Nonhydratable Phosphatides Research Articles

Questions begging for answers (Part II) – Refining

Several aspects of the alkali refining process are poorly understood. It is not clear whether or not oil is saponified, and by what mechanism non‐hydratable phosphatides (NHP) are removed from the oil. There is no systematic study on the loss of neutral oil that is entrained by the soapstock and how to minimise this loss and the possible oil loss by hydrolysis during deodorisation or steam refining is not clear either. Some fairly simple experiments will be suggested that might hopefully provide the answers.

Optimization of magnetic immobilized phospholipase A1 degumming process for soybean oil using response surface methodology

This study focused on optimization of processing conditions of enzymatic degumming process for soybean oil using phospholipase A1 immobilized onto magnetic nanoparticles. A response surface methodology was developed and used to obtain optimum processing conditions. Four variables (temperature, reaction time, enzyme dosage, and added water) were investigated based on two response functions (phosphorus and free fatty acids (FFA) contents in degummed soy oil). For each response, second-order polynomial models were developed using multiple linear regression analysis. The optimum operating parameters of enzymatic degumming process were as follows: temperature of 56 °C, reaction time of 6.3 h, enzyme dosage of 0.10 g/kg, and added water of 2.13 ml/100 g. According to these optimum conditions, final residual phosphorus and FFA contents of degummed soy oil were reduced, respectively, to 10.38 mg/kg and 1.09/100 g using magnetic immobilized phospholipase A1. This finding is applicable for the physical refining of soybean oil or refining crude oils from field- and frost-damaged beans which have high content of non-hydratable phosphatides.

Artificial Neural Network or Common Sense Based on Insight?

Dear Sir, In the November issue of JAOCS, you published an article [1] on the use of an artificial neural network for process optimization. I started reading this article with great interest and out of curiosity about this process investigation technique, which, as far as I am aware, has not been the subject of any article in this journal before. However, I soon realized that the authors lacked insight into the chemistry of the degumming process, as a result of which the model the authors propose has little to offer and is even misleading. The combined degumming and bleaching process of palm oil studied by the authors is commonly referred to as the ‘‘dry degumming process’’ [2, 3]. It involves a decomposition of the non-hydratable phosphatides (NHP) present in the oil by phosphoric acid, followed by a bleaching earth treatment. It is very suitable for oils and fats with low NHPcontent (palm oil, lauric oils and animal fats) and has the advantage that it reduces the number of refining steps to only two: dry degumming and physical refining. When summarizing their process, the authors mention that the amount of phosphoric acid used in Malaysian industrial palm oil refineries varies between 0.5 to 1.0 wt% of crude palm oil, and that the amount of bleaching earth varies between 1.0 to 2.0 wt%. In this respect, they disagree with a presentation at a recent short course [4], where 0.1 and 0.07 wt%, respectively, were reported. The authors provide a flow diagram of the combined process (Fig. 1).This flow diagram shows that the phosphoric acid is mixed with an unspecified fraction of the crude palm oil, and that the bleaching earth is mixed with the remainder. Subsequently, the oil stream containing the phosphoric acid and the oil stream containing the bleaching earth are both fed into a degumming and bleaching vessel. The temperature in this vessel is 100 C, the pressure 7 kPa, and the contact time in the batch process is 30 min. The strength of the phosphoric acid and the type of mixer used to disperse the phosphoric acid in the oil are not mentioned. Adding phosphoric acid to only part of the oil completely negates its role in degumming: the decomposition of NHP. For the phosphoric acid to react with as large a fraction of the NHP present as possible, a number of conditions must be met:

