MICROBIOLOGY Study Guide - 2012

CHAPTER 15. FOOD MICROBIOLOGY

15.8. MICROBIOLOGY OF PASTA PRODUCTS

The raw Materials used in pasta production include wheat flour, enrichers, and Water, whose microbiological parameters significantly affect the quality of the finished product.

High standards are set for wheat flour quality: it must be milled from durum wheat, coarsely ground, and have a high gluten content. Moisture content and Temperature are critical factors during storage. Elevated temperatures (30–35 °C) and a flour moisture content exceeding 15% stimulate the Respiration and reproduction processes of microorganisms typically associated with grain and flour. As a result, the technological Properties of the flour deteriorate sharply, gluten quality declines, and the flour acquires a rancid taste and odor. High flour moisture (above 16%) promotes mold growth, rendering it unsuitable for pasta manufacturing.

Pasta production utilizes various enriching additives, such as whole eggs, liquid melange, egg powder, dairy products (dried milk, low-fat cottage cheese), as well as flavoring additives like vegetable pastes, purees, and powders. To prevent secondary contamination of the dough and raw semi-finished products when introducing these enrichers, their quality must strictly comply with established standards.

Fresh pasta products provide a favorable environment for Microbial growth. To prevent microbiological and biochemical spoilage, the products are preserved through dehydration—specifically, drying to a moisture content of no more than 13%. It is well known that microorganisms can proliferate in substrates with a moisture content of 70–85%. When the substrate is dried to 20% residual moisture, Microbial Nutrition and consequently reproduction cease, though enzymatic processes continue. At a moisture content of 8–12%, microorganisms enter anabiosis, a state in which all life processes are slowed down or suspended. In products with 5% residual moisture, internal cellular structures are altered, and most microorganisms perish.

Finished pasta products must have a moisture content not exceeding 13% and an acidity of no more than 3.5–5.0 degrees.

Pasta should be stored in cool, well-ventilated rooms with a relative humidity not exceeding 70%. Packaging materials must have a moisture content of no higher than 15%.

15.8.1. Microbial Spoilage of Pasta Products

If drying regimes and storage conditions are violated, pasta products may undergo microbial spoilage, the types of which are discussed below.

Blistering of pasta products. The surface of the pasta becomes bumpy, and internal voids are revealed upon breaking. Blistering is caused by Heterofermentative lactic acid Bacteria of the species L. breve, L. fermenti, and L. buchneri, which ferment CARBOHYDRATES with The production of acid and gas. They enter the grain, flour, and dough from the soil and plants.

Discoloration of pasta. Purple streaks appear On the surface of the pasta due to the growth of imperfect Fungi of the genus Candida, which are capable of producing a purple pigment. The pasta loses its marketability and becomes unfit for consumption.

Souring. When low-quality raw materials with high bacterial contamination are used, the acidity of the dough increases, resulting in a sour taste in the final product. Lactic acid bacteria are the causative agents of this spoilage.

Molding. An increase in pasta moisture to 15–16% leads to mold development. The following species of filamentous fungi can proliferate on the surface of pasta products: Aspergillus clavatus, A. candidus, Penicillium puberulum, Rhizopus nigricans, Mucor racemosus.