Soybean drying in fluidized bed. effect on the hydratable and nonhydratable phosphatide concentration in crude and degummed crude oil

Abstract

The content of nonhydratable phosphatides in soybean crude oil is increased by phospholipase D activity during the oil-making process. Enzyme inhibition would allow to minimize them. Recently harvested soybeans with high moisture levels require adequate drying to store safely. Simultaneous soybean drying and phospholipase D inactivation in a single operation when applying a thermal treatment by the fluidized-bed technique was evaluated. The process conditions for performing the drying and a complete enzyme inhibition on soybeans, with an initial moisture content between 7.4 and 20.6% wet basis, similar to that at the time of the harvest, were fluidizing and drying medium temperature between 110 and 140°C, and a drying time between 1 and 2 min. For the treated soybeans, the phosphorus content increased up to 223% in crude oil and decreased 17% in degummed crude oil with regard to the values of the control sample.The production of refined oil requires phosphatide removal from crude oil (CO). Most soybean CO phosphatides are hydratable (HP) and can be separated by means of aqueous degumming. The increment of nonhydratable phosphatides (NHP) diminishes the degumming efficiency, so it is necessary to use treatments which increase the oil lost (1). Transformation of HP into NHP is carried out during the oil-making process by phospholipase D (PLD) (2), which is freed by cell breakage during cracking and flaking operations (3). Soybean PLD activity increases linearly as temperature increases when the grain moisture content is between 11.3 and 13.6% wet basis (wb), and its greatest activity is at 85°C. NHP content in CO increases at the same time as the extraction temperature (4). List et al. (3,5) proved that moisture, cellular disruption, heat, and PLD activity are factors that promote NHP formation; PLD inactivation minimizes it. PLD was fully inactivated in whole soybeans by a 8-9 min microwave treatment at 115-120°C, and by a live steam treatment at about 110°C of soyflakes. In both cases, it was proved that thermal treatment completely destroyed PLD activity and made moisture removal possible.Kock (4) demostrated by means of a moisture-heat treatment of soyflakes prior to extraction that enzyme activity could be completely eliminated, thereby minimizing NHP formation.To store soybeans safely when their moisture exceeds 14.2% wb, they must be dried while minimizing grain fissuring, cracking, and dehulling. Florin and Bartesch (6) proposed fluidized-bed (FB) for drying, cooling, dehulling, and conditioning in oil seed processing. This method is advantageous for the following reasons: homogeneous product treatment, additional cleaning, precise control of treatment temperature, low quality losses, and low damage levels of oil and proteins.Tosi et al. (7) dried soybeans in a FB and proposed an empirical equation for the drying kinetics. A 3-min FB treatment at 130°C is enough to achieve soybean drying with 17.5% wb initial moisture content and to destroy urease and the trypsin inhibitor simultaneously. The available lysi...

Soybean phospholipase D activity determination. A comparison of two methods

“…Discrepancies in the values of PLD activity (PLDA) arise from comparing the results obtained by List et al (1990List et al ( , 1992 and by Tosi et al (1999). The PLDA found by Tosi et al was 150 times the PLDA found by List et al In their works, List et al (1990, 1992 applied the method of extracting the enzyme from the soybean original matrix according to a modification of the method proposed by Nakayama et al (1981) to extract the PLD from white cabbage.…”

“…On the other hand, Tosi et al (1999) used a method based on the action of the PLD, contained in the soybean original matrix, by mixing up milled soybean with soybean lecithin as substrate. Both authors used the same 270 GRASAS Y ACEITES, 58 (3), JULIO-SEPTIEMBRE, 270-274, 2007, ISSN: PSOYBEAN PHOSPHOLIPASE D ACTIVITY DETERMINATION.…”

“…Briefly, PLDA determination was based on the action of the phospholipase D, either extracted according to List et al (1990List et al ( ,1992, or not extracted but remaining in the original soybean matrix according to Tosi et al (1999), upon soybean lecithin releasing choline (Eq. 1).…”

Recent developments in edible oil processing

“…For the reference oil, a residual phosphorus content of 150 ppm was assumed after water degumming and the phosphatide composition of the NHP is in accordance with [10]. The expander treatment of soya [15,16] and the drying of soya beans in a fluidised bed [17] also lead to more phosphatides in the crude oil but less residual phosphatides in water-degummed soya bean oil and similar observations have been made for rapeseed oil [18].…”

Influence of fluidized‐bed roasting conditions of white sesame seeds on the physico‐chemical properties and sensory acceptability of the cold‐pressed oils

“…Tosi et al. (1999) reported the decrease of nonhydratable phosphatides in soybean crude oil, as a consequence of phospholipase D inactivation by the fluidized‐bed technique. In addition, fluidized‐bed dryers can be found as part of methods for roasting oilseeds such as flaxseed (Werner, 2008).…”