Relationships of Overall Estery Aroma Character in Lagers with Volatile Headspace Congener Concentrations

In lager beers the intensity of “estery” aroma character is regarded as an important component of sensory quality, but its origins are somewhat uncertain. Overall “estery” aroma intensity was predicted from capillary gas chromatographic (GC) data following solid phase micro extraction (SPME) of headspaces. Estery character was scored in 23 commercial lagers using rankrating, allowing assessors (13) constant access to a range of appropriate standards. From univariate data analysis, all assessors behaved similarly and lagers fell into three significantly different groups: low (1), high (1) and intermediate (21). The quantification of 36 flavour volatiles by SPME of headspaces was reproducible and principal component analysis explained 91% total variance. Multiple linear regression could utilise only a restricted (26) set of flavour volatiles, whereas partial least square regression, that considered all flavour components, showed significant differences and improved prediction. However, an artificial neural network that could compensate for non‐linearities and interactions in ester perception gave the most robust prediction at R² = 0.88.     

Staling in Two Canned Lager Beers Stored at Different Temperatures — Sensory Analyses and Consumer Ranking

Two canned lagers, lager A (5% abv with late hop character) and lager B (4% abv) stored for 0, 7, 14, 21 and 28 days at 4, 12, 30 and 37°C were scored by trained sensory assessors (10) for liking and stale and related attributes of: cabbagy, cardboard, catty, grainy, honey, leathery, metallic, musty, skunky, and sour. Principal component analysis explained 80% data variance in 3 significant (p < 0.05) and 75% in 4 significant factors for A and B, respectively. In both lagers, aging correlated significantly with stale, cabbagy and musty and in A with metallic and sour and in B with catty and skunky. Partial least squares regression (PLS1) models showed good explanations: stale had regression coefficients of 0.88 (calibration) and 0.84 (validation) for A, and 0.96 and 0.91 respectively, for B; for liking 0.92 and 0.90 for A and 0.96 and 0.93 for B. For both lagers, liking was positively correlated with honey and grainy, and inversely with staling attributes. Lagers from 30°C were ranked for liking by 40 consumers against fresh as a hidden reference. Significant (p = 0.05) ranking of A, but not B, correlated with that of trained assessors.     

2‐Furoylmethyl amino acids,hydroxymethylfurfural, carbohydrates and β‐carotene as quality markers of dehydrated carrots

BACKGROUND: Processing of vegetables in the food industry usually includes dehydration as a preservation process. Industrial convective air drying of carrot can involve steam blanching of the raw product after peeling and cutting, and different stages of dehydration (first space, second space and final drying). Although the shelf‐life of carrot is significantly extended, important changes in its chemical composition can take place during dehydration since high temperatures and long times are used. This research is a preliminary study to evaluate the usefulness of β‐carotene, carbohydrates, hydroxymethylfurfural (HMF) and 2‐furoylmethyl amino acids (2‐FM‐AA) as quality markers of dehydrated carrots. RESULTS: A considerable decrease in β‐carotene and reducing carbohydrates was observed during dehydration. HMF, absent in raw carrots, increased during the whole drying process and the highest formation was found during the steam blanching stage. 2‐FM‐AA of lysine, arginine, γ‐aminobutyric acid and alanine were progressively originated up to the second space and decreased during the final drying. CONCLUSION: The combined use of HMF and 2‐FM‐AA seems to be advantageous for the assessment of the optimal processing conditions to obtain high‐quality dehydrated carrots. Copyright © 2008 Society of Chemical Industry     

Optimization of Operating Conditions in Rice Heat Blast Process for Chinese Rice Wine Production by Combinational Utilization of Neural Network and Genetic Algorithms

The rice heat blast process is a novel technique for gelatinizing raw starch. It uses heated air to replace steam for processing rice under high temperature fluidization in a short time period. This is a new technique for making rice wine with the characteristics of easy storage and zero water pollution. This study focused on three major performance indexes (starch gelatinization ratio, total fat content, and amino nitrogen content in the roasted rice), which largely affect the performance of the rice heat blast process and the rice wine quality. The relationship between these performance indexes and the corresponding operation variables were modeled by an artificial neural network (ANN) via learning sets of experimental data. Based on the ANN models obtained, genetic algorithms were used to optimize the operating conditions of the rice heat blast process. The results showed the power in determination of optimal operating conditions by the combinational utilization of artificial neural network and genetic algorithms.     

