Oral Processing Studies: Why Multidisiciplinary?

When food is ingested, it remains in the mouth for a short period of time. Although this period is brief compared to the total food nutrient digestion and absorption time, it is crucially important as it is the first step in digestion. It is also very important that, while the food is in the mouth, it is perceived by the senses and then a decision is made on swallowing. Oral sensory perception is an integrative response, which is generated in very short time (normally a few seconds) from complex information gathered from multiple sources during mastication and swallowing. Consequently, food oral processing studies include many orientations. This Special Issue brings together a small range of studies with a diversity of approaches that provide good examples of the complexity and multidisciplinarity of the subject.

Are mixed meat and vegetable protein products good alternatives for reducing meat consumption? A case study with burgers.

The principal motivations for the worldwide trend towards reducing meat consumption are health, the environment and animal welfare. The present study investigated the willingness of omnivores to introduce mixed (beef-vegetable protein) and 100% vegetable protein products into their diet. The participants (n = 251) were young adult omnivores who consumed meat at least once a week. The stimuli were images of six different products representing two beef burgers, two mixed-protein burgers (50% beef and 50% seitan or soy) and two 100% vegetable protein burgers (seitan and soy). The participants were asked to write down spontaneous associations with each product (Word Association technique) and score their expected liking and purchase intention for them. In addition, they completed a questionnaire (36 statements) to evaluate their attitude towards meat reduction, considering six aspects: diet, habits, ethics, hedonism, health, and the environment. According to their response to these statements, they were classified into three attitude groups: anti- (ANTI, n = 106), intermediate- (INTERM, n = 89), and pro- (PRO, n = 56) meat reduction. All the participants expected to like the 100% beef burger most, the PRO group expected to like all six products to a similar degree and the ANTI group expected to like the mixed product significantly more than the 100% vegetable product, indicating that the introduction of mixed proteins could be a small first step towards meat reduction for those most attached to meat. The associations elicited by the different burgers were mostly the same but were mentioned with different frequencies, which also depended on the attitude group. These distinctive association patterns showed clear connections to the motives underlying each group's attitude towards meat reduction. It may be concluded that mixed products would be a reliable although timid option for consumers who are attached to meat to reduce their meat intake, while any of the products containing vegetable proteins would be an option for consumers who are more favourable towards meat reduction.

Do Consumers Change Their Perception of Liking, Expected Satiety, and Healthiness of a Product If They Know It Is a Ready-to Eat Meal?

A ready-to-eat meal is a prepared meal within a container or package that requires little preparation or heating before consumption. Despite ready-to-eat meals being widely consumed, to date, little information is available on the consumers' perceptions of such products in comparison to a homemade meal. Thus, three groups of eighty participants took part in the present study; each group evaluated five ready-to-eat meals (Pasta, Meatballs, Salad, Beans, and a Sandwich) using one of the following conditions: (i) observation of the packaging, (ii) observation of the meal on a plate (photographs), and (iii) tasting the ready-to-eat product with the packaging being presented alongside the meal. Consumers were asked about their liking, satiety, and healthiness perception. The results showed that both the ready-to-eat pack and sensory quality of the product highly impact liking and healthiness perceptions. Being a ready-to-eat meal in a pack has a negative impact on liking expectations of the meal; however, the sensory quality can either counteract these effects or increase them. Expected satiety of meals depends on the type of meal and varies slightly according to the evaluation condition.

Evaluation of Some Ingredients and Energy Content on Front-of-Pack Cereal Bar Labeling as Drivers of Choice and Perception of Healthiness: A Case Study with Exercisers.

The objective of this study was to explore the drivers of choice and perceptions of healthiness that specific ingredient or energy content information displayed on the front-of-pack label of cereal bars triggers among different groups of consumers. The participants (18 to 50 years old), classified as exercisers (n = 103, 52 women) or nonexercisers (n = 101, 51 women), completed a questionnaire and then rated their interest using images of cereal bars that varied in four characteristics ("With fruit," "With chocolate," "High protein," and calorie content). Conjoint analysis showed that the most important motives were associated with the convenience, pleasure/indulgence and liking dimensions, which did not differ between groups. These were followed by two other motives introduced in this study: energy/physical activity and satiety, in which the exercisers showed a distinctively higher level of interest than the nonexercisers. Chocolate and a low calorie content were the outstanding drivers of interest, at similar levels for both groups. A high protein content claim increased the interest of all participants, but more so for exercisers and for men. Fruit had a low impact on interest, which was only significant for women. These results indicate that front-of-pack label information influences choice in a distinctive way for some targeted population groups. PRACTICAL APPLICATION: This study contributes knowledge about the impact that front-of-pack label information about certain ingredients and the energy content has on the motives and drivers for snack choices and perceptions of healthiness. The results contribute interesting results on the behavior of some consumer segments, in particular, exercisers and people involved in fitness activities, who are supposed to have special dietary needs.

