SURVIVAL ANALYSIS TO ESTIMATE SENSORY SHELF LIFE USING ACCEPTABILITY SCORES

ABSTRACT

In the present study, survival analysis was applied on consumers' acceptability scores, focusing the shelf‐life risk on the consumers disliking the product. Shelf life was estimated as the time necessary to reach a fixed percentage of consumers disliking the product, that is, the percentage of consumers scoring the product's overall acceptability below 6 in a 9‐point hedonic scale. In the present work, this methodology was applied to estimate the sensory shelf life of whole pan bread and alfajores. Shelf lives estimated considering 50% of the consumers disliking the product were shorter than those estimated considering consumers' rejection to consume. These results suggest that a proportion of consumers might dislike the sample but still answer “yes” when asked if they would consume the product at their homes. This could be attributed to the fact that when consumers are asked whether they would consume the product, they might think about consuming it after being stored at their homes. In this situation, consumers might be more tolerant toward sensory defects because they do not want to discard the product.

PRACTICAL APPLICATIONS

Sensory shelf life can be estimated using survival analysis considering the percentage of consumers disliking the product. This methodology seems to be a conservative criterion in order to assure the product's quality throughout its storage.     

INFLUENCE OF EDUCATION/PROFESSION OF MEXICAN CONSUMERS ON ACCEPTANCE AND PURCHASE INTENT OF CORN TORTILLA

Influence of education/profession of Mexican consumers on acceptance and purchase intent of corn tortillas was evaluated. Two groups of 150 Mexican consumers each (faculty/graduate students [A] versus field laborers [B]) rated sensory acceptability of corn tortillas. Acceptance and purchase intent were rated using a binomial scale. Group B had higher expectations towards corn tortillas as indicated by lower acceptability ratings. Both groups used rollability, resistance-to-tearing, and chewiness to differentiate tortilla samples, but group B paid more attention to these attributes as indicated by higher canonical correlation values. Acceptance was influenced by overall liking for both groups; chewiness and taste were also significant for group B. Purchase intent was influenced by overall liking and taste for both groups, but color for group A, and appearance and chewiness for group B were also critical. This study demonstrated that education/profession of Mexican consumers affected their acceptance and purchase intent of corn tortillas.

PRACTICAL APPLICATIONS

This study revealed that education/profession of Mexican consumers affected acceptance and purchase intent of corn tortillas. Two groups of consumers with different levels of education had different expectation toward tortillas when making purchase decision. Understanding how each consumer segment differently perceives about the tortilla product will give marketers and manufacturers a better direction for developing tortilla products with expected sensory qualities.     

USE OF THE DISCRIMINANT FUNCTION TO PREDICT THE NUMBER OF CONSUMERS WHO DISCRIMINATE

Three brands of chocolate milk were evaluated for liking, sweetness, creaminess and natural flavor by 48 consumers, using 100mm line scale. The mean sweetness score for one brand was significantly different to the other two and all other attributes were similar. Discriminant analysis on scores from the line scales showed that 63.8% of the evaluations of the least sweet brand (Brand A) were classified by the discriminant function as belonging to the least sweet brand. 19.1% of the scores for Brand B and 17.0% for Brand C were classified as identifying Brand A. A simple count of the number of consumers ranking each brand as least sweet showed that 63.8% chose Brand A, 19.1% Brand B and 17.0% Brand C. This suggests that the discriminant function provides a measure of the proportion of assessors who can tell the difference or, a measure of the degree of confusion between samples.     

SENSORY SHELF-LIFE ESTIMATION OF ALFAJOR BY SURVIVAL ANALYSIS

Survival analysis methodology was used to estimate the shelf life of alfajor (a chocolate‐coated individually wrapped cake) at 20 and 35C by using results obtained from consumers when asked if they would accept or reject samples with different storage times. Sensory acceptability (measured by consumers), off‐flavor (measured by a trained panel) and moisture content were linearly related to time. These correlations were used to estimate values at the shelf‐life times calculated for 25 and 50% rejection probability. Survival analysis provided the following shelf‐life estimation: 74 days at 20C and 33 days at 35C for a 25% of rejection, 87 days at 20C and 39 days at 35C for a 50% of rejection. An alfajor stored at 20C having an acceptability value below 4.9 (1–9 hedonic scale) and off‐flavor intensity above 5.3 (0–10 scale) would be rejected by 25% of the consumers. Chemical data were not good shelf‐life predictors.     