Enzymatic degumming

AbstractThe oldest enzymatic degumming process (the Lurgi EnzyMax® process) was launched in 1992. It used porcine phospholipase A2, which has the disadvantages of limited availability and not being kosher/halal. To overcome these disadvantages, various microbial enzymes have been developed; they have different specificities and therefore offer different advantages. Phospholipase C for instance has the advantage that it leads to the formation of diacylglycerols that remain in the oil being degummed. This constitutes a significant yield improvement which also results from the formation of lysophospholipids that retain less oil than their precursors. In the laboratory, a fine dispersion of the aqueous enzyme solution in the oil can be maintained so that the phospholipase enzymes can be made to interact with non‐hydratable phosphatides (NHP) in the oil phase and catalyse their hydrolysis. On an industrial scale, dispersions coalesce before the enzymatic NHP hydrolysis is complete. Accordingly, enzymatic degumming processes that claim NHP‐removal and a low residual phosphorus content in the enzymatically degummed oil are invariably preceded by an acid treatment in which a degumming acid (citric acid) is finely dispersed into the oil to be degummed and made to react with the NHP present in the oil before the enzyme is added. This enzyme then only interacts with the phospholipids present in the water phase. This raises the question whether the yield increase resulting from the use of enzymes should be realised by treating the oil to be degummed or the gums that have already been isolated from the oil during a degumming treatment. Lack of experimental evidence prevents a firm answer to this question but the arguments in favour of treating the gums look more impressive than what can be said in favour of treating the oil. In short: Enzymes do not degum the oil but can be used to de‐oil the gums.

A novel process for physically refining rice bran oil through simultaneous degumming and dewaxing

AbstractA new process for the physical refining of rice bran oil through combined degumming and dewaxing was developed on a laboratory scale and then demonstrated on a commercial scale. The simultaneous degumming and dewaxing of the crude oil with a solution of water and CaCl2, followed by crystallization at a low temperature (20°C), facilitated precipitation of the hydratable and nonhydratable phosphatides along with the wax, which enabled its separation and reduction to a greater extent. Bleaching and subsequent winterization (20°C) of this oil further reduced the phosphorus content to less than 5 ppm. Thus, these pretreatment steps enabled the physically refined rice bran oil to meet commercially acceptable levels for color, FFA content, and cloud point values (10–12 Lovibond units in a 1‐in, cell, <0.25%, and 4–5°C, respectively) with very low neutral oil loss; this has not been observed hitherto. Rice bran oil is known for its high levels of bioactive phytochemicals, such as oryzanol, tocols, and sterols. The process reported here could retain more than 80% of these micronutrients in the end product.

Phosphatides content in soybean oil in function of bean moisture content-at-harvest and storage-time

The influence of soybean moisture content-at-harvest and storage time upon total and non-hydratable phosphatides content in oil and bean phospholipase D activity was evaluated. Tests were performed upon soybeans harvested with moisture contents between 14.4 and 33.3% weight wet basis (wb). They were air dried at 25oC until achieving safe storage moisture contents between 12.8 and 13.5 % wb and were stored at the same temperature for 245 days. Periodically they were analyzed for total and non-hydratable phosphatides content and phospholipase D activity. Total phosphatides initial content was high in soybeans with higher initial moisture levels and decreased slightly with time. Total phosphatides content remained constant at their initial levels in soybeans with lower initial moisture content. Non-hydratable phosphatides content was related to the phospholipase D activity, which decreased 30–35 days after harvest, and then stabilized, with values between 3.0 x 10 -4 and 3.8 x 10 -4 choline mmol/(min • soybean g).

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

AbstractThe 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.

Changes in phospholipase D experession in soybeans during seed development and germination

AbstractActivation of phospholipase D (PLD) has been linked to accumulation of nonhydratable phosphatides and lipid degradation leading to soybean seed deterioration during preharvest and postharvest events. This study examined the changes in PLD activity, protein, and mRNA in soybeans during seed development and germination. RNA blotting analysis indicated that expression of the gene that encodes PLD was highest during the early and middle stages of seed development. However, the amount of PLD activity accumulated per cotyledon reached the highest level in mature seeds. During germination and early seedling growth, PLD mRNA was not detected one day after imbibition, while a significant increase in PLD expression occurred in the cotyledons of three‐ and seven‐day seedlings. Similarly, PLD activity and protein concentration showed little change during the first day of imbibition and increased afterward in three‐ and seven‐day seedlings. These results suggested that expression of PLD is developmentally regulated and that the changes in its amount of activity and protein are controlled primarily at the mRNA level. Immunoblotting analysis further revealed the presence of PLD variants that were associated with specific stages of seed development and seedling growth. The PLD variants present in the cotyledons of mature seeds appeared to be distinct from those observed in the early stage of seed development and in young seedlings.