Potential Impact of Oat Ingredient Type on Oral Fragmentation of Biscuits and Oro-Digestibility of Starch-An In Vitro Approach.

The aim of the present study was to determine how variation in the biscuit matrix affects both the degree of in vitro fragmentation and the starch hydrolysis that occurs during the oral phase of digestion. Using three different oat ingredient types (oat flour, small flakes, and big flakes) and baking powder (or none), six biscuits with different matrices were obtained. The instrumental texture (force and sound measurements) of the biscuits was analyzed. The samples were then subjected to in vitro fragmentation. The particle size distribution and in vitro oral starch hydrolysis over time of the fragmented samples were evaluated. The results showed that the samples presented different fragmentation patterns, mainly depending on the oat ingredient type, which could be related to their differences in texture. The biscuits made with oat flour were harder, had a more compact matrix and showed more irregular fragmentation and a higher percentage area of small particles than those made with big oat flakes, which were more fragile and crumbly. The highest degree of starch hydrolysis corresponded to the biscuits made with flour. Conclusions: Differences in the mechanical properties of the biscuit matrix, in this case due to differences in the oat ingredient, play a role in the in vitro fragmentation pattern of biscuits and in the oral phase of starch hydrolysis.

The dynamics of texture perception of hard solid food: A review of the contribution of the temporal dominance of sensations technique.

The present paper reviews the use of temporal dominance of sensations (TDS) sensory methodology in relation to texture evaluation. From more than 100 papers initially screened, 28 dealing with the texture of hard solid foods that require mastication were selected. The attributes evaluated by TDS were comprehensively analyzed and the phases of the mastication period in which they occurred were studied. The relation between these attributes and the initial mechanical food properties, the particle size, shape, and aggregation of the increasingly destroyed food structure, and the evolving properties of the bolus through to swallowing were also examined. Results from complementary techniques used alongside TDS, both sensory and nonsensory, were also analyzed. The contribution of TDS methodology to understanding the texture construct is shown to be reliable and suggestions are made for future lines of research. PRACTICAL APPLICATIONS: The literature on the temporal dominance of sensations method is constantly increasing. The present review examines the application of this method to the dynamics of texture perception of hard solid foods. The key texture attributes perceived in each phase of mastication, together with their relation to the initial food structure, gradual comminution, and bolus formation, will shed light on the usefulness of this methodology for food texture appraisal.

Impact of composition and texture of protein-added yogurts on oral activity.

Understanding how oral processing is altered in response to changes in the composition and mechanical properties of food provides useful information to design food with improved satiating capacity which is largely influenced by oral exposure. In turn, this information deepens the knowledge about the physiology of texture perception. Six yogurts were formulated with different amounts of protein and protein sources and addition of apple cubes: control (C), extra skimmed milk powder-added (MP), whey protein isolate-added (WPI), and whey protein microgels-added (WPM). In addition, MP was also added with maltodextrin (MPMD) and with fresh apple cubes (MPF). Activities of masseter, anterior temporalis and anterior digastric muscles during oral processing of each sample were recorded (electromyography), and jaw movement amplitudes in three dimensions were determined (jaw tracking system). The jaw muscle activities were highly dependent on the type of yogurt. Addition of apple cubes (MPF) almost doubled the oral processing time, number of chews, and muscle activity of all samples. MP and MPMD required similar but lower values of oral processing than MPF attributed to their reinforced network of milk protein. The lowest values were found for WPI, C and WPM, indicating a weaker, more fluid material. These behavioral results, which clearly differentiate the samples, are discussed in connection to the rheological and sensory properties of the yogurts. This study suggests that adding apple cubes significantly alters the oral processing pattern, such that they may be a more effective way of increasing the oral processing time (time exposure) compared to more subtle changes in the protein amount or source. Nevertheless, changes in the protein amount and source also affected, although to a lesser extent, the behavioral, rheological, and sensory properties of yogurt.