Isolation and properties of Aspergillus niger IBT-90 xylanase for bakery

Xylanase of low molecular weight (K II) was isolated from the fungus Aspergillus niger IBT-90 cultivated in medium with wheat bran. K II was purified by precipitation with ammonium sulphate (20–80% saturation) and gel filtration on Biogel P-10. This enzyme is most active in hydrolysis of birchwood xylan at 50°C and pH 5.5. Xylanase K II has an ability to degrade 1,4-β-bonds and to debranch substrates. It degrades not only xylans but also cellulose, an important factor for its application in bakery. Ag⁺, Fe³⁺ and NBS are strong inhibitors of the enzyme. DTT and Na⁺ activate xylanase K II by 24 and 13%, respectively. Enzyme K II used as additive to flour improves dough properties, increases the volume of wheat–rye and whole meal bread, and increases the porosity of crumb and the moisture of the final product, consequently extending the shelf life of bread.     

EPISTATIC INTERACTIONS CAN LOWER THE COST OF RESISTANCE TO MULTIPLE CONSUMERS

It is widely assumed that resistance to consumers (e.g., predators or pathogens) comes at a “cost,” that is, when the consumer is absent the resistant organisms are less fit than their susceptible counterparts. It is unclear what factors determine this cost. We demonstrate that epistasis between genes that confer resistance to two different consumers can alter the cost of resistance. We used as a model system the bacterium Escherichia coli and two different viruses (bacteriophages), T4 and Λ, that prey upon E. coli. Epistasis tended to reduce the costs of multiple resistance in this system. However, the extent of cost savings and its statistical significance depended on the environment in which fitness was measured, whether the null hypothesis for gene interaction was additive or multiplicative, and subtle differences among mutations that conferred the same resistance phenotype.     

Use of Lineal-Path Distribution Function as Statistical Descriptor of the Crumb Structure of Bread

The importance of the relation between food microstructure and their quality is recognized as crucial. In terms of bread quality, the precise characterization of the crumb structure is considered essential to evaluate its sensorial properties. A variety of different statistical correlation functions have been theoretically formulated in recent years to quantify the microstructure of general random heterogeneous materials but they have rarely been applied in food science. In this paper, we have developed a method to calculate the lineal-path distribution function L(x) for the void and solid matrix phases from two-dimensional (2D) images of bread. The method has been successfully employed here to characterize the microstructure for two type of commercial breads. Our results reveal that crumb structure may be modeled as a system of polydispersed overlapping disks. Moreover, we have quantified the dimensions of the voids and crumb phase statistically and differences in the homogeneity of crumb structure.     

CONSUMER'S COLOR ACCEPTANCE OF STRAWBERRY NECTARS FROM PUREE

In two surveys (600 consumers) (1) the importance of color on a consumer's decision to buy strawberry nectar and jam, (2) the consumer's color acceptance of strawberry nectars from puree and adequate products containing colorants from the market as well as specially prepared samples and (3) the associated attributes to these samples were studied. In addition, a test was carried out in order to (4) characterize strawberry color and its changes during storage sufficiently with one value.
Color has a big impact on a consumer's decision to buy strawberry nectars as well as strawberry jam. Neither gender nor age or consumption habits of consumers had a significant impact on color acceptance. For color assessment, an "acceptance factor" (AF) was calculated from colorimetric data that provides processors the prediction of color quality of nectars from puree. Nectars with an AF lower than 0.4 were not accepted, whereas nectars with an AF higher than about 0.7 were described as excellent.

PRACTICAL APPLICATIONS

The results of this study show the first time that it is possible to characterize the color of strawberry products by means of the calculation of an "acceptance factor" (AF =  a */h), and to predict whether the color will be accepted from the consumers or not (excellent [AF > 0.7], acceptable [AF > 0.4] or not acceptable [AF < 0.4]). This data could be used as basis for the production of new strawberry nectars (containing colorants) and the assessment for the stability and shelf life of strawberry products from puree.     