Degumming soybean oil from fresh and damaged beans with surface‐active compounds

AbstractOils from both properly stored and damaged soybeans were degummed with a series of 4 nonionic, 2 cationic and 5 anionic surfactants and with lecithins as amphoteric emulsifiers. Efficiency of phosphatide removal in the presence or absence of citric acid was determined by colorimetric analysis of phosphorus in the degummed oils. For normal oils, efficiency of citric acid degumming was improved by the addition of fatty alkyl oxazoline, polymeric sulfonate, alkyl sulfate and crude or purified lecithin. Success in degumming of oils from partially damaged soybeans was limited; however, the average phosphorus content was lowest for those solutions degummed with alkyl sulfate. Aqueous citric acid degumming of oils from severely damaged soybeans indicated high levels of nonhydratable phosphatides (NHP). When added to the oil from severely damaged beans, several nonionic and anionic surfactants showed statistically significant improvements in degumming efficiency. However, the nonhydratable phosphorus contents of the degummed oils were still too high, indicating the need for special processing of damaged oils. Crude lecithin was effective in removing NHP from oil of fresh soybeans, but was ineffective on oils of stored and severely damaged beans.

Oilseed pretreatment in connection with physical refining

AbstractTests have shown that the nonhydratable phosphatides (NHP) arising by the action of phospholipases are not present in significant quantities in commercial soybeans, but that they are formed predominantly only during extraction. By a moisture‐heat treatment of the soy flakes prior to the extraction, this enzyme activity can be almost completely eliminated so that, during the subsequent extraction, an enzymatic change of the oil no longer occurs. In comparison with the extraction of untreated soy flakes, the yield of soy lecithin is doubled; the lecithin has a higher content of phosphatidylchol ine; the crude, degummed soy oil has extraordinarily low NHP contents; and the soy meal tastes less bitter.

Superdegumming, a New Degumming Process and its Effect on the Effluent Problems of Edible Oil Refining

In conventional refining processes most vegetable oils are first waterdegummed and subsequently refined with caustic or with phosphoric acid/caustic. In these treatments also the non-hydratable phosphatides are removed. The effluent problems of edible oil refining are caused mainly by these caustic treatments. Superdegumming is the name of a new degumming process by which the phosphatides can be removed almost completely without any effluent load. Five years of experience with this widely patented degumming process and the subsequent refining of the superdegummed oils are discussed. Especially the effect of this degumming process on the effluent load of edible oil refining is demonstrated.

Quality of oil from damaged soybeans

Abstract and SummaryVarious processing steps were explored in an at‐tempt to improve the quality of oil from field‐ and storage‐damaged soybeans. A crude soybean oil (5.7% free fatty acid) commercially extracted from damaged soybeans was degummed in the laboratory with different reagents: water, phosphoric acid, and acetic anhydride. Two alkali strengths, each at 0.1 and 0.5% excess, were used to refine each degummed oil. After vacuum bleaching (0.5% activated earth) and deodorization (210 C, 3 hr), these oils were un‐acceptable as salad oils. A flavor score of 6.0 or higher characterizes a satisfactory oil. Scores of water and phosphoric acid degummed oils ranged from 4.5 to 5.1, while acetic anhydride degummed oils aver‐aged 5.6. Flavor evaluations of (phosphoric acid de‐gummed) single‐ and double‐refined oils (210 C deodorization) showed that the latter were signifi‐cantly better. Flavor scores increased from 5.0 to about 6.0. To study the effects of deodorization tem‐perature, the crude commercial oil was alkali‐refined, water‐washed and bleached with 0.5% activated earth, but the degumming step was omitted. Flavor evalua‐tion of oil deodorized at 210, 230, and 260 C showed that each temperature increment raised flavor scores significantly. Further evaluations of specially proc‐essed oils (water, phosphoric acid, and acetic anhy‐dride degummed oils given single and double refinings and deodorized at 260 C) showed that deodorization temperature is the most important factor affecting the initial quality of oil from damaged beans. Flavor evaluations showed that hydrogenation and hydro‐genation‐winterization treatments produced oils of high initial quality, but with poorer keeping proper‐ties than oils from normal beans. No evidence was found implicating nonhydratable phosphatides in the oil flavor problem. Iron had a deleterious effect in oils not treated with citric acid during deodorization.