The Role of the Dynamic Sensory Perception in the Reformulation of Shakes: Use of TDS for Studying the Effect of Milk, Fiber, and Flavor Addition.

Various factors need to be taken into account when reformulating a food or beverage. The food components, not only macronutrients but also minor ingredients such as flavoring agents, could affect the perception of the sensory sensations, importantly their dynamic aspects, as rising and duration, which are not normally considered. The novelty of this approach is the study of the effects of the addition of several ingredients (fiber, extra milk powder, and strawberry flavoring) on the dynamic perception of a food item (strawberry shakes) using the temporal dominance of sensations (TDS) technique. The occurrence and duration of the key sensory sensations (acid, natural strawberry flavor, thick, sweet, candy strawberry flavor, and milk flavor) extracted from the TDS curves were analyzed and linked to the composition factors and liking and expectations of satiety scores. For example, the addition of flavoring increased the liking scores (increments ranging from 0.3 to 1.1) that was linked to the attenuation of acid sensation; and the addition of extra milk powder increased the expectation of satiety scores (increments ranging from 0.5 to 0.7) that was linked to the perception of early thick sensation in the mouth. In general, the more complex sensory profiles the higher liking and expectations of satiety. PRACTICAL APPLICATION: This work is a case study on how temporal sensory methods can contribute important information on the actual perception of food during consumption. Depending on the ingredients added these sensory properties appear at different times and with different dominance during evaluation affecting liking or fullness expectations. In consequence, the temporal sensory properties should be taken into account when designing or reformulating food.

Recommendations for characterization and reporting of dietary fibers in nutrition research.

Dietary fiber (DF) comprises a wide range of naturally occurring and modified materials with substantial variations in physical and chemical properties and potential physiologic effects. Although nutrition studies testing the effects of DF usually provide extensive detail on the physiologic responses, many still fail to adequately report the type and properties of the DF itself. This weakens the ability to directly replicate and compare studies and to establish structure-function relations. We outline the factors that affect DF functionality and provide 4 overarching recommendations for the characterization and reporting of DF preparations and DF-containing foods in nutrition research. These relate to 1) undertaking characterization methods that reflect the study hypothesis; 2) adequate reporting of DF source, quantity, and composition; 3) measurement of DF rheological properties; and 4) estimation of the DF fermentation rate and extent. Importantly, the food matrix of the test products should also be considered, because this can influence DF functionality and hence the apparent DF efficacy for health-relevant outcomes. Finally, we point out differences in DF functionality to be considered in acute and longer-term trials, the need to design the control treatment according to the research question, and the importance of reporting the amount and type of DF in the background diet.

Expectations of food satiation and satiety reviewed with special focus on food properties.

Expectations of satiation are beliefs about the extent to which food is expected to deliver fullness and expectation of satiety relates to the extent to which food is expected to give respite from hunger and to inhibit further eating. In recent years they have increasingly been investigated because of the interest in how they can modulate energy intake. The present paper reviews the body of research into concepts underlying these expectations, measurement methods and the factors influencing their perception, with special focus on the sensory features and composition of foods. Food science and technology can provide tools and knowledge to aid in designing food with enhanced expectations of satiation and satiety.

The role of starch and saliva in tribology studies and the sensory perception of protein-added yogurts.

Increasing the protein content of yogurts would be a good strategy for enhancing their satiating ability. However, the addition of protein can affect product palatability, contributing astringency or an inhomogeneous texture. Increasingly, studies mimicking oral tribology and oral lubrication have been attracting interest among food researchers because of their link with oral texture sensations. In the present study, four double-protein stirred yogurts were prepared by adding extra skimmed milk powder (MP) or whey protein concentrate (WPC) and by adding a physically modified starch to each (samples MPS and WPCS, respectively) to increase the consistency of the yogurts. The lubricating properties of the four yogurts were examined by tribological methods with the aim of relating these properties to the sensory perception described by flash profiling. Samples were also analysed after mixing with saliva. The tribology results clearly showed that addition of starch reduced the friction coefficient values regardless of the type of protein. Saliva addition produced a further decrease in the friction coefficient values in all the samples. Consequently, adding saliva is recommended when performing tribology measurements of foods in order to give a more realistic picture. The sensory results confirmed that the addition of starch reduced the astringent sensation, especially in sample WPC, while the MP and MPS samples were creamier and smoother. On the other hand, the astringency of sample WPC was not explained by the tribology results. Since this sample was described as "grainy", "gritty", "rough", "acid" and "sour", further studies are necessary to investigate the role of the number, size, shape and distribution of particles in yogurt samples, their role in astringency perception and their interaction with the perception of the tastes mentioned. Oral tribology has shown itself to be an in vitro technique that may aid a better understanding of the dynamics of in-mouth lubrication and the physical mechanisms underlying texture and mouthfeel perception.