Effects of Acidification, Sodium Chloride, and Moisture Levels on Wheat Dough: II. Modeling of Bread Texture and Staling Kinetics

The effect of three experimental factors pH (addition of lactic acid and sodium hydroxide), water, and sodium chloride (NaCl) addition on wheat bread making performance (volume, baking loss, crumb firmness, crumb grain features) and the crumb staling during storage was studied. The staling behavior was modeled with the Avrami equation and with linear regressions. All bread quality parameters were reliably modeled using response surface methodology (up to R ² ?=?0.97). The crumb staling behavior was better described by a linear regression than by the rate constant k of the Avrami equation (R ² ?=?0.87 / R ² ?=?0.36). The highest volume can be achieved with the experimental values pH 5.39, 0.41?g NaCl 100?g^?1 flour and 68.7?g water 100?g^?1 flour. Correlation analysis revealed significant linear dependency of dough rheology (complex shear modulus) on the firmness of the bread crumb (r?=?0.73) and staling attributes (r????0.73). Dough microstructural properties showed significant but low correlation with bread making performance attributes.     

PREFERENCES FOR SOUTHWESTERN SALTED SNACK FLAVORS: INDIVIDUAL DIFFERENCES AT THE CONCEPTUAL LEVEL AND THE CONSTRUCTION OF A PRODUCT LINE

Individuals differ in what they like, both from a sensory basis, but also from a conceptual basis. For a product to be purchased, the concept (or even the flavor name) must be acceptable just as the physical product itself must be acceptable. This paper presents the results of a study in which the panelists rated degree of interest in 12 different new flavors for a snack chip positioned at the start of the study to have a "taste of the southwest." The results show the substantial variation in acceptance for the different flavors presented as names only (viz., concepts, rather than actual products). Segmentation by attitude of consumers on the basis of the pattern of liking revealed differences among consumers, but did not show the typical opposing patterns found when sensory segmentation is done using actual products having different flavors. These individual differences require that a line of different flavors be developed. There is no simple organizing principle, however, underlying the individual differences. Thus to create the line of flavors requires a different approach. The approach selects various combinations of flavors, identifies the proportion of consumers who would accept at least one flavor of the line (so-called "satisfied consumer"), and then maximizes the number of such "satisfied consumers" for a line comprising a given number of flavors.     

Use of immobilized cell biocatalysts in baking

Baking using baker's yeast immobilized in a starch–gluten–milk matrix (traditional fermented cereal food trahanas), containing viable lactic acid bacteria (LAB), and kefir (natural co-culture of yeasts and LAB) immobilized on orange peel, were investigated. The use of immobilized cells increased shelf life, delayed staling, and improved overall the quality of bread, compared with the traditional baker's yeast bread. These improvements were attributed to the reduction of pH, the lower moisture loss rates, and the presence of LAB, which are known to exhibit antimould properties. Better results were obtained using the sourdough method compared to the straight dough bread-making method. Headspace SPME GC–MS analysis showed that the use of immobilized cells increased the number of bread aroma volatiles, especially esters. The best results, including shelf life and overall bread quality, were obtained in the case of baker's yeast immobilized on trahanas, although kefir immobilized on orange peel seems to be a more cost effective biocatalyst.     

The behavioral economics of consumer brand choice: patterns of reinforcement and utility maximization

Purchasers of fast-moving consumer goods generally exhibit multi-brand choice, selecting apparently randomly among a small subset or "repertoire" of tried and trusted brands. Their behavior shows both matching and maximization, though it is not clear just what the majority of buyers are maximizing. Each brand attracts, however, a small percentage of consumers who are 100%-loyal to it during the period of observation. Some of these are exclusively buyers of premium-priced brands who are presumably maximizing informational reinforcement because their demand for the brand is relatively price-insensitive or inelastic. Others buy exclusively the cheapest brands available and can be assumed to maximize utilitarian reinforcement since their behavior is particularly price-sensitive or elastic. Between them are the majority of consumers whose multi-brand buying takes the form of selecting a mixture of economy -- and premium-priced brands. Based on the analysis of buying patterns of 80 consumers for 9 product categories, the paper examines the continuum of consumers so defined and seeks to relate their buying behavior to the question of how and what consumers maximize.     

