The smell is not good and the appearance helps even less: it is a dark colored and viscous suspension. This is the way that yeast (Saccharomyses cerevisiae) remains after having been used as a fermenting agent for unchaining the molecules in the distilleries at the start of the operation for the processing of alcohol from sugarcane. And, the size of this residue is not small. For every liter of alcohol produced, there is an excess of around 30 grams of dry yeast. If we take into consideration the annual Brazilian production, which reaches 15 billion liters, there is an excess of 450,000 kilos of yeast. All of this residue of little nutritional and commercial value is destined to cattle feed.
The inversion of this picture – oversupply and mediocre use of yeast – began to be implemented in 1998 by the Sugarcane, Sugar and Alcohol Producers Cooperative of the State of São Paulo (Copersucar) and by the Foods Technology Institute (Ital) in a project financed by FAPESP under the Partnership for Technological Innovation (PITE) program. The results presented at the beginning of this year indicate that yeast can not only be made use of in a more efficient manner in animal feed but can also serve as a good alternative for human consumption.
The project, coordinated by the researcher Valdemiro Carlos Sgarbieri, resulted in the formation of four substances derived from yeast: self-smoothed, extract, cellular wall and concentrated protein. All of these by-products contain proteins and can be added to pastas, biscuits, and to bread, as well as to a series of other food products. They are also substances rich in complex B vitamins, micro nutrients and essential minerals such as manganese, magnesium, zinc and iron. They could also substitute the chemical additives in obtaining the flavor, aroma and coloration of processed foods such as, for example, powdered soups. In the pharmaceutical industry, Japan already removes the nucleic acids present in yeast to produce medicine.
With such a wide potential, Copersucar decided to make better use of the residual yeast of its thirty five cooperative mills, responsible for 22% of Brazilian sugar and alcohol production. “Our interest was to add value to the yeast and to find uses for it within human foods”, explains Karl Heinz Leimer, head of the yeast project at Copersucar.
The first partnership for the transfer of technology was with the Santo Antônio mill in the town of Sertãozinho, in the Ribeirão Preto region. The mill is preparing itself to produce the yeast by-products. Leimer evaluates that the investment necessary for the installation of the industrial plant with the capacity for the daily processing of five tons is R$ 500,000.
In the mills the yeast is used in tanks where the must, which is the means of fermentation formed by the sugarcane juice and the yeast, is fermented so that afterwards it can be distilled for alcohol production. However, the process itself multiplies the production of yeast with each cycle of distillation and its removal from the large cauldrons, besides increasing the productivity in alcohol production, and can result in valuable by-products as the study demonstrated. “Normally part of the yeast is removed in each new cycle in a process known as bleeding in the jargon of the industry”, explains Sgarbieri. This biomass is washed to remove impurities and is dried in a piece of equipment named a spray dryer that carries out the drying in the same manner used in the production of powdered milk.
The following process is that of autolysis, when the material is given mechanical agitation in a fermenting machine for twenty four hours. Under these conditions, the hydrolytic enzymes of the cells themselves break through the cell walls and liberate their components that form the self-smoothed. Afterwards, this substance is placed in a centrifuge for the separation of the two by-products, the cellular wall and the extract.
The fourth product, the protein concentrate, is produced by another process. The yeast cells have their walls broken down by a mechanical process and the proteins, after being separated from the fragments of the cellular wall by centrifuging, are solidified by the action of acidic substances. The cellular wall, in powder form, can be used in soups as a thickener and mixed with wheat and corn flours for the production of industrialized snacks.
Uses and advantages
The extract can be commercialized in powder or in a paste to give flavor to the meat in soups. The sale of the extract could give an income of up to R$ 8,00 per kilo, while the current price, with the unimproved yeast, reaches a value of R$ 0,80 per kilo. “With the processed product, it’s possible to attain at the minimum the double of the value obtained today, or up to ten times more for other uses in human foodstuffs or in pharmaceutical products”, says Sgarbieri.
The uses of the yeast by-products covers various segments of the food industry. For example, the extract and the self-smoothed by-product have been tested in the manufacture of sausages, substituting and improving the flavor and aroma of the soya protein. In water biscuits, the same by-products were tested and the results pointed towards a more agreeable flavor and a better texture. The same test was down with spaghetti. The best accepted results occurred with pasta with spinach with its coloration already altered.
Sgarbieri added that the extract was also tested, with good results, in the make up of salads dressings. The testing was done with a free distribution in houses in the region of Campinas. This study marks a new step for the incorporation of innovations in the fruit juice/alcohol sector. The food industry also wins out, as it will shortly have additives extracted from a biomass previously disregarded and of little value.
Development of Technology Looking towards the Use of Yeast Derivatives in Human and Animal Foodstuffs (nº 98/04173-5); Modality Partnership for Technological Innovation (PITE); Coordinator Valdemiro Carlos Sgarbieri – Ital; Investment R$ 62,651.00 and US$ 18,521.00 (FAPESP) and R$ 596,730.00 (Copersucar)