Importance of consumer perceptions in fiber-enriched food products. A case study with sponge cakes.

Sponge cakes enriched with fiber from different sources (maltodextrin, wheat, apple, blackcurrant and a mixture of potato and Plantago ovata) were studied. Profiling of the different cakes was carried out, first using a check-all-that-apply (CATA) question then evaluating the consumers' likings using a hedonic scale. The consumers also completed a nutrition knowledge (NK) questionnaire that was used to classify them according to their NK level. The instrumental texture of the cakes was evaluated by the texture profile analysis (TPA) method. The consumers' response was not linked to their NK level, but it mainly depended on the importance they gave to the cakes' distinctive sensory characteristics. In general, liking increased for samples considered easy to chew, spongy, soft and sweet, and decreased for samples perceived as tasteless, dry or having a fruity or an odd flavor. The sponge cakes containing maltodextrin or wheat fiber, which mostly resembled a conventional cake, were the most liked in general. Those containing the other three fibers were rejected by part of the consumers, for being tasteless in the case of potato plus Plantago ovata fiber, for being dry and doughy in the case of apple fiber and for having an odd flavor in the case of blackcurrant fiber.

A review of the characteristics of dietary fibers relevant to appetite and energy intake outcomes in human intervention trials.

Background: Many intervention studies have tested the effect of dietary fibers (DFs) on appetite-related outcomes, with inconsistent results. However, DFs comprise a wide range of compounds with diverse properties, and the specific contribution of these to appetite control is not well characterized.Objective: The influence of specific DF characteristics [i.e., viscosity, gel-forming capacity, fermentability, or molecular weight (MW)] on appetite-related outcomes was assessed in healthy humans.Design: Controlled human intervention trials that tested the effects of well-characterized DFs on appetite ratings or energy intake were identified from a systematic search of literature. Studies were included only if they reported 1) DF name and origin and 2) data on viscosity, gelling properties, fermentability, or MW of the DF materials or DF-containing matrixes.Results: A high proportion of the potentially relevant literature was excluded because of lack of adequate DF characterization. In total, 49 articles that met these criteria were identified, which reported 90 comparisons of various DFs in foods, beverages, or supplements in acute or sustained-exposure trials. In 51 of the 90 comparisons, the DF-containing material of interest was efficacious for ≥1 appetite-related outcome. Reported differences in material viscosity, MW, or fermentability did not clearly correspond to differences in efficacy, whereas gel-forming DF sources were consistently efficacious (but with very few comparisons).Conclusions: The overall inconsistent relations of DF properties with respect to efficacy may reflect variation in measurement methodology, nature of the DF preparation and matrix, and study designs. Methods of DF characterization, incorporation, and study design are too inconsistent to allow generalized conclusions about the effects of DF properties on appetite and preclude the development of reliable, predictive, structure-function relations. Improved standards for characterization and reporting of DF sources and DF-containing materials are strongly recommended for future studies on the effects of DF on human physiology. This trial was registered at http://www.crd.york.ac.uk/PROSPERO as CRD42015015336.

Yogurt viscosity and fruit pieces affect satiating capacity expectations.

