Rheological properties of indica rice determined by starch structure related enzymatic activities during after-ripening.

The processing quality of indica rice must undergo ripening after harvest to achieve stability and improvement. However, the mechanism underlying this process remains incompletely elucidated. Starch, the predominant component in indica rice, plays a crucial role in determining its properties. This study focused on analyzing the rheological properties and starch fine structure, as well as the related biosynthetic enzymes of indica rice during the after-ripening process. The results showed that after-ripened rice exhibited increased elastic modulus (G') and viscous modulus (G″), accompanied by a decrease in the loss tangent (Tan δ), indicating an enhancement in viscoelasticity and the gel network structure. Moreover, the proportions of amylopectin super long chains (DP 37-60) decreased, while those of medium chains (DP 13-24 and DP 25-36) or short chains (DP 6-12) of amylopectin increased. Additionally, the activities of starch branching enzyme (SBE) and starch debranching enzyme (DBE) declined over the after-ripening period. Pearson correlation analysis revealed that the rheological properties of after-ripened rice were correlated with the chain length distribution (CLD) of starch, which, in turn, was associated with its related endogenous enzymes. These findings provied new insights into understanding the quality changes of after-ripened indica rice.

Covalent Adduct Formation between ß-Lactoglobulin and Flavor Compounds under Thermal Treatments That Mimic Food Pasteurization or Sterilization.

Thermal processing (e.g., pasteurization and sterilization) is a critical step ensuring the microbial safety of our foods. Previous work from our laboratory has examined the covalent reactions occurring between proteins and a broad selection of flavor compounds under ambient storage temperatures (25-45 °C). However, similar research on reactions of flavor compounds with a protein under thermal processing conditions has not been investigated. In the current study, covalent adduct formation between ß-lactoglobulin (BLG) and 46 flavor compounds encompassing 13 different classes of functional groups was investigated under pasteurization and sterilization conditions by UPLC-ESI-QTOF-MS. BLG was chosen as a representative protein for this study because it is structurally well characterized, its molecular weight is well suited for ESI-MS analysis (18.2 kDa), and it is broadly used in the food industry. Schiff base, aza-Michael addition, and disulfide linkages were the main types of covalent interactions occurring across the reactive samples. Among them, isothiocyanates, aldehydes, and thiol-containing compounds were generally very reactive. Increasing the severity of the thermal treatment [high-temperature-short-time (HTST) pasteurization, in-container pasteurization (IC), and ultra-high-temperature (UHT) sterilization conditions] accelerated the reactions of BLG with flavor compounds, which revealed reactivity of three flavor compounds not previously observed to react at room temperature (eugenol, 4-vinyl phenol, and 3-nonen-2-one). Ketones [other than 2-hydroxy-3-methyl-2-cyclopenten-1-one (cyclotene), diketones, and unsaturated ketones], alcohols, acids, alkenes (terpenes), esters, lactones, 3-acetylpyridine, methyl anthranilate, vanillin, 2-methylthiophene, and dimethyl sulfone did not show measurable reactivity with BLG under the thermal processing conditions examined. An overall view of the data shows that the HTST heat treatment (72 °C for 15 s) had the least effect on the extent of reaction while in-container pasteurization conditions (63 °C for 30 min) produced a similar extent of reaction as the UHT (130 °C 30 s) heat treatment. These varying extents of adductation are in reasonable accord with what one might expect, given that the rates of most classes of chemical reactions occurring near ambient temperature increase by a factor of 2-4 for each increase of 10 K in temperature. Unfortunately, our methodology did not permit us to obtain meaningful data using the most aggressive standard sterilization thermal conditions (110 °C for 30 min) because extensive aggregation/coagulation removed essentially all of the BLG protein from the reaction mixtures prior to MS analysis.

Fingerprinting triacylglycerols and aldehydes as identity and thermal stability indicators of camellia oil through chemometric comparison with olive oil.

Camellia oil is widely recognized as a high-quality culinary oil in East Asia for its organoleptic and health-promoting properties, but its chemical composition and thermal stability have not been comprehensively defined by comparisons with other oils. In this study, the triacylglycerols (TAGs) in camellia, olive, and six other edible oils were profiled by the liquid chromatography-mass spectrometry (LC-MS)-based chemometric analysis. Besides observing the similarity between camellia oil and olive oil, TAG profiling showed that OOO, POO, and OOG (O: oleic acid, P: palmitic acid, and G: gadoleic acid) can jointly serve as the identity markers of camellia oil. Thermal stability of virgin camellia oil (VCO) was further evaluated by extensive comparisons with virgin olive oil (VOO) in common lipid oxidation indicators, aldehyde production, and antioxidant and pro-oxidant contents. The results showed that p-anisidine value (AnV) was the sensitive lipid oxidation indicator, and C9-C11 aldehydes, including nonanal, 2-decenal, 2,4-decadienal, and 2-undecenal, were the most abundant aldehydes in heated VCO and VOO. Under the frying temperature, heated VCO had lower AnV and less aldehydes than heated VOO. Interestedly, the VCO had lower levels of pro-oxidant components, including α-linolenic acid, free fatty acids, and transition metals, as well as lower levels of antioxidants, including α-tocopherol and phenolics, than the VOO. Overall, great similarities and subtle differences in TAG and aldehyde profiles were observed between camellia and olive oils, and the thermal stability of camellia oil might be more dependent on the balance among its unsaturation level, pro-oxidant, and antioxidant components than a single factor.

Identification of C9-C11 unsaturated aldehydes as prediction markers of growth and feed intake for non-ruminant animals fed oxidized soybean oil.

BACKGROUND: The benefits of using the oxidized oils from rendering and recycling as an economic source of lipids and energy in animal feed always coexist with the concerns that diverse degradation products in these oxidized oils can negatively affect animal health and performance. Therefore, the quality markers that predict growth performance could be useful when feeding oxidized oils to non-ruminants. However, the correlations between growth performance and chemical profiles of oxidized oils have not been well examined. In this study, six thermally oxidized soybean oils (OSOs) with a wide range of quality measures were prepared under different processing temperatures and processing durations, including 45 °C-336 h; 67.5 °C-168 h; 90 °C-84 h; 135 °C-42 h; 180 °C-21 h; and 225 °C-10.5 h. Broilers and nursery pigs were randomly assigned to diets containing either unheated control soybean oil or one of six OSOs. Animal performance was determined by measuring body weight gain, feed intake, and gain to feed ratio. The chemical profiles of OSOs were first evaluated by common indicative tests, including peroxide value, thiobarbituric acid reactive substances, p-anisidine value, free fatty acids, oxidized fatty acids, unsaponifiable matter, insoluble impurities, and moisture, and then analyzed by the liquid chromatography-mass spectrometry-based chemometric analysis. RESULTS: Among common quality indicators, p-anisidine value (AnV), which reflects the level of carbonyl compounds, had the greatest inverse correlation with the growth performance of both broilers and pigs, followed by free fatty acids and oxidized fatty acids. Among the 17 aldehydes identified in OSOs, C9-C11 alkenals, especially 2-decenal and 2-undecenal, had stronger inverse correlations (r < - 0.8) with animal performance compared to C5-C8 saturated alkanals, suggesting that chain length and unsaturation level affect the toxicity of aldehydes. CONCLUSIONS: As the major lipid oxidation products contributing to the AnV, individual C9-C11 unsaturated aldehydes in heavily-oxidized oils could function as effective prediction markers of growth and feed intake in feeding non-ruminants.