rate (ER) can moderate energy intake and ER can be modified by the texture and physical properties of food. However, the magnitude of the effects is not well known. The aim of this study was to investigate how bread texture and physical properties determine ER. In a randomised crossover study, 36 healthy participants (age: 25 ± 6 years, BMI: 22 ± 2 kg m-2) consumed nine different bread types. Video coding was used to characterise oral processing behaviour. Sensory texture was evaluated on visual analogue scales. Physical properties were measured using texture profile analysis, puncture tests, geometrical and water-related measures. Two models were developed using response surface methodology (RSM) that predict the ER based on sensory and physical properties. The results showed from slow to fast ER: bread slices < hard buns < soft buns. The slowest bread type (wholemeal bread slice) was consumed 40% slower than the fastest bread type (soft white bun) (P < 0.001), explained by smaller bite sizes and more chews. For the sensory texture, ER was positively correlated with crumb adhesiveness and negatively correlated with crumb dryness. For the physical properties, ER was positively correlated with height and volume, and negatively with crumb cohesiveness and crust hardness. The models based on physical properties (R2 = 0.91) and sensory texture (R2 = 0.89) were both able to estimate ER, but the model based on physical properties performed slightly better. The insights from the relationships from the sensory and physical measures can both be used to modify the texture of breads, to effectively decrease ER and eventually help to prevent overconsumption.

The combined effect of gluten addition and semolina cell wall integrity reduces the oral sugar release and the insulinemic response to bread in healthy volunteers

PURPOSE

A strategy to reduce starch digestibility is to limit its accessibility to α-amylase by preserving the integrity of cells where starch is encapsulated. Coarse flour is rich in intact cells and can be used for this purpose. However, making bread with coarse flour negatively affects crumb cohesiveness, which may increase the gastric disintegration rate, and enhance starch accessibility. Therefore, this study aimed to assess the combined effect of coarse semolina and its 20% gluten substitution in bread in healthy volunteers on glycemic and insulinemic responses, oral processing and bolus characteristics.

METHODS

Apparently, healthy volunteers (n = 16) randomly consumed bread made with coarse semolina and 20% gluten substitution (80CS_20G), its counterpart with fine semolina (80FS_20G), and bread with fine semolina and 5% gluten (95FS_5G). The glycemic and insulinemic responses were measured over 2 h after bread consumption. Mastication behaviour, bolus properties and reducing sugar were also evaluated.

RESULTS

No differences in glycemic responses and mastication were observed among the samples. 80CS_20G and 80FS_20G exhibited similar textural properties but 80CS_20G released less reducing sugars and elicited a lower insulin response at 30 min than 80FS_20G, probably due to intact cells that limit starch accessibility. Also, 95FS_5G released lower reducing sugars and had lower insulin peak than 80FS_20G. The compact structure of 95FS_5G may have delayed starch hydrolysis by restricting α-amylase accessibility.

CONCLUSION

Combining gluten and coarse semolina resulted in bread with a lower release of reducing sugars, a reduced insulinemic peak and textural properties similar to the counterpart with fine semolina.

CLINICAL TRIAL REGISTRATION NUMBER

The trial is registered at ClinicalTrials.gov: NCT06152874.

Visualization of Moisture Content, Reducing Sugars, and Chewiness in Bread During Oral Processing Based on Hyperspectral Imaging Technology

This study evaluated the differences in oral processing and texture perception of breads with varying compositions. The research investigated the dynamic changes in moisture content (MC), reducing sugars (RSs), and chewiness of the bolus formed from white bread (B0) and 50% whole-wheat bread (B50) during oral processing. Hyperspectral imaging (HSI) combined with chemometric methods was used to establish quantitative prediction models for MC, RSs, and chewiness, and to create visual distribution maps of these parameters. The results showed that B0 had a higher moisture content and a faster hydration rate than B50 during the initial stages of oral processing, indicating greater hydrophilicity and ease of saliva wetting. Additionally, the uniformity of moisture distribution in the bolus of B0 was higher than that of B50. B50 exhibited significantly lower RSs content and poorer distribution uniformity compared to B0. The primary differences in chewiness between the two types of bread were observed during the early stages of oral processing, with B50 requiring more chewing effort initially. This study demonstrated that HSI technology can effectively monitor and elucidate the compositional changes in food particles during oral processing, providing new insights into bread texture perception and offering a scientific basis for improving bread processing and texture.