The extent to which a food is expected to deliver satiation is called expected satiation. Many factors affect this expectation, including a number of sensory properties such as texture. The present study explores the relationships between two kinds of texture variations in a yogurt and its expected satiating capacity (ESC). One texture variation consisted in adding three types of pineapple particles: fresh pineapple purée (+PP samples), small cubes of fresh pineapple (+PF samples), and small cubes of lyophilized pineapple (+LP samples). The other texture variation was the viscosity of the yogurt base: yogurt thickened with starch (high viscosity yogurt, HVY-samples) and without starch (low viscosity yogurt, LVY-samples). A total of 8 samples were obtained: the two basic yogurts without added fruit (sample LVY and sample HVY), and each of these with one of the three kinds of pineapple particles (samples LVY+PP, LVY+FP, LVY+LP, HVY+PP, HVY+FP and HVY+LP). A total of 98 consumers described the sensory characteristics of the 8 yogurts on a CATA questionnaire and evaluated the expected satiating capacity (ESC) and acceptability that the yogurts elicited. In addition, the consumers were asked about the characteristics they had considered when evaluating the ESC of the samples. Correspondence Analysis was used to understand how the consumers perceived and described the differences in yogurt texture. Penalty Analysis and Partial Least Squares regression were conducted to explain the differences in ESC among the yogurt samples and to determine the attributes that had significant positive and negative effects. The results indicated that starch addition (a more viscous product base) increased the mean ESC values regardless of the pineapple particle added. This could be attributed to more extensive oral handling due to the creaminess and mouth coating contributed by these yogurts. Second in importance for higher ESC perception was the presence of lyophilized pineapple cubes, which required some chewing before swallowing since they are dry and crispy. The attributes that were related more to ESC were principally those associated with the yogurt base texture (creamy, mouth coating, consistent, dense, fatty, thick and homogeneous) and others related to the fruit added, such as integrated texture or pleasant fruit pieces.

Consumer perception of carriers of a satiating compound. Influence of front-of-package images and weight loss-related information.

Nowadays it is common to find dietary supplements on the market with the same health promoting compounds as certain functional food products. However, there is a lack of research comparing these two categories of carriers (food and supplements) for the same functional ingredient. This work focuses on konjac glucomannan (KGM) due to its recognized body weight reduction-related effect: when it swells in the stomach in the presence of sufficient water, it produces a sensation of fullness. In this context, the objectives of the present work were to gain knowledge about consumer perception of KGM and its different carriers or forms of presentation (in a food item or in capsules). In addition, the relative importance of the carrier, front-of-package images and weight loss-related information were studied by different sensory techniques, such as word association, projective mapping and conjoint analysis. The results showed that consumers formed negative perceptions when the information was not sufficiently complete and that they considered a food product containing KGM better than KGM capsules. Regarding the front of the package, health benefit-related images were more attractive than verbal information.

Does food complexity have a role in eliciting expectations of satiating capacity?

New strategies for formulating healthy, balanced food with enhanced expected satiating capacity are a hot topic. The present work tests the hypothesis that adding complexity to food will result in higher expectations of satiating capacity. Different kinds of "visible" particles (wheat bran, ground coconut, flaxseeds and oat meal) were added to cheese pies with the aim of increasing the complexity of both their appearance and their texture. Two more basic recipes were also prepared with no particles added. Instrumental texture measurements, complexity and expected satiating capacity consumer scoring and sensory profiling of the six pie formulations were performed. In addition, the consumers were asked to write down the characteristics they took into account in their pie complexity scores. For pies with very similar instrumental TPA hardness and resistance to penetration values, a clear trend that emerged was that the more complex the texture, the higher the satiating capacity expectations. The qualitative analysis of the terms mentioned by consumers was of great value for understanding the concepts underlying the appraisal of the samples' complexity.

Consumer perceptions of satiating and meal replacement bars, built up from cues in packaging information, health claims and nutritional claims.

Previous research has shown that consumers' sensory and hedonic perceptions could be greatly influenced by the messages highlighted on the front of the packaging, particularly nutrition and health claims for reduced-calorie or functional foods. In food products designed for hunger control, mentioning satiating effects or meal replacement could potentially influence the expected satiety or other perceptions, including those associated with a filling effect. This study investigated the effect of packaging information on consumer perceptions of eleven commercial chocolate-flavoured satiating and meal replacement bars. Projective mapping (Napping®) with a descriptive step was used to profile the expectations elicited by the eleven bars, based on their extrinsic characteristics (without tasting them), with two different groups of consumers in two different scenarios: mapping the samples' packaging and mapping cards with an identical design showing the most important information displayed on the packaging (product name, nutrition information panel and nutrition and health messages or claims). The terms and comments obtained in the two scenarios were analysed and perceptual spaces were generated from the sample location and attributes obtained in the Napping® exercises, using multi factor analysis (MFA). The results showed that when evaluating the real packaging, the consumers mainly focused on the meal replacement- or satiation-related messages and on the images to build up their perception, attaching less or no importance to the nutritional information that was also displayed on the box. When examining the packaging, sensory expectations - which probably emerged from the images of the bars - were also a very important factor in placing the samples in the perceptual space. When looking only at the cards, the consumers' grouping and attribute generation focused in great detail on the nutritional information. The calorie content also became a much more important factor in their perceptions of the bars. Interestingly for the product category analysed, messages about "satiating" and "meal replacement" effects were clearly distinct and negatively correlated in the consumers' minds.

