Sensory characteristics and consumer acceptance of frozen cooked rice by a rapid freezing process compared to homemade and aseptic packaged cooked rice

Postprandial Glucose Response after Consuming Low-Carbohydrate, Low-Calorie Rice Cooked in a Carbohydrate-Reducing Rice Cooker

This study evaluates whether blood glucose response differs upon consuming rice cooked in a carbohydrate (carb)-reducing rice cooker. Rice cooked this way exhibited 19% reduced total carbohydrate (34.0 ± 0.3 vs. 27.6 ± 0.9 g/100 g rice) and 20% reduced total calorie (149.0 ± 1.0 vs. 120.8 ± 3.7 kcal/100 g rice) contents. We measured the blood glucose response (at 0, 15, 30, 45, 60, 90, and 120 min) in 13 healthy participants after consuming 6 different rice types: regular white rice (regular WR, 50 g of available carbohydrate (AC)), low-carb WR with equivalent weight as regular WR (low-carb WR (EW)), low-carb WR with equivalent carb as regular WR (low-carb WR (EC), regular mixed-grain rice (regular MR), low-carb MR (EW) as regular MR, and low-carb MR (EC) as regular MR. All rice samples were prepared in an electric carb-reducing rice cooker. Postprandial blood glucose, sensory, and appetite were assessed after each test meal. The incremental area under the curve of 15 and 30 min after rice consumption was significantly lower in low-carb WR (EW) than that in regular WR. These results suggest possible health benefits of low-carb WR in reducing early postprandial spikes in blood glucose level without significant differences in satiety and satisfaction.

Preference mapping of different water-to-rice ratios in cooked aromatic white jasmine rice

The volume of water is a key variable affecting texture and flavor attributes of cooked rice with a significant influence on consumer preference. The aim of this study was to determine the attributes driving consumer preference for rice cooked with different water-to-rice ratios. Descriptive analysis (DA) methodology was employed to profile aromatic white Jasmine rice and a consumer study was run to determine preference for water-to-rice ratios. A DA panel (n = 12) evaluated ten aroma, four taste and flavor, three texture, and six appearance attributes for aromatic white Jasmine rice cooked with four water-to-rice ratios (1.125:1, 1.5:1, 1.875:1, and 2.25:1). Rice consumers (n = 117) evaluated preferences of the same aromatic white Jasmine rice cooked with the aforementioned water-to-rice ratios. DA results revealed floral aroma, firmness, chewiness, coarseness, stickiness/cohesiveness, and fluffiness were significantly influenced by an increasing water-to-rice ratio. There was no significant effect of water-to-rice ratios on consumer preferences (χ² (3, 117) = 1.17; P = 0.76). Consumers were grouped into three clusters with similar preference patterns using agglomerative hierarchical clustering. External preference mapping techniques run on each consumer cluster determined the water-to-rice ratios 1.125:1 and 1.875:1 as having the largest appeal to heavy consumers of rice, split by preferences for fluffy or sticky cooked rice. The water-to-rice ratio 1.5:1 was not dominated by any single attribute or group of attributes, appealing to less frequent rice consumers. Therefore, the water-to-rice ratios 1.125:1, 1.5:1, and 1.875:1 should satisfy the broadest groups of Australian rice consumers. PRACTICAL APPLICATION: Rice, a high volume commodity can be cooked using a variety of methods and volumes of water. The findings of this research will help manufacturers market water-to-rice ratios, assisting consumers in identifying cooked rice for which they have a preference.

Influence of Packaging Oxygen Transmission Rate on Physical Characteristics of Frozen Cooked Rice Under Various Freezing Conditions

The influence of packaging oxygen transmission rate (OTR; 0, 3,000, 5,000, 7,000, and 20,000 [mL/m² ]/day) on cooked rice quality factors, including freezing rate and time, moisture content, color parameters, texture characteristics, and morphology, were evaluated. Cooked rice was frozen at -20 and -80 °C using packaging with different OTRs for 14 days. Freezing rates in packaging with lower OTRs (0, 3,000, and 5,000 [mL/m² ]/day) were higher than those in packaging with higher OTRs. The moisture content of cooked rice was the highest in OTR 5,000 packaging under all experimental conditions. Lightness (L^* ) and total color difference (ΔE) values were the highest in OTR 20,000 packaging, whereas ΔE values were the lowest in OTR 5,000 packaging. Hardness and cohesiveness of frozen cooked rice gradually increased from OTR 0 to 5,000 but decreased from OTR 5,000 to 20,000. Morphology was distinct in all conditions and at all OTRs. Thus, we confirmed that the OTR of packaging influences the physical characteristics of frozen cooked rice. Therefore, packaging OTR should be considered when seeking to improve the quality of frozen cooked rice. PRACTICAL APPLICATION: Packaging oxygen transmission rate (OTR) influenced quality characteristics of frozen cooked rice under various freezing conditions. Cooked rice frozen in packaging with lower OTRs (0, 3,000, and 5,000 [mL/m² ]/day) showed higher freezing rates, higher moisture content, shorter freezing times, smaller ice crystal formation, homogeneous pore distribution, and lower total color differences (ΔE) than did cooked rice frozen in packaging with higher OTRs (7,000 and 20,000 [mL/m² ]/day). Packaging OTR influences frozen cooked rice quality characteristics, and should therefore be carefully considered when designing rice products.

Establishment of comprehensive quality evaluation model of fresh instant rice

Background

Although the rice processing characteristics and processing quality evaluation technologies have been studied for many years in China, there have been few reports on the evaluation index system and evaluation method of fresh instant rice processing quality.