SHELF-LIFE ESTIMATION OF APPLE-BABY FOOD

The aim of the present work was to study the evolution of the color of an apple‐baby food and to estimate its sensory shelf life. Samples of apple‐baby food stored at 25C were analyzed using trained assessors and a consumer panel. A zero‐order reaction kinetics was found for the evolution of sensory color with storage time. Color was highly correlated with consumers' rejection percentage and overall acceptability, which indicates that consumers consider this attribute when deciding to accept or reject this product and in assigning their acceptability scores. Using this correlation, the sensory cutoff point for color, corresponding to a 25% consumer rejection, was calculated. Sensory shelf life was estimated using consumer data. Sensory shelf life estimated by survival analysis was in agreement with that calculated considering an acceptability limit of 6.0 in a 9‐point hedonic scale.     

Odorant transfer characteristics of white bread during baking

The potent odorants in the crust and crumb of white bread were identified and quantified by gas chromatography-mass spectrometry and gas chromatography/olfactometry. The weight loss ratio of the samples baked at 220 °C was controlled in the range of 0-28%. The odorants were classified into 5 types by the transfer characteristics: i) All amounts of odorant transferred from the crust to external space (type-I). ii) All transferred from the crust to the crumb and external space (type-II). iii) Certain amount remaining in the crust and the rest transferred to the crumb and external space (type-III). iv) All transferred from the crumb to external space (type-IV). v) Certain amount remaining in the crumb and the rest transferred to the crust and external space (type-V). The odorants of type-IV were not apparent after the crust had formed. The results indicate that the crust could be a barrier to prevent the odorants from being transferred to external space.     

Promoting sustainability in Mexico’s building sector via environmental product declarations

Purpose

The growing phase of emerging economy countries requires the implementation of environmental assessment tools in the building sector. The use of environmental product declarations (EPDs) has risen in developed countries as one of the main tools for environmental assessment. However, at what point should developing countries follow the EPD implementation strategies used by developed countries? What are the strengths and weaknesses of EPD in the emerging economy context, and what threats and opportunities does it face within the building sector? This work aims to answer these questions by taking Mexico as a case study.

Methods

A bibliographical review was conducted to determine the key elements for EPD development in the building sector in other countries, especially those in Europe, where EPDs originated. The review also examined the experience and perspective of other countries that are starting to contemplate this type of ecolabel as an option for environmental assessment within their own building sectors, as well as industry perspectives on EPDs, especially those of small and medium-sized enterprises (SMEs). Then, Mexico’s situation in regard to these key elements was examined, with a special focus on the main stakeholders detected: government and industry. Finally, after a contrast analysis was conducted between the developed countries and Mexico, the strengths and weaknesses of EPDs in the emerging economy context and the threats and opportunities within the building sector were determined.

Results and discussion

The use of EPDs in Europe has largely followed a normative and legislative pattern. Moreover, it has been the main data source for building environmental assessment schemes, and there is a strong life cycle assessment (LCA) platform that contributes to EPD development. Furthermore, there is a European tendency toward making the use of EPDs mandatory. However, there is a very different reality in emergent economy countries. In these countries, social housing represents a major part of the vision of the building sector, so it is taken as an initial approach to EPD development. In Mexico, there is a solid legislative framework in which EPDs could be implemented, and there is a variety of environmental assessment housing programs into which EPDs could be integrated. Nevertheless, there is an institutional void that has prevented the incorporation of the life cycle approach into the national strategy of sustainability in the building sector. Moreover, SMEs might not have the technical and financial capacity to develop EPD.

Conclusions

This analysis has proved that EPD implementation in emerging countries mainly depends on two aspects: Firstly, it must be a shared vision of sustainability between government and industry, in which there is a correspondence between the sustainability objectives of the two parties and SMEs have the ability to contribute toward their achievement. Secondly, a solid platform of knowledge that supports LCA in the building sector is necessary, and it must involve a strong relationship between government, academia, and stakeholders.