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Prevention and correction of quality defects in Hispanic cheeses

Dr. Mali Reddy

Dr. Mali Reddy serves as president of the American Dairy and Food Consulting Laboratories and International Media and Cultures (IMAC Inc.), Denver, Colo. He holds several degrees including M.S. and Ph.D. degrees from Iowa State University in food technology and microbiology. He is a guest columnist for this week’s issue of Cheese Market News®.

In my last three columns, I wrote about protecting Hispanic- type cheeses from pathogens and also from product defects such as pastiness and gassy defect. In this column, I am writing about the genesis of other common defects in fresh Hispanic cheeses and their possible remedies. This article does not cover Hispanic melting cheeses or Cotija.

Unlike other cheeses, Hispanic fresh cheeses are mild in flavor and are usually white or off-white in color. As the name implies, Queso Blanco means “white cheese.” It has a fresh, slightly salty flavor and somewhat crumbly texture. It is used either as a fried snack or in tossed salads. The expectation of the customer is that the cheese, when fried, should not melt and should brown slightly.

Queso Fresco is a moist, soft and fine-grained cheese with a fresh dairy note (milky flavor). It crumbles more readily than Queso Blanco. Queso Fresco is used as topping or a filling in cooked dishes like enchiladas. Its color is white to slightly off-white.

Queso Para Freir is much saltier than Queso Blanco and, as its name implies, is frying cheese. The color of the sliced or cubed cheese upon frying should be golden brown.

Panela is more like fresh Mozzarella and served along with fruit or used in sandwiches.

All of these cheeses should have a fresh milk flavor, excellent white color, and should only soften but not melt upon heating. Consequently, unlike their fermented counterpart cheeses, the physical appearance (white and appealing), fresh flavor (milky flavor), slight browning to golden browning upon frying, and non-melting character upon frying are of extreme importance.

The following are some of the general defects encountered with the above specified fresh Hispanic cheeses: lack of fresh milky flavor; distinct aged cheese flavor; off-color; excessive melting upon frying; too much browning upon frying or grilling; cheesy aftertaste; bitterness; offensive putrid smell; yeasty odor; and weeping or wheying off in the package.

The color of the cheese is dictated by the degree of proteolysis, retention of calcium in the cheese, and the amount of liberation of simple sugars. Some degree of proteolysis is essential and is mainly due to coagulating enzymes. Microbial rennet is more proteolytic than veal or comparable genetically-modified rennet. Whereas, the liberation of simple sugars is mainly due to bacterial enzymes. Consequently, if starter cultures have to be used, care must be taken to select low acid producers to eliminate excess liberation of simple sugars. In fresh Hispanic-type cheeses the pH must be sufficiently high, an indication of high insoluble calcium in the curd matrix, which imparts a nice white color to the cheese. If a customer complains regarding the color of the cheese, i.e. slightly darker, one should look into coagulating enzymes, type of cultures (if cultures are used), type and number of residual heat-resistant adventitious flora, and also the post pasteurization contaminants in the finished cheese.

When it comes to integrity of the block, the cheese must not exhibit any signs of free liquid whey stagnant in the package. Wheying off is directly related to the degree of proteolysis either due to coagulant used or the starter and/or associated micro flora in the cheese. Sometimes physical factors may also contribute to this defect. However, physical factors are more easily controlled than the microbial or enzyme-related problems.

With regard to flavor and taste, fresh Hispanic cheeses must have delicate fresh milk flavor. As the name implies, the importance of freshness of the milk cannot be ignored. The raw milk must be protected from the excess growth of psychrotrophic bacteria. These organisms liberate proteolytic and lipolytic enzymes, which will resist pasteurization and thus start deteriorating the cheese. Since fresh Hispanic cheeses have mild flavors, any degree of excess proteolysis and lipolysis will induce fermented cheesy flavors, which will cover up the delicate fresh milk flavor. I strongly recommend usage of milk silo cultures to retard the growth of psychrotrophic bacteria while the milk is in silos.

Fresh Hispanic cheeses also should not be bitter or acidic. The acidic taste results from excess production of lactic acid by either pasteurization resistant adventitious flora or due to use of high acid producing starters. Specialty starter cultures must be used to eliminate excess acid production. Bulk starter also can be used in the Hispanic-type cheeses.

However, the acid production by such starter must be significantly low because of the delicate nature of the cheese. One way to accomplish this is to grow starter cultures in the liquid media and then subject them to high heat (perhaps 145 F) to attenuate or weaken the casein and lactose-breaking enzymes. Such heat-shocked starter maintains the pH and at the same time protects the cheese from excess production of acid or protein breakdown in addition to improving safety. Such heat-attenuated bulk starters will not impart a cheesy flavor.

Another way to accomplish this is by adding bulk starter to raw milk, and then pasteurizing the milk. This way only heat-resistant subtle starter enzymes and heat-injured starter cultures will give the cheese delicate flavor without destroying other attributes.

Some of the cheese cultures also give bitterness by liberating bitter peptides. Thus, care must be taken to eliminate such cultures. The bitterness defect can also be reduced with the use of selected de-bitterase enzymes of either starter or non-starter origin. The same thing holds true with some coagulants.

Another culprit which alters taste and flavor of the cheese is yeast, which must be minimized or eliminated. Hispanic cheese plants have to experiment to arrive at the best possible coagulants, yeast inhibitors and starter systems that will work in harmony to eliminate the taste and flavor defects in the cheese. Use of the bulk starter (primary and/or secondary) with heat attenuation is the best way not only to improve quality of cheese but also the yields. Indirectly, it will also greatly improve the quality of whey.

Finally, the functionality of fresh Hispanic cheese in the finished food is of prime importance. In the case of Hispanic-type cheeses such as Queso Blanco and Queso Para Frier, the cheese should not melt upon frying and it should develop some amount of browning (golden brown). More research is required in this arena to standardize the functional qualities of Hispanic cheeses.

Considering the surge in demand for fresh Hispanic cheeses, a delicate and sophisticated enzyme and microbial (starter) technology should be developed, starting from raw milk to the finished product, to produce the safest cheeses with least defects. Such a technology should be sound, simple and easy to implement with a high degree of reproducibility. Of course, the level of sanitation and good manufacturing practices should never be ignored, especially when you are dealing with fresh and highly perishable Hispanic cheeses.

CMN

The views expressed by CMN’s guest columnists are their own opinions and do not necessarily reflect those of Cheese Market News®.

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