Objective

The aim of this study was to establish a comprehensive quality evaluation model of fresh instant rice to achieve the effective quantitative quality analysis.

Methods

A total of 108 japonica rice varieties were selected as the test samples, followed by the production of fresh instant rice. The color value, physicochemical quality, texture characteristic, and sensory quality of fresh instant rice were systematically analyzed. Difference analysis, correlation analysis, factor analysis, and cluster analysis were used to determine the representative quality indexes of fresh instant rice. Through initialization, forward, and normalization, the standardized indexes (0≤ X_i ≤1) were obtained. The discriminant matrix of the analytic hierarchy process (AHP) was used to confirm the weight (W_i ) of each representative quality index, establishing the comprehensive quality evaluation model.

Results

The variable coefficients of 12 out of 17 quality indexes were more than 10%. There were 136 correlation coefficients, including 15 cases with a significant difference at the level of α = 0.05 and 52 cases with a significant difference at the level of α = 0.01. Five representative quality indexes of fresh instant rice were selected by factor analysis and cluster analysis, including palatability, adhesiveness, b* value, resilience, and iodine color value. And the comprehensive quality evaluation model of fresh instant rice integrating representative indexes was obtained: Y = 0.5650 × palatability + 0.2294 × adhesiveness + 0.0328 × resilience + 0.1175 × b* value + 0.0533 × iodine color value.

Conclusion

The AHP combined with factor analysis and cluster analysis can convert a number of quality indexes into a comprehensive quality index, and thus establish the comprehensive quality evaluation model of fresh instant rice, effectively performing the quantitative quality analysis. This model not only provided a scientific basis for the accurate evaluation of fresh instant rice quality, but also laid the foundation for the formulation of fresh instant rice standards in the future.

6-(2-Formyl-5-methyl-1H-pyrrol-1-yl)hexanoic Acid as a Novel Retronasal Burnt Aroma Compound in Soy Sauce Aroma-Type Chinese Baijiu

Two-step high-performance liquid chromatography (HPLC) separation in combination with taste dilution analysis was used to screen the retronasal burnt aroma compounds in soy sauce aroma-type Chinese Baijiu (Chinese traditional liquor). A major retronasal burnt aroma region was purified by Sephadex LH-20 column chromatography and HPLC separation from the soy sauce aroma-type Baijiu sample. A novel retronasal burnt aroma compound was identified as 6-(2-formyl-5-methyl-1H-pyrrol-1-yl)hexanoic acid (1) by means of high-resolution mass spectrometry and 1D/2D nuclear magnetic resonance. The retronasal burnt aroma threshold of compound 1 was determined to be 209.5 μg/L in 53% ethanol aqueous solution. Quantitative analysis showed that the concentration of compound 1 ranged from below the limit of quantitation (3.8 μg/L) to 224.2 μg/L in the Baijiu samples. Moreover, the sensory evaluation also revealed that compound 1 may contribute to the retronasal burnt aroma of the Baijiu at its subthreshold concentration by the additive effect with the recently reported retronasal burnt aroma compound 2-hydroxymethyl-3,6-diethyl-5-methylpyrazine.

Identification of 2-Hydroxymethyl-3,6-diethyl-5-methylpyrazine as a Key Retronasal Burnt Flavor Compound in Soy Sauce Aroma Type Baijiu Using Sensory-Guided Isolation Assisted by Multivariate Data Analysis

The burnt flavor (overcooked rice flavor) is often retronasally perceived during the soy sauce aroma type Chinese Baijiu (Chinese distilled spirit) tasting and regarded as an important quality marker of the Baijiu. The sensory-guided isolation approach assisted by multivariate data analysis was applied to identify the compounds responsible for the retronasal burnt flavor in the Baijiu. Using two-dimensional offline high performance liquid chromatography separation and taste dilution analysis, a subfraction with the highest burnt flavor intensity was isolated from the Baijiu sample. In the subfraction, six potential flavor compounds were detected by ultra performance liquid chromatography-mass spectrometry. The most probable burnt flavor compound was screened by projection to latent structure regression analysis of the correlation between the potential compounds and their impact on burnt flavor. The target compound was identified as 2-hydroxymethyl-3,6-diethyl-5-methylpyrazine by means of high-resolution mass spectrometry and chemical synthesis. Sensory evaluation revealed a relatively low burnt flavor threshold of 2.89 μmol/L in 53% ethanol aqueous solution. On the basis of the dose-overthreshold factor and addition experiment, this compound was confirmed as the key contributor to the burnt flavor of soy sauce aroma type Baijiu.

Effects of ripening temperature on starch structure and gelatinization, pasting, and cooking properties in rice (Oryza sativa)

The effect of ripening temperature on rice (Oryza sativa) grain quality was evaluated by assessing starch structure and gelatinization, pasting, and cooking properties. As the ripening temperature increased, the amylose content and number of short amylopectin chains decreased, whereas intermediate amylopectin chains increased, resulting in higher gelatinization temperatures and enthalpy in the starch. These results suggested that an increase in cooking temperature and time would be required for rice grown at higher temperatures. A high ripening temperature increased the peak, trough, and final viscosities and decreased the setback due to the reduction in amylose and the increase in long amylopectin chains. With regard to starch crystallinity and amylopectin molecular structure, the highest branches and compactness were observed at 28/20 °C. Rice that was grown at temperatures above 28/20 °C showed a deterioration of cooking quality and a tendency toward decreased palatability in sensory tests.