/pdf/lipase-and-lipoxygenase-activity-functionality-and-nutrient-22alufdkzn.pdf

Lipase and Lipoxygenase Activity, Functionality, And Nutrient Losses in Rice Bran During Storage

Effect of various heat treatments on rancidity and some bioactive compounds of rice bran

The purpose of this research was to develop a simple method for measuring lipase activity as an indicator of wheat and wheat bran storage quality. This simplified method does not require the separation or purification of lipase. Optimal conditions for lipase activity measurements were determined by varying the substrate (olive oil) and water concentrations, temperature, and incubation time. Following incubation, FFA were quantified spectrophtometrically using a copper soap assay, and lipase activity was expressed as units/gram (U/g), where 1 U was defined as the microequivalents of oleic acid liberated per hour. The method was tested on one commercial and four pure wheat cultivars. The lipase activity was also correlated with the development of FFA during actual storage of heat-treated commercial bran. Lipase activity in wheat bran ranged from 2.17 to 9.42 U/g, and in whole kernel wheat from 1.05 to 3.54 U/g. Optimal olive oil and water concentrations were 0.4 to 0.8 mL and 0.15 to 0.20 mL per g of defatted sample, respectively. Optimal incubation temperature was 40°C, and incubation times of up to 8 h were linear. Lipase activity was highly correlated with the buildup of FFA in stored wheat bran (R2=0.97).

A simple method to measure lipase activity in wheat and wheat bran as an estimation of storage quality

The purpose of this study was to determine the effectiveness of dry heat, steam, and microwave treatments in decreasing lipase activity, while retaining antioxidant activity, to stabilize whole wheat flour against lipid degradation during storage. Bran was heat-treated in 230-g batches using four levels (exposure times) for each of the three treatment methods. Lipase activity and antioxidant activity were quantified for all treatment combinations. None of the treatments significantly decreased antioxidant activity; the levels determined to be optimal, inasmuch as further heating did not significantly decrease lipase activity, were 25 min of dry heat, 60 sec of microwave (1000W), and 60 sec of steam. These treatments effectively decreased lipase activity by 74, 93, and 96%, respectively. Optimum treatments were evaluated for acceptance using a consumer sensory panel during a 12-month storage period. No significant differences in acceptance were found between the control and any of the samples eith...

/pdf/enhanced-lipid-stability-in-whole-wheat-flour-by-lipase-2brq2wx1qp.pdf

Enhanced Lipid Stability in Whole Wheat Flour by Lipase Inactivation and Antioxidant Retention

Cereal grains have represented the principal component of the human diet for thousands of years. Their processing comprises an important part of the food production chain, but it is a complex procedure. The most common cereal processes include dry milling (wheat and rye), pearling (rice, oat, and barley), wet milling (corn and wheat), and malting (barley, corn, and wheat). During cereal processing, by-products that differ in their physical state and chemical composition are coproduced. Since cereals are an important source of carbohydrates, proteins, lipids, vitamins, mainly of B-complex and vitamin E, and inorganic and trace elements, the reutilization and valorization of their by-products is a great challenge toward the sustainable development of the agrofood sector. This chapter provides an introduction to cereal production processes and their corresponding by-products.

E. T. Champagne

Papers

Stabilizing brown rice to lipolytic hydrolysis by ethanol vapors