Effect of nano‐TiO2‐LDPE packaging on microbiological and physicochemical quality of Pacific white shrimp during chilled storage

Nano‐TiO₂‐modified low‐density polyethylene (NTLDPE) packaging was prepared by blending LDPE with nano‐TiO₂. The effects of NTLDPE packaging on quality of Pacific white shrimp during storage at 4 °C were investigated. Results showed that NTLDPE lowered the K value by 28.50%, while increased sensory score by 30.77% in comparison with the control. NTLDPE packaging retarded the decrease of whiteness and water holding capacity and the increase of melanosis score based on the signs of freshness and deterioration of shrimp. Furthermore, NTLDPE packaging reduced total viable counts (TVC) by 6.42% and total volatile basic nitrogen (TVB‐N) contents were 14.82% lower than that of control. TVB‐N content and TBARS value, as well as polyphenol oxidase activity and TVC, were maintained and shrimp remained a commercial acceptability for 8 days. The overall results indicated that NTLDPE packaging could preserve the quality and extend the shelf‐life of Pacific white shrimp.     

Pre‐harvest calcium treatments in relation to the respiration rate and ethylene production of ‘Golden Smoothee’ apples

Multivariate procedures were used to evaluate the effect of different pre‐harvest calcium treatments on the changes of respiratory rate and ethylene production in apples both at harvest and after extended cold storage. The study was carried out over two years on ‘Golden Smoothee’ apple trees from Lleida (Spain). Trees were sprayed with a calcium chloride based formulation (STOPIT) at a concentration of 1% (v/v). The first (6 applications) and second (12 applications) treatments began 60 days after full bloom (DAFB) and were repeated at intervals of 15 and 7 days respectively. After harvesting, the fruit was stored for 4 and 6 months under controlled ultra‐low oxygen atmosphere conditions (CA‐ULO). Each time fruit was withdrawn from storage, carbon dioxide and ethylene production were measured for 14 days at 20 °C. Independently of the calcium treatments, respiration rates fell from harvesting until 6 months of storage, while ethylene production was greater on withdrawal from storage than at harvest. Respiratory rate and ethylene production correlated negatively with calcium content. However, calcium apparently had a greater effect on the respiratory capacity (CO₂) of fruit than on ethylene production. Copyright © 2004 Society of Chemical Industry     

Inhibition of 2‐Amino‐1‐methyl‐6‐phenylimidazo [4,5‐b]pyridine (PhIP) Formation by Alkoxy Radical Scavenging of Flavonoids and Their Quantitative Structure–Activity Relationship in a Model System

The inhibitory effect of 10 flavonoids on the formation of 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) in a creatinine–phenylalanine model system was investigated through electronic spin resonance and a quantitative structure–activity relationship. Alkoxy radicals were observed during the heating process, providing evidence for a radical pathway in the formation of PhIP. The alkoxy radical scavenging capability of the flavonoids was proportional to their inhibition of PhIP formation (IC₅₀). We deduced that flavonoid inhibition of PhIP generation occurs via scavenging of alkoxy radicals during the heating process. Multiple linear regression and partial least squares models were used to elucidate the relationship between PhIP inhibition activity and structure characteristics of the flavonoids. The lipo–hydro partition coefficient and molecular fractional polar surface area of the flavonoids were found to be predictive of the inhibition effect.     

Determining degree of roasting in cocoa beans by artificial neural network (ANN)‐based electronic nose system and gas chromatography/mass spectrometry (GC/MS)

BACKGROUND

Roasting is a critical step in chocolate processing, where moisture content is decreased and unique flavors and texture are developed. The determination of the degree of roasting in cocoa beans is important to ensure the quality of chocolate. Determining the degree of roasting relies on human specialists or sophisticated chemical analyses that are inaccessible to small manufacturers and farmers. In this study, an electronic nose system was constructed consisting of an array of gas sensors and used to detect volatiles emanating from cocoa beans roasted for 0, 20, 30 and 40 min. The several signals were used to train a three‐layer artificial neural network (ANN). Headspace samples were also analyzed by gas chromatography/mass spectrometry (GC/MS), with 23 select volatiles used to train a separate ANN.

RESULTS

Both ANNs were used to predict the degree of roasting of cocoa beans. The electronic nose had a prediction accuracy of 94.4% using signals from sensors TGS 813, 826, 822, 830, 830, 2620, 2602 and 2610. In comparison, the GC/MS predicted the degree of roasting with an accuracy of 95.8%.

