Mechanical parameters to assess quality changes in cherimoya fruit

 Several mechanical parameters obtained by means of compression and penetration tests, and changes in cherimoya (Annona cherimola Mill.) fruit quality during storage in air and two controlled atmospheres (CA), (3% O₂+0% CO₂ and 3% O₂+3% CO₂) were analysed. A gradient of softening was found among the equatorial and the apical areas of the flesh during CA storage, as assessed by localized penetration tests. The combination of low O₂/elevated CO₂ (3% O₂+3% CO₂) increased this gradient and had a greater inhibiting effect on skin softening than low O₂. It appeared that the prevention of softening by CA was stronger in the less mature tissues (equatorial and outer areas) than in the more mature tissues (apical and inner areas around the longitudinal axis). CA delayed or inhibited changes in fruit quality observed during air storage: increases in total soluble solids (TSS), titratable acidity (TA), and yellowness of the flesh (b), and diminution in flesh lightness of colour (L). A good relationship between an objective quality index (QI, where QI=TSS+TA+L/b) and the compression slope (CS) was found during storage under all the conditions tested. It is suggested that the relationship, QI=29.25+0.04×CS–0.0023×CS² could be useful when assessing stages of cherimoya fruit quality during storage under different conditions by performing a nondestructive, compression test. Received: 23 April 1998     

Optimization of low-temperature blanching for retention of potato firmness: Effect of previous storage time on compression properties

Low-temperature blanching (LTB) of potatoes (cv. Kennebec), both without further processing and prior to cooking or freezing + cooking, significantly increased firmness retention as measured from compression parameters. The increase in firmness with respect to that of unblanched potatoes diminished in the order: blanched at 60 °C for 60 min and cooked > blanched at 60 °C for 60 min frozen and cooked > blanched at 60 °C for 60 min. Potato tubers were kept in refrigerated storage, and firmness, PME activity and dry matter (DM) content were periodically sampled over a period of 80 days. In the early stages of storage, PME activity lost 40% of its original value after 60 min at 60 °C, indicating that the contribution of starch breakdown products to the firmness of cooked and frozen cooked potatoes predominated over the effect of enzyme activity. With increasing time in storage, PME activity measured in the fresh tissue increased by 95% of its original value after 35 days; this resulted in changes in the pectic polymers which made for a firmer texture and different PME behaviour versus LTB temperature and time. A central composite rotatable design was used to study the effects of variation in levels of temperature (52.93–67.07 °C) and time (31.72–88.28 min) on compression parameters and PME activity. Stationary points showing maximum mechanical resistance had critical temperatures and times in the ranges of temperature (58–60 °C) and time (66–75 min) used for each independent variable. Results show a high correlation between PME activity and tissue firmness, suggesting that the contribution of the changes in the composition of the cell wall to the firmness of frozen cooked potatoes increased with increasing time in storage and reached a maximum in the intermediate stages of storage (35 days). Engineering stress (_u) proved to be the most appropriate compression parameter for detecting the firming effect that the PME activity produced on the frozen-cooked potato tissues as a consequence of LTB under these conditions.     

Estimation of the marginal location under a partially linear model with missing responses

In this paper, we consider a semiparametric partially linear regression model where there are missing data in the response. We propose robust Fisher-consistent estimators for the regression parameter, for the regression function and for the marginal location parameter of the response variable. A robust cross-validation method is briefly discussed, although, from our numerical results, the marginal estimators seem not to be sensitive to the bandwidth parameter. Finally, a Monte Carlo study is carried out to compare the performance of the robust proposed estimators among themselves and also with the classical ones, for normal and contaminated samples, under different missing data models. An example based on a real data set is also discussed.     

Text summarization contribution to semantic question answering: New approaches for finding answers on the web

As the Internet grows, it becomes essential to find efficient tools to deal with all the available information. Question answering (QA) and text summarization (TS) research fields focus on presenting the information requested by users in a more concise way. In this paper, the appropriateness and benefits of using summaries in semantic QA are analyzed. For this purpose, a combined approach where a TS component is integrated into a Web‐based semantic QA system is developed. The main goal of this paper is to determine to what extent TS can help semantic QA approaches, when using summaries instead of search engine snippets as the corpus for answering questions. In particular, three issues are analyzed: (i) the appropriateness of query‐focused (QF) summarization rather than generic summarization for the QA task, (ii) the suitable length comparing short and long summaries, and (iii) the benefits of using TS instead of snippets for finding the answers, tested within two semantic QA approaches (named entities and semantic roles). The results obtained show that QF summarization is better than generic (58% improvement), short summaries are better than long (6.3% improvement), and the use of TS within semantic QA improves the performance for both named‐entity‐based (10%) and, especially, semantic‐role‐based QA (47.5%). © 2011 Wiley Periodicals, Inc.     

Parameter tuning of a choice-function based hyperheuristic using Particle Swarm Optimization

A Constraint Satisfaction Problem is defined by a set of variables and a set of constraints, each variable has a nonempty domain of possible values. Each constraint involves some subset of the variables and specifies the allowable combinations of values for that subset. A solution of the problem is defined by an assignment of values to some or all of the variables that does not violate any constraints. To solve an instance, a search tree is created and each node in the tree represents a variable of the instance. The order in which the variables are selected for instantiation changes the form of the search tree and affects the cost of finding a solution. In this paper we explore the use of a Choice Function to dynamically select from a set of variable ordering heuristics the one that best matches the current problem state in order to show an acceptable performance over a wide range of instances. The Choice Function is defined as a weighted sum of process indicators expressing the recent improvement produced by the heuristic recently used. The weights are determined by a Particle Swarm Optimization algorithm in a multilevel approach. We report results where our combination of strategies outperforms the use of individual strategies.     

Oscillatory Rheological Properties of Fresh and Frozen/Thawed Mashed Potatoes as Modified by Different Cryoprotectants

Five different hydrocolloids (amidated low-methoxyl [ALM] and high-methoxyl [HM] pectins, kappa- and iota-carrageenans [κ-C and ι-C], and xanthan gum [XG]) and two dairy proteins (whey protein [WP] and sodium caseinate [SC]) were added at five different concentrations to fresh (F) and frozen/thawed (F/T) mashed potatoes to investigate ways of improving the effects of freezing and thawing. It was found that each hydrocolloid and protein, depending on the concentration, affected the viscoelastic properties of F and F/T mashed potatoes in a different way. Color, drip loss (DL), total soluble solid (TSS) content, and overall acceptability (OA) were also determined. All systems showed weak gel behavior, although the F samples exhibited higher values of G′ and G″ as compared to F/T counterparts. However, the effects were highly dependent on the type and level of biopolymer added. F and F/T mashed potatoes with added WP presented higher values of G′ and G″, and values were lowest in both when XG was added. After freezing and thawing, the addition of ingredients (3 to 5 g kg⁻¹ ALM and HM, 3 to 8 g kg⁻¹ κ-C, and 1.5 g kg⁻¹ WP) had the effect of thickening the mash and thus improving freeze/thaw stability. Processed samples were darker than F samples, although this darkening was not detected by the panelists. Color was affected less by κ-C or ι-C than by the other ingredients added. ALM pectin, κ-C and ι-C, XG, and SC all exhibited water-holding capability, whereas HM and WP did not. The product yielded by XG was softer than controls without added cryoprotectants in both F and F/T samples, but samples containing 0.5 and 1.5 g kg⁻¹ added XG were judged more acceptable than the F control because of the creamy mouth-feel it produced.     

On the glucoside analysis: Simultaneous determination of free and esterified steryl glucosides in olive oil. Detailed analysis of standards as compulsory first step

This work covers two important gaps in the field of micronutrient databases: herein we describe a short and easy protocol that allows the analysis of both free and esterified steryl gulcosides in olive oil. By utilising accurate quantitative methods we achieve a better understanding of olive oil composition and health promoting properties. The procedure consists of isolating the fraction of interest through solid phase extraction, and using gas chromatography–flame ionisation detection for both identification and quantification of the derivatised species. Additionally, mass-spectrometry detection has been utilised for confirming the identity of the individual esterified steryl glucosides in some cases.     

A rheological characterisation of mashed potatoes enriched with soy protein isolate

The effect of the addition of soy protein isolate (SPI) (0, 15, 30, 45 and 60 g kg⁻¹) on viscoelastic properties, large deformation measurements and microstructure of fresh (FM) and frozen/thawed (F/TM) mashed potatoes was investigated. Rheological data showed weak gel behaviour for both FM and F/TM potatoes without and with added SPI together with a significant decrease of system viscoelasticity (G′ and G″) with increasing SPI volume fraction, primarily attributed to the no interaction between the amylose/amylopectine matrix and the dispersed SPI particles or aggregates as revealed by scanning electron microscopy (SEM). Micrographs also showed that SPI formed white coarse aggregates. A freeze/thaw cycle produced a more significant decrease in viscoelastic functions, due to superior aggregation of denatured SPI and reduced water activity. In F/TM samples, high correlations between small and large deformation measurements were found. Results may be useful for technological applications in SPI-enriched mashed potatoes.