Specific phenolic compounds and sensory properties of a new dealcoholized red wine with pomegranate (Punica granatum L.) extract.

The pomegranate (Punica granatum L.) fruit has a long history of human consumption and possesses notable antioxidant and cardiovascular properties. This work evaluated the feasibility to provide a new functional beverage based on a dealcoholized red wine matrix supplemented by a pomegranate extract. The potential bioactive compounds in the pomegranate extract, punicalagin A and B and ellagic acid, were analyzed during the downstream process in order to evaluate the functional dose in the final beverage. The addition of pomegranate extract to the dealcoholized red wine resulted in a product with more intense yeast odor, acidity, yeast flavor, and astringency and with a less intense berry flavor. Consumer acceptance of the product was also investigated and the results revealed the existence of a niche of consumers willing to consume dealcoholized wine enriched with pomegranate extract. After tasting, 50% and 40% of those consumers initially interested by this product concept declared to be interested to purchase the control sample and the functional beverage, respectively. The daily consumption of two servings of 250 mL of this new pomegranate-enriched dealcoholized wine provides 82 mg of total ellagitannins, corresponding to the sum of punicalagin A and B and ellagic acid.

Microwave heating effect on rheology and microstructure of white sauces.

The microstructure and rheological properties of white sauces formulated with different starches were analyzed after being microwave-heated for different times. Significant differences (P < 0.05) in rheological parameters analyzed-storage modulus (G'), loss modulus (G″), and loss tangent (tanδ)-were obtained for sauces made with different starches. Microwave reheating did not affect G' and G″ values until water evaporation became significant. In addition, tanδ values did not change significantly (P < 0.05) even during long reheating times showing that sauce viscoelastic properties did not change after microwave irradiation. However, microstructure assessed by confocal laser scanning microscopy showed changes in fat globule and protein. These microstructural changes did not seem to have a significant effect on rheological measurements since starch and ι-carrageenan are mainly responsible for the viscoelastic behavior of the sauces. Practical Application: The development of products appropriate to microwave heating is constantly rising in food industry. It is necessary to understand the behavior of the ingredients and the final product to microwave heating in order to choose those ingredients which will develop the best performance. Starches are common ingredients in industrial sauces, and rheological and microstructural techniques have shown their usefulness in characterization of starch-based systems.

Thermal Degradation of Green Asparagus Texture.

A cutting cell was developed to evaluate the texture of green asparagus by measuring its resistance to being cut with a wire. The cell was used in conjunction with a universal texturometer and improved on the single-point method of the Wilder fibrometer. Experimental conditions were determined for using the cell to measure the cutting resistance of asparagus subjected to different extents of heat treatment. Better discrimination between samples was obtained than with a Kramer cell. The fresh asparagus spears. were heated at temperatures between 70 and 100°C for different lengths of time and the kinetics of the degradation of texture was studied. A biphasic (two-component) behavior was observed with each component displaying first-order kinetics, The kinetic parameters calculated by measuring the texture with the wire cell (cutting at a position 5 em from the tip of the asparagus) were Eaa = 9.56 and Eab = 20.43 kcal/mol (activation energy for components A and B), and ka85 = 1.047 and kb85 = 0.057 min-1 (rate constants for A and B of asparagus heated at 85°C). When the texture was determined by measuring the shear force with a Kramer cell, the parameters estimated were Eaa = 23.41 and Eab = 18.32 kcal/mol, and ka85 = 0.25 and kb85 = 0.025 min-1 Both the wire cell cutting method and the Kramer shear-press method are suitable for evaluating the degree of thermal softening of green asparagus heated to temperatures between 70 and 100°C.