CONCLUSION

The electronic nose system is able to predict the extent of roasting, as well as a more sophisticated approach using GC/MS. © 2018 Society of Chemical Industry     

A Reappraisal of the Differences Between Scandinavian and Spanish Barleys: Effect of β‐Glucan Content and Degradation on Malt Extract Yield in the cv. Scarlett

Forty one samples of the malting barley cultivar Scarlett were collected from both Scandinavia (15 from Finland and 10 from Denmark) and the Iberian Peninsula (15 from Spain and 1 from Portugal), during the harvest years of 1998 and 1999. These samples were subjected to grain analyses, comprising protein content, hordein fractions by high performance liquid chromatography (HPLC) and β‐glucan content. The samples were micro‐malted and the malts were analysed to determine different patterns in the influence of grain composition on malt extract development linked to the two contrasting environments. The most obvious difference found between the Scandinavian and Iberian barleys was the effect of the total and insoluble barley β‐glucans. They were an effective barrier of malt extract in the North, but appeared to increase extract in the South. A conclusion was that the positive effect of β‐glucans in the Iberian barleys was a consequence of their greater capacity to synthesise and release β‐glucan hydrolases during germination.     

Evaluation of a Modified pH‐Shift Process to Reduce 2‐Methylisoborneol and Geosmin in Spiked Catfish and Produce a Consumer Acceptable Fried Catfish Nugget‐Like Product

Abstract: Muddy and/or musty off‐flavors in farmed‐raised catfish occur as a result of the absorption of geosmin (GEO) and 2‐methylisoborneol (MIB), compounds produced by algae. Previous research suggests the acid pH‐shift method may be able to reduce off‐flavors to produce a consumer acceptable product. The objective of this research was to evaluate application of the acid pH‐shift method using a shaker sieve for protein recovery and to evaluate consumer acceptability of a resultant batter‐coated fried nugget‐like catfish product. Farm‐raised catfish were either allowed to depurate (control) or treated with 1 ppb GEO or MIB. Fillets from each replicate were collected and ground and treated by the acid pH‐shift process. Samples from all treatments and replicates were evaluated for residual GEO and MIB. In addition, batter‐coated fried catfish samples were prepared for a consumer sensory evaluation. Results demonstrated that the pH‐shift process decreased moisture, ash, and collagen content of catfish fillet tissue (P < 0.05). Flavor of control samples was preferred (P < 0.05). Texture of catfish samples treated by the pH‐shift process was preferred (P < 0.05). Results demonstrate the pH‐shift process can be utilized to reduce off‐flavors and increase the acceptability of a processed catfish product. Practical Application: Use of a sieve as an economic alternative for the pH‐shift process was evaluated for removing off‐flavors from catfish. Difficulties were encountered with regard to protein recovery using the sieve and suggestions are made to, perhaps, make the process more applicable for a sieve‐based recovery step. The process as described reduced off‐flavors, but only 2‐fold suggesting the process would work best on catfish near or just over off‐flavor thresholds. Results also indicated the pH‐shift process could be used to improve texture of a fried catfish product designed to be similar to chicken nuggets.     

Quantification of uncertainty using Bayesian and bootstrap models to simulate the impact of nitrogen fertilisation on β‐glucan levels in barley

BACKGROUND: β‐Glucans have enjoyed renewed interest as a functional food ingredient, with current attention focused on optimising β‐glucan levels in finished products without compromising final product quality. In order to measure the uncertainty about the level of β‐glucans in barley, two different statistical methods (Bayesian inference and Bootstrap technique) were applied to measured levels of β‐glucan in three different varieties of barley grain (n = 83). RESULTS: The resulting probability density distributions were similar for the full data set and also when applied to smaller sample sizes, highlighting the potential for either method in quantifying the total uncertainty in β‐glucan levels. Bayesian inference was used to model the effect of nitrogen treatment on β‐glucan and protein contents in barley. The model found that a low level of fertilisation (50 kg N ha^?1) did not have a significant effect on β‐glucan or protein content. However, fertilisation above this level did result in an increase in β‐glucan and protein levels, the effect seeming to plateau at 100 kg N ha^?1. In addition, the uncertainty distributions were significantly different for two consecutive years of data, highlighting the potential environmental influence on β‐glucan content. CONCLUSION: The model developed in this study could be a useful tool for processors to quantify the uncertainty about the initial level of β‐glucan in barley and to evaluate the influence of environmental factors, thus enabling them to formulate their ingredient base to optimise levels of β‐glucan without compromising final product quality. Copyright © 2009 Society of Chemical Industry