Oral processing of bakery products: An overview of current status and future outlook

Food oral processing (FOP) is an emerging research topic that allows a better comprehension of the relation between intrinsic food factors (physicochemical and sensory properties), and human physiology and eating behaviours. FOP can then help in the design of novel and healthier food to meet both quality requirements and consumer needs. In this context, this review presents the current state of knowledge and new insights for future research concerning FOP of bakery products. The application of FOP in bakery science is new, with different protocols and related evaluation being applied, as detailed in this review. The current knowledge shows that bread structure and texture, influenced by formulation and process conditions, as well as the crust and shortenings present, impact bread breakdown and bolus formation, sensory perception, and food physiological effects such as glycaemic response, satiation, and satiety. For a better comprehension of oral processing, cross-modal perception between sensory attributes is used to understand consumer perception and this is carried out using both in vivo, and in vitro methods. This review highlighted the great potential of FOP to assist researchers and producers to face the current challenges relating to i - salt, fat and sugar reduction in bakery products to fulfil current food nutrition policies, ii - the design of healthier bakery products, and iii - the development of bakery products for consumers with special dietary requirements and ageing needs. In conclusion, FOP shows great potential to assist in the development of novel and healthier foods to meet actual food nutrition policies and consumer needs and should be more explored in bakery science and production.

Functional Breads with Encapsulated Vitamin C and Fish Oil: Nutritional, Technological, and Sensory Attributes

The fortification of bread is considered an effective approach for improving its nutritional properties. However, the incorporation of free bioactive components into bread formulations may affect the overall quality of breads in different ways, depending on the sensitivity of bioactive components to baking factors. In this study, the incorporation of encapsulated vitamin C (ascorbic acid and its salts) and fish oil in breads was investigated for their stability and effect on bread quality. The combination of fish oil emulsions increased the retention of encapsulated ascorbic acid, calcium ascorbate, or sodium ascorbate in breads compared to that of the free non-combined vitamin. At the same time, the combination of vitamin gels increased the retention of docosahexaenoic acid (DHA) and decreased the lipid oxidation in breads compared to the non-combined encapsulated forms. The highest retention values of ascorbic groups, eicosapentaenoic acid (EPA), and DHA were about 70%, 88%, and 95% in breads after baking, respectively. There was the negative correlation between the ABTS radical scavenging capacity and peroxide value in breads. The specific volume of breads was improved by vitamin gels but reduced by fish oil emulsions. Their combination resisted individual impact on the specific volume of breads. The breads with combined ascorbic acid gels and fish oil emulsions showed similar textural properties to the control one. The functional bread with calcium ascorbate gel and fish oil emulsion had the highest moisture content of 45.87%. The inclusion of vitamin gels plus fish oil emulsion decreased free water but increased the bound water. Combining ascorbic acid gels with fish oil emulsions effectively reduced and masked the fishy flavor. The integration of encapsulation techniques and multi-nutrient fortification is proposed as an effective way to enhance the nutritional value and quality of functional bread through synergistic effects.

Effect of modifying pumpkin preparation on oral processing of breads

There is an increasing demand for texture sensations of bread during mastication, with reformulation being needed. This study investigated how bread structure influences oral processing behavior and texture perception. Variations in bread structure were created by manipulating ingredient additions, including pumpkin content and pumpkin processing methods. Results indicated that the physical, chemical, and structural properties drove the oral processing behaviors, and texture sensations were highly correlated with bolus properties. At the beginning and middle of the mastication, bolus from breads with low pumpkin-content required more saliva and exhibited greater hardness, lower adhesiveness, and a higher proportion of small-piece particles than the bolus from high pumpkin-content breads. Bolus from pumpkin pulp breads required more saliva, and was softer, stickier, and generated particles with a lower degree of degradation than the bolus from pumpkin puree breads. However, at the end period, the bolus properties tended to change to similar values. Low pumpkin content breads were initially perceived chewy, whereas high pumpkin content, soft. The dominance rate for soft sensation was higher and lasted longer in breads with pumpkin puree than in breads with pumpkin pulp. Finally, six bread samples were all perceived as hydrated, sticky, and crumbly. This study contributes to a better understanding of the impact of reformulation on oral behavior and sensory properties.

Effect of salivary fluid characteristics on the physical features of in vitro bread bolus: From the absence of saliva to artificially simulated hypersalivation

Saliva facilitates food oral processing, bolus formation, swallowing, and sensory perception, in addition to contributing to oral health and phonation. Ageing, health affections, and polymedication are among many causes altering salivary production, modifying the mastication process, the food impregnation ratio, and in turn altering the characteristics of the bolus, swallowing, and digestion. In this in vitro work, using the AM2 masticator apparatus, which replicates the mechanical actions taking place while chewing solid foods and produces realistic food bolus in various oral conditions, we investigated the effect of salivary fluid characteristics, i.e., composition, quantity (from absence to hypersalivation), temperature, and enzymatic action, on the physical characteristics (i.e., particle size distribution (PSD), bolus mass, salivary fluid content) of in vitro boluses of Traditional French baguette. A ready-to-swallow bolus of baguette displayed on average a d50 value (median particle size by mass) of 4.1 ± 0.4 mm, with saliva fluid constituting ∼ 35 % of the final bolus mass. The absence of saliva in mouth led to a deficient oral processing, forming bread boluses constituted by extremely big particles (ca. 80 % of particles had a size > 7.1 mm) that likely cannot be swallowed safely. On the contrary, an excess of saliva favoured an excessive breaking down of bread, leading to bread boluses constituted by smaller particles than those formed under healthy salivary conditions (d50 decreased from 4.1 mm to 3.1 mm), having a higher salivary fluid content (+10 %). On the other hand, the salivary fluid temperature did not affect PSD, d50, bolus mass, or salivary fluid content of in vitro bread boluses, however, the addition of human salivary α-amylase did, favouring particle size reduction (d50 decreased to 2.6 mm). Therefore, beyond the correlation between bolus hydration by saliva and food properties such as hardness and moisture content, our findings indicate that the quantity of salivary fluid present in the oral cavity and the enzymatic activity of salivary α-amylase during bread mastication significantly influence both the particle size distribution and the fluid content of bread boluses, ultimately determining the physical properties of the bolus and, therefore, potentially impacting the subsequent swallowing process.

Guiding the formulation of soft cereal foods for the elderly population through food oral processing: Challenges and opportunities

As the elderly population is growing steadily, more age-friendly food products that allow them to cover their nutritional needs and are enjoyable need to be designed. Since their oral physiology is considerably altered, the study of Food Oral Processing has become an essential discipline in food development, as it takes into consideration the complex interactions between food structure, oral processing, physiology and perception. Cereals are staple foods in many countries, and their consumption as bakery products is popular among the elderly population. In addition, when fortified with pulse proteins, they can help meet the protein needs of seniors and help fight against sarcopenia. For these reasons, this chapter presents an overview of the various aspects involved in the oral processing and formulation of soft cereal foods, translating them into challenges and opportunities that are of relevance to the design of realistic soft cereal foods targeted for the elderly that are nutritious and sensory appealing. This review focuses on the healthy elderly population and does not intend to cover the needs of the dependent elderly suffering from